[NC-1582] Added iBFT 2.0 Hashing functions and header validation rules (#119)

6 years ago · 77a3df36ae
parent 8e9a1ddc72
commit 77a3df36ae
20 changed files with 1602 additions and 39 deletions
--- a/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/ValidatorVote.java
+++ b/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/ValidatorVote.java
@ -0,0 +1,19 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.common;
+
+public interface ValidatorVote {
+  boolean isAddVote();
+
+  boolean isDropVote();
+}
--- a/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/VoteTally.java
+++ b/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/VoteTally.java
@ -54,15 +54,16 @@ public class VoteTally implements ValidatorProvider {
   *
   * @param proposer the address of the validator casting the vote via block proposal
   * @param subject the validator the vote is about
-   * @param voteType the type of vote, either add or drop
+   * @param validatorVote the type of vote, either add or drop
   */
-  public void addVote(final Address proposer, final Address subject, final VoteType voteType) {
+  public void addVote(
+      final Address proposer, final Address subject, final ValidatorVote validatorVote) {
    final Set<Address> addVotesForSubject =
        addVotesBySubject.computeIfAbsent(subject, target -> new HashSet<>());
    final Set<Address> removeVotesForSubject =
        removeVotesBySubject.computeIfAbsent(subject, target -> new HashSet<>());

-    if (voteType == VoteType.ADD) {
+    if (validatorVote.isAddVote()) {
      addVotesForSubject.add(proposer);
      removeVotesForSubject.remove(proposer);
    } else {
--- a/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/VoteType.java
+++ b/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/VoteType.java
@ -14,7 +14,7 @@ package tech.pegasys.pantheon.consensus.common;

 import java.util.Optional;

-public enum VoteType {
+public enum VoteType implements ValidatorVote {
  ADD(0xFFFFFFFFFFFFFFFFL),
  DROP(0x0L);

@ -36,4 +36,14 @@ public enum VoteType {
    }
    return Optional.empty();
  }
+
+  @Override
+  public boolean isAddVote() {
+    return this.equals(ADD);
+  }
+
+  @Override
+  public boolean isDropVote() {
+    return this.equals(DROP);
+  }
 }
--- a/consensus/common/src/test/java/net/consensys/pantheon/consensus/common/VoteTypeTest.java
+++ b/consensus/common/src/test/java/net/consensys/pantheon/consensus/common/VoteTypeTest.java
@ -0,0 +1,30 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package net.consensys.pantheon.consensus.common;
+
+import static org.assertj.core.api.Java6Assertions.assertThat;
+
+import tech.pegasys.pantheon.consensus.common.VoteType;
+
+import org.junit.Test;
+
+public class VoteTypeTest {
+  @Test
+  public void testValidatorVoteMethodImplementation() {
+    assertThat(VoteType.ADD.isAddVote()).isTrue();
+    assertThat(VoteType.ADD.isDropVote()).isFalse();
+
+    assertThat(VoteType.DROP.isAddVote()).isFalse();
+    assertThat(VoteType.DROP.isDropVote()).isTrue();
+  }
+}
--- a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/IbftBlockHashing.java
+++ b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/IbftBlockHashing.java
@ -0,0 +1,95 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.ibft;
+
+import tech.pegasys.pantheon.ethereum.core.Address;
+import tech.pegasys.pantheon.ethereum.core.BlockHeader;
+import tech.pegasys.pantheon.ethereum.core.BlockHeaderBuilder;
+import tech.pegasys.pantheon.ethereum.core.Hash;
+import tech.pegasys.pantheon.ethereum.core.Util;
+import tech.pegasys.pantheon.ethereum.rlp.BytesValueRLPOutput;
+import tech.pegasys.pantheon.util.bytes.BytesValue;
+
+import java.util.List;
+import java.util.function.Supplier;
+import java.util.stream.Collectors;
+
+public class IbftBlockHashing {
+
+  /**
+   * Constructs a hash of the block header suitable for signing as a committed seal. The extra data
+   * in the hash uses an empty list for the committed seals.
+   *
+   * @param header The header for which a proposer seal is to be calculated (with or without extra
+   *     data)
+   * @param ibftExtraData The extra data block which is to be inserted to the header once seal is
+   *     calculated
+   * @return the hash of the header including the validator and proposer seal in the extra data
+   */
+  public static Hash calculateDataHashForCommittedSeal(
+      final BlockHeader header, final IbftExtraData ibftExtraData) {
+    return Hash.hash(serializeHeader(header, ibftExtraData::encodeWithoutCommitSeals));
+  }
+
+  /**
+   * Constructs a hash of the block header, but omits the committerSeals and sets round number to 0
+   * (as these change on each of the potentially circulated blocks at the current chain height).
+   *
+   * @param header The header for which a block hash is to be calculated
+   * @return the hash of the header to be used when referencing the header on the blockchain
+   */
+  public static Hash calculateHashOfIbftBlockOnChain(final BlockHeader header) {
+    final IbftExtraData ibftExtraData = IbftExtraData.decode(header.getExtraData());
+    return Hash.hash(
+        serializeHeader(header, ibftExtraData::encodeWithoutCommitSealsAndRoundNumber));
+  }
+
+  /**
+   * Recovers the {@link Address} for each validator that contributed a committed seal to the block.
+   *
+   * @param header the block header that was signed by the committed seals
+   * @param ibftExtraData the parsed {@link IbftExtraData} from the header
+   * @return the addresses of validators that provided a committed seal
+   */
+  public static List<Address> recoverCommitterAddresses(
+      final BlockHeader header, final IbftExtraData ibftExtraData) {
+    final Hash committerHash =
+        IbftBlockHashing.calculateDataHashForCommittedSeal(header, ibftExtraData);
+
+    return ibftExtraData
+        .getSeals()
+        .stream()
+        .map(p -> Util.signatureToAddress(p, committerHash))
+        .collect(Collectors.toList());
+  }
+
+  private static BytesValue serializeHeader(
+      final BlockHeader header, final Supplier<BytesValue> extraDataSerializer) {
+
+    // create a block header which is a copy of the header supplied as parameter except of the
+    // extraData field
+    BlockHeaderBuilder builder = BlockHeaderBuilder.fromHeader(header);
+    builder.blockHashFunction(IbftBlockHashing::calculateHashOfIbftBlockOnChain);
+
+    // set the extraData field using the supplied extraDataSerializer if the block height is not 0
+    if (header.getNumber() == 0) {
+      builder.extraData(header.getExtraData());
+    } else {
+      builder.extraData(extraDataSerializer.get());
+    }
+
+    final BytesValueRLPOutput out = new BytesValueRLPOutput();
+    builder.buildBlockHeader().writeTo(out);
+    return out.encoded();
+  }
+}
--- a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/IbftBlockHeaderValidationRulesetFactory.java
+++ b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/IbftBlockHeaderValidationRulesetFactory.java
@ -0,0 +1,76 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.ibft;
+
+import tech.pegasys.pantheon.consensus.ibft.headervalidationrules.IbftCoinbaseValidationRule;
+import tech.pegasys.pantheon.consensus.ibft.headervalidationrules.IbftExtraDataValidationRule;
+import tech.pegasys.pantheon.ethereum.core.BlockHeader;
+import tech.pegasys.pantheon.ethereum.core.Hash;
+import tech.pegasys.pantheon.ethereum.mainnet.BlockHeaderValidator;
+import tech.pegasys.pantheon.ethereum.mainnet.headervalidationrules.AncestryValidationRule;
+import tech.pegasys.pantheon.ethereum.mainnet.headervalidationrules.ConstantFieldValidationRule;
+import tech.pegasys.pantheon.ethereum.mainnet.headervalidationrules.GasLimitRangeAndDeltaValidationRule;
+import tech.pegasys.pantheon.ethereum.mainnet.headervalidationrules.GasUsageValidationRule;
+import tech.pegasys.pantheon.ethereum.mainnet.headervalidationrules.TimestampBoundedByFutureParameter;
+import tech.pegasys.pantheon.ethereum.mainnet.headervalidationrules.TimestampMoreRecentThanParent;
+import tech.pegasys.pantheon.util.uint.UInt256;
+
+public class IbftBlockHeaderValidationRulesetFactory {
+
+  /**
+   * Produces a BlockHeaderValidator configured for assessing ibft block headers which are to form
+   * part of the BlockChain (i.e. not proposed blocks, which do not contain commit seals)
+   *
+   * @param secondsBetweenBlocks the minimum number of seconds which must elapse between blocks.
+   * @return BlockHeaderValidator configured for assessing ibft block headers
+   */
+  public static BlockHeaderValidator<IbftContext> ibftBlockHeaderValidator(
+      final long secondsBetweenBlocks) {
+    return createValidator(secondsBetweenBlocks, true);
+  }
+
+  /**
+   * Produces a BlockHeaderValidator configured for assessing IBFT proposed blocks (i.e. blocks
+   * which need to be vetted by the validators, and do not contain commit seals).
+   *
+   * @param secondsBetweenBlocks the minimum number of seconds which must elapse between blocks.
+   * @return BlockHeaderValidator configured for assessing ibft block headers
+   */
+  public static BlockHeaderValidator<IbftContext> ibftProposedBlockValidator(
+      final long secondsBetweenBlocks) {
+    return createValidator(secondsBetweenBlocks, false);
+  }
+
+  private static BlockHeaderValidator<IbftContext> createValidator(
+      final long secondsBetweenBlocks, final boolean validateCommitSeals) {
+    return new BlockHeaderValidator.Builder<IbftContext>()
+        .addRule(new AncestryValidationRule())
+        .addRule(new GasUsageValidationRule())
+        .addRule(new GasLimitRangeAndDeltaValidationRule(5000, 0x7fffffffffffffffL))
+        .addRule(new TimestampBoundedByFutureParameter(1))
+        .addRule(new TimestampMoreRecentThanParent(secondsBetweenBlocks))
+        .addRule(
+            new ConstantFieldValidationRule<>(
+                "MixHash", BlockHeader::getMixHash, IbftHelpers.EXPECTED_MIX_HASH))
+        .addRule(
+            new ConstantFieldValidationRule<>(
+                "OmmersHash", BlockHeader::getOmmersHash, Hash.EMPTY_LIST_HASH))
+        .addRule(
+            new ConstantFieldValidationRule<>(
+                "Difficulty", BlockHeader::getDifficulty, UInt256.ONE))
+        .addRule(new ConstantFieldValidationRule<>("Nonce", BlockHeader::getNonce, 0L))
+        .addRule(new IbftExtraDataValidationRule(validateCommitSeals))
+        .addRule(new IbftCoinbaseValidationRule())
+        .build();
+  }
+}
--- a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/Ibft2ExtraData.java
+++ b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/Ibft2ExtraData.java
@ -29,7 +29,7 @@ import java.util.Optional;
 * Represents the data structure stored in the extraData field of the BlockHeader used when
 * operating under an IBFT 2.0 consensus mechanism.
 */
-public class Ibft2ExtraData {
+public class IbftExtraData {

  public static final int EXTRA_VANITY_LENGTH = 32;

@ -39,7 +39,7 @@ public class Ibft2ExtraData {
  private final int round;
  private final List<Address> validators;

-  public Ibft2ExtraData(
+  public IbftExtraData(
      final BytesValue vanityData,
      final List<Signature> seals,
      final Optional<Vote> vote,
@ -57,7 +57,7 @@ public class Ibft2ExtraData {
    this.vote = vote;
  }

-  public static Ibft2ExtraData decode(final BytesValue input) {
+  public static IbftExtraData decode(final BytesValue input) {
    checkArgument(
        input.size() > EXTRA_VANITY_LENGTH,
        "Invalid BytesValue supplied - too short to produce a valid IBFT Extra Data object.");
@ -78,10 +78,29 @@ public class Ibft2ExtraData {
    final List<Signature> seals = rlpInput.readList(rlp -> Signature.decode(rlp.readBytesValue()));
    rlpInput.leaveList();

-    return new Ibft2ExtraData(vanityData, seals, vote, round, validators);
+    return new IbftExtraData(vanityData, seals, vote, round, validators);
  }

  public BytesValue encode() {
+    return encode(EncodingType.ALL);
+  }
+
+  public BytesValue encodeWithoutCommitSeals() {
+    return encode(EncodingType.EXCLUDE_COMMIT_SEALS);
+  }
+
+  public BytesValue encodeWithoutCommitSealsAndRoundNumber() {
+    return encode(EncodingType.EXCLUDE_COMMIT_SEALS_AND_ROUND_NUMBER);
+  }
+
+  private enum EncodingType {
+    ALL,
+    EXCLUDE_COMMIT_SEALS,
+    EXCLUDE_COMMIT_SEALS_AND_ROUND_NUMBER
+  }
+
+  private BytesValue encode(final EncodingType encodingType) {
+
    final BytesValueRLPOutput encoder = new BytesValueRLPOutput();
    encoder.startList();
    encoder.writeBytesValue(vanityData);
@ -91,8 +110,13 @@ public class Ibft2ExtraData {
    } else {
      encoder.writeNull();
    }
-    encoder.writeInt(round);
-    encoder.writeList(seals, (committer, rlp) -> rlp.writeBytesValue(committer.encodedBytes()));
+
+    if (encodingType != EncodingType.EXCLUDE_COMMIT_SEALS_AND_ROUND_NUMBER) {
+      encoder.writeInt(round);
+      if (encodingType != EncodingType.EXCLUDE_COMMIT_SEALS) {
+        encoder.writeList(seals, (committer, rlp) -> rlp.writeBytesValue(committer.encodedBytes()));
+      }
+    }
    encoder.endList();

    return encoder.encoded();
--- a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/IbftHelpers.java
+++ b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/IbftHelpers.java
@ -0,0 +1,26 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.ibft;
+
+import tech.pegasys.pantheon.ethereum.core.Hash;
+import tech.pegasys.pantheon.ethereum.core.Util;
+
+public class IbftHelpers {
+
+  public static final Hash EXPECTED_MIX_HASH =
+      Hash.fromHexString("0x63746963616c2062797a616e74696e65206661756c7420746f6c6572616e6365");
+
+  public static int calculateRequiredValidatorQuorum(final int validatorCount) {
+    return Util.fastDivCeiling(2 * validatorCount, 3);
+  }
+}
--- a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/IbftVoteType.java
+++ b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/IbftVoteType.java
@ -12,11 +12,12 @@
 */
 package tech.pegasys.pantheon.consensus.ibft;

+import tech.pegasys.pantheon.consensus.common.ValidatorVote;
 import tech.pegasys.pantheon.ethereum.rlp.RLPException;
 import tech.pegasys.pantheon.ethereum.rlp.RLPInput;
 import tech.pegasys.pantheon.ethereum.rlp.RLPOutput;

-public enum IbftVoteType {
+public enum IbftVoteType implements ValidatorVote {
  ADD((byte) 0xFF),
  DROP((byte) 0x00);

@ -44,4 +45,14 @@ public enum IbftVoteType {
  public void writeTo(final RLPOutput rlpOutput) {
    rlpOutput.writeByte(voteValue);
  }
+
+  @Override
+  public boolean isAddVote() {
+    return this.equals(ADD);
+  }
+
+  @Override
+  public boolean isDropVote() {
+    return this.equals(DROP);
+  }
 }
--- a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/headervalidationrules/IbftCoinbaseValidationRule.java
+++ b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/headervalidationrules/IbftCoinbaseValidationRule.java
@ -0,0 +1,53 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.ibft.headervalidationrules;
+
+import tech.pegasys.pantheon.consensus.common.ValidatorProvider;
+import tech.pegasys.pantheon.consensus.ibft.IbftContext;
+import tech.pegasys.pantheon.ethereum.ProtocolContext;
+import tech.pegasys.pantheon.ethereum.core.Address;
+import tech.pegasys.pantheon.ethereum.core.BlockHeader;
+import tech.pegasys.pantheon.ethereum.mainnet.AttachedBlockHeaderValidationRule;
+
+import java.util.Collection;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+/**
+ * Ensures that the coinbase (which corresponds to the block proposer) is included in the list of
+ * validators
+ */
+public class IbftCoinbaseValidationRule implements AttachedBlockHeaderValidationRule<IbftContext> {
+
+  private static final Logger LOGGER = LogManager.getLogger(IbftCoinbaseValidationRule.class);
+
+  @Override
+  public boolean validate(
+      final BlockHeader header,
+      final BlockHeader parent,
+      final ProtocolContext<IbftContext> context) {
+
+    final ValidatorProvider validatorProvider = context.getConsensusState().getVoteTally();
+    Address proposer = header.getCoinbase();
+
+    final Collection<Address> storedValidators = validatorProvider.getCurrentValidators();
+
+    if (!storedValidators.contains(proposer)) {
+      LOGGER.trace("Block proposer is not a member of the validators.");
+      return false;
+    }
+
+    return true;
+  }
+}
--- a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/headervalidationrules/IbftExtraDataValidationRule.java
+++ b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/headervalidationrules/IbftExtraDataValidationRule.java
@ -0,0 +1,124 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.ibft.headervalidationrules;
+
+import static tech.pegasys.pantheon.consensus.ibft.IbftHelpers.calculateRequiredValidatorQuorum;
+
+import tech.pegasys.pantheon.consensus.common.ValidatorProvider;
+import tech.pegasys.pantheon.consensus.ibft.IbftBlockHashing;
+import tech.pegasys.pantheon.consensus.ibft.IbftContext;
+import tech.pegasys.pantheon.consensus.ibft.IbftExtraData;
+import tech.pegasys.pantheon.ethereum.ProtocolContext;
+import tech.pegasys.pantheon.ethereum.core.Address;
+import tech.pegasys.pantheon.ethereum.core.BlockHeader;
+import tech.pegasys.pantheon.ethereum.mainnet.AttachedBlockHeaderValidationRule;
+import tech.pegasys.pantheon.ethereum.rlp.RLPException;
+
+import java.util.Collection;
+import java.util.List;
+
+import com.google.common.collect.Iterables;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+/**
+ * Ensures the byte content of the extraData field can be deserialised into an appropriate
+ * structure, and that the structure created contains data matching expectations from preceding
+ * blocks.
+ */
+public class IbftExtraDataValidationRule implements AttachedBlockHeaderValidationRule<IbftContext> {
+
+  private static final Logger LOGGER = LogManager.getLogger(IbftExtraDataValidationRule.class);
+
+  private final boolean validateCommitSeals;
+
+  public IbftExtraDataValidationRule(final boolean validateCommitSeals) {
+    this.validateCommitSeals = validateCommitSeals;
+  }
+
+  @Override
+  public boolean validate(
+      final BlockHeader header,
+      final BlockHeader parent,
+      final ProtocolContext<IbftContext> context) {
+    return validateExtraData(header, context);
+  }
+
+  /**
+   * Responsible for determining the validity of the extra data field. Ensures:
+   *
+   * <ul>
+   *   <li>Bytes in the extra data field can be decoded as per IBFT specification
+   *   <li>Proposer (derived from the proposerSeal) is a member of the validators
+   *   <li>Committers (derived from committerSeals) are all members of the validators
+   * </ul>
+   *
+   * @param header the block header containing the extraData to be validated.
+   * @return True if the extraData successfully produces an IstanbulExtraData object, false
+   *     otherwise
+   */
+  private boolean validateExtraData(
+      final BlockHeader header, final ProtocolContext<IbftContext> context) {
+    try {
+      final ValidatorProvider validatorProvider = context.getConsensusState().getVoteTally();
+      final IbftExtraData ibftExtraData = IbftExtraData.decode(header.getExtraData());
+
+      final Collection<Address> storedValidators = validatorProvider.getCurrentValidators();
+
+      if (validateCommitSeals) {
+        final List<Address> committers =
+            IbftBlockHashing.recoverCommitterAddresses(header, ibftExtraData);
+        if (!validateCommitters(committers, storedValidators)) {
+          return false;
+        }
+      }
+
+      if (!Iterables.elementsEqual(ibftExtraData.getValidators(), storedValidators)) {
+        LOGGER.trace(
+            "Incorrect validators. Expected {} but got {}.",
+            storedValidators,
+            ibftExtraData.getValidators());
+        return false;
+      }
+
+    } catch (final RLPException ex) {
+      LOGGER.trace("ExtraData field was unable to be deserialised into an IBFT Struct.", ex);
+      return false;
+    } catch (final IllegalArgumentException ex) {
+      LOGGER.trace("Failed to verify extra data", ex);
+      return false;
+    }
+
+    return true;
+  }
+
+  private boolean validateCommitters(
+      final Collection<Address> committers, final Collection<Address> storedValidators) {
+
+    final int minimumSealsRequired = calculateRequiredValidatorQuorum(storedValidators.size());
+    if (committers.size() < minimumSealsRequired) {
+      LOGGER.trace(
+          "Insufficient committers to seal block. (Required {}, received {})",
+          minimumSealsRequired,
+          committers.size());
+      return false;
+    }
+
+    if (!storedValidators.containsAll(committers)) {
+      LOGGER.trace("Not all committers are in the locally maintained validator list.");
+      return false;
+    }
+
+    return true;
+  }
+}
--- a/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/IbftBlockHashingTest.java
+++ b/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/IbftBlockHashingTest.java
@ -0,0 +1,180 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.ibft;
+
+import static java.util.Collections.emptyList;
+import static org.assertj.core.api.Java6Assertions.assertThat;
+
+import tech.pegasys.pantheon.crypto.SECP256K1;
+import tech.pegasys.pantheon.crypto.SECP256K1.KeyPair;
+import tech.pegasys.pantheon.crypto.SECP256K1.PrivateKey;
+import tech.pegasys.pantheon.crypto.SECP256K1.Signature;
+import tech.pegasys.pantheon.ethereum.core.Address;
+import tech.pegasys.pantheon.ethereum.core.BlockHeader;
+import tech.pegasys.pantheon.ethereum.core.BlockHeaderBuilder;
+import tech.pegasys.pantheon.ethereum.core.Hash;
+import tech.pegasys.pantheon.ethereum.core.LogsBloomFilter;
+import tech.pegasys.pantheon.ethereum.core.Util;
+import tech.pegasys.pantheon.ethereum.rlp.BytesValueRLPOutput;
+import tech.pegasys.pantheon.util.bytes.BytesValue;
+import tech.pegasys.pantheon.util.uint.UInt256;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+import org.junit.Test;
+
+public class IbftBlockHashingTest {
+
+  private static final List<KeyPair> COMMITTERS_KEY_PAIRS = committersKeyPairs();
+  private static final List<Address> VALIDATORS =
+      Arrays.asList(Address.fromHexString("1"), Address.fromHexString("2"));
+  private static final Optional<Vote> VOTE = Optional.of(Vote.authVote(Address.fromHexString("3")));
+  private static final int ROUND = 0x00FEDCBA;
+  private static final BytesValue VANITY_DATA = vanityBytes();
+
+  private static final BlockHeader HEADER_TO_BE_HASHED = headerToBeHashed();
+  private static final Hash EXPECTED_HEADER_HASH = expectedHeaderHash();
+
+  @Test
+  public void testCalculateHashOfIbft2BlockOnChain() {
+    Hash actualHeaderHash = IbftBlockHashing.calculateHashOfIbftBlockOnChain(HEADER_TO_BE_HASHED);
+    assertThat(actualHeaderHash).isEqualTo(EXPECTED_HEADER_HASH);
+  }
+
+  @Test
+  public void testRecoverCommitterAddresses() {
+    List<Address> actualCommitterAddresses =
+        IbftBlockHashing.recoverCommitterAddresses(
+            HEADER_TO_BE_HASHED, IbftExtraData.decode(HEADER_TO_BE_HASHED.getExtraData()));
+
+    List<Address> expectedCommitterAddresses =
+        COMMITTERS_KEY_PAIRS
+            .stream()
+            .map(keyPair -> Util.publicKeyToAddress(keyPair.getPublicKey()))
+            .collect(Collectors.toList());
+
+    assertThat(actualCommitterAddresses).isEqualTo(expectedCommitterAddresses);
+  }
+
+  @Test
+  public void testCalculateDataHashForCommittedSeal() {
+    Hash dataHahsForCommittedSeal =
+        IbftBlockHashing.calculateDataHashForCommittedSeal(
+            HEADER_TO_BE_HASHED, IbftExtraData.decode(HEADER_TO_BE_HASHED.getExtraData()));
+
+    BlockHeaderBuilder builder = setHeaderFieldsExceptForExtraData();
+
+    List<Signature> commitSeals =
+        COMMITTERS_KEY_PAIRS
+            .stream()
+            .map(keyPair -> SECP256K1.sign(dataHahsForCommittedSeal, keyPair))
+            .collect(Collectors.toList());
+
+    IbftExtraData extraDataWithCommitSeals =
+        new IbftExtraData(VANITY_DATA, commitSeals, VOTE, ROUND, VALIDATORS);
+
+    builder.extraData(extraDataWithCommitSeals.encode());
+    BlockHeader actualHeader = builder.buildBlockHeader();
+    assertThat(actualHeader).isEqualTo(HEADER_TO_BE_HASHED);
+  }
+
+  private static List<KeyPair> committersKeyPairs() {
+    return IntStream.rangeClosed(1, 4)
+        .mapToObj(i -> KeyPair.create(PrivateKey.create(UInt256.of(i).getBytes())))
+        .collect(Collectors.toList());
+  }
+
+  private static BlockHeaderBuilder setHeaderFieldsExceptForExtraData() {
+    final BlockHeaderBuilder builder = new BlockHeaderBuilder();
+    builder.parentHash(
+        Hash.fromHexString("0xa7762d3307dbf2ae6a1ae1b09cf61c7603722b2379731b6b90409cdb8c8288a0"));
+    builder.ommersHash(
+        Hash.fromHexString("0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347"));
+    builder.coinbase(Address.fromHexString("0x0000000000000000000000000000000000000000"));
+    builder.stateRoot(
+        Hash.fromHexString("0xca07595b82f908822971b7e848398e3395e59ee52565c7ef3603df1a1fa7bc80"));
+    builder.transactionsRoot(
+        Hash.fromHexString("0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421"));
+    builder.receiptsRoot(
+        Hash.fromHexString("0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421"));
+    builder.logsBloom(
+        LogsBloomFilter.fromHexString(
+            "0x000000000000000000000000000000000000000000000000"
+                + "00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                + "00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                + "00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                + "00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                + "00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                + "0000"));
+    builder.difficulty(UInt256.ONE);
+    builder.number(1);
+    builder.gasLimit(4704588);
+    builder.gasUsed(0);
+    builder.timestamp(1530674616);
+    builder.mixHash(
+        Hash.fromHexString("0x63746963616c2062797a616e74696e65206661756c7420746f6c6572616e6365"));
+    builder.nonce(0);
+    builder.blockHashFunction(IbftBlockHashing::calculateHashOfIbftBlockOnChain);
+    return builder;
+  }
+
+  private static BytesValue vanityBytes() {
+    final byte[] vanity_bytes = new byte[32];
+    for (int i = 0; i < vanity_bytes.length; i++) {
+      vanity_bytes[i] = (byte) i;
+    }
+    return BytesValue.wrap(vanity_bytes);
+  }
+
+  private static BlockHeader headerToBeHashed() {
+    BlockHeaderBuilder builder = setHeaderFieldsExceptForExtraData();
+
+    builder.extraData(
+        new IbftExtraData(VANITY_DATA, emptyList(), VOTE, ROUND, VALIDATORS)
+            .encodeWithoutCommitSeals());
+
+    BytesValueRLPOutput rlpForHeaderFroCommittersSigning = new BytesValueRLPOutput();
+    builder.buildBlockHeader().writeTo(rlpForHeaderFroCommittersSigning);
+
+    List<Signature> commitSeals =
+        COMMITTERS_KEY_PAIRS
+            .stream()
+            .map(
+                keyPair ->
+                    SECP256K1.sign(Hash.hash(rlpForHeaderFroCommittersSigning.encoded()), keyPair))
+            .collect(Collectors.toList());
+
+    IbftExtraData extraDataWithCommitSeals =
+        new IbftExtraData(VANITY_DATA, commitSeals, VOTE, ROUND, VALIDATORS);
+
+    builder.extraData(extraDataWithCommitSeals.encode());
+    return builder.buildBlockHeader();
+  }
+
+  private static Hash expectedHeaderHash() {
+    BlockHeaderBuilder builder = setHeaderFieldsExceptForExtraData();
+
+    builder.extraData(
+        new IbftExtraData(VANITY_DATA, emptyList(), VOTE, 0, VALIDATORS)
+            .encodeWithoutCommitSealsAndRoundNumber());
+
+    BytesValueRLPOutput rlpOutput = new BytesValueRLPOutput();
+    builder.buildBlockHeader().writeTo(rlpOutput);
+
+    return Hash.hash(rlpOutput.encoded());
+  }
+}
--- a/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/IbftBlockHeaderValidationRulesetFactoryTest.java
+++ b/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/IbftBlockHeaderValidationRulesetFactoryTest.java
@ -0,0 +1,318 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.ibft;
+
+import static java.util.Collections.emptyList;
+import static java.util.Collections.singletonList;
+import static org.assertj.core.api.Assertions.assertThat;
+import static tech.pegasys.pantheon.consensus.ibft.IbftProtocolContextFixture.protocolContext;
+
+import tech.pegasys.pantheon.crypto.SECP256K1.KeyPair;
+import tech.pegasys.pantheon.ethereum.core.Address;
+import tech.pegasys.pantheon.ethereum.core.BlockHeader;
+import tech.pegasys.pantheon.ethereum.core.BlockHeaderTestFixture;
+import tech.pegasys.pantheon.ethereum.core.Hash;
+import tech.pegasys.pantheon.ethereum.core.Util;
+import tech.pegasys.pantheon.ethereum.mainnet.BlockHeaderValidator;
+import tech.pegasys.pantheon.ethereum.mainnet.HeaderValidationMode;
+import tech.pegasys.pantheon.util.bytes.BytesValue;
+import tech.pegasys.pantheon.util.uint.UInt256;
+
+import java.util.List;
+import java.util.Optional;
+
+import org.junit.Test;
+
+public class IbftBlockHeaderValidationRulesetFactoryTest {
+
+  @Test
+  public void ibftValidateHeaderPasses() {
+    final KeyPair proposerKeyPair = KeyPair.generate();
+    final Address proposerAddress = Util.publicKeyToAddress(proposerKeyPair.getPublicKey());
+
+    final List<Address> validators = singletonList(proposerAddress);
+
+    final BlockHeader parentHeader =
+        getPresetHeaderBuilder(1, proposerKeyPair, validators, null).buildHeader();
+    final BlockHeader blockHeader =
+        getPresetHeaderBuilder(2, proposerKeyPair, validators, parentHeader).buildHeader();
+
+    final BlockHeaderValidator<IbftContext> validator =
+        IbftBlockHeaderValidationRulesetFactory.ibftBlockHeaderValidator(5);
+
+    assertThat(
+            validator.validateHeader(
+                blockHeader, parentHeader, protocolContext(validators), HeaderValidationMode.FULL))
+        .isTrue();
+  }
+
+  @Test
+  public void ibftValidateHeaderFailsOnExtraData() {
+    final KeyPair proposerKeyPair = KeyPair.generate();
+    final Address proposerAddress = Util.publicKeyToAddress(proposerKeyPair.getPublicKey());
+
+    final List<Address> validators = singletonList(proposerAddress);
+
+    final BlockHeader parentHeader =
+        getPresetHeaderBuilder(1, proposerKeyPair, validators, null).buildHeader();
+    final BlockHeader blockHeader =
+        getPresetHeaderBuilder(2, proposerKeyPair, emptyList(), parentHeader).buildHeader();
+
+    final BlockHeaderValidator<IbftContext> validator =
+        IbftBlockHeaderValidationRulesetFactory.ibftBlockHeaderValidator(5);
+
+    assertThat(
+            validator.validateHeader(
+                blockHeader, parentHeader, protocolContext(validators), HeaderValidationMode.FULL))
+        .isFalse();
+  }
+
+  @Test
+  public void ibftValidateHeaderFailsOnCoinbaseData() {
+    final KeyPair proposerKeyPair = KeyPair.generate();
+    final Address proposerAddress = Util.publicKeyToAddress(proposerKeyPair.getPublicKey());
+
+    final Address nonProposerAddress = Util.publicKeyToAddress(KeyPair.generate().getPublicKey());
+
+    final List<Address> validators = singletonList(proposerAddress);
+
+    final BlockHeader parentHeader =
+        getPresetHeaderBuilder(1, proposerKeyPair, validators, null).buildHeader();
+    final BlockHeader blockHeader =
+        getPresetHeaderBuilder(2, proposerKeyPair, validators, parentHeader)
+            .coinbase(nonProposerAddress)
+            .buildHeader();
+
+    final BlockHeaderValidator<IbftContext> validator =
+        IbftBlockHeaderValidationRulesetFactory.ibftBlockHeaderValidator(5);
+
+    assertThat(
+            validator.validateHeader(
+                blockHeader, parentHeader, protocolContext(validators), HeaderValidationMode.FULL))
+        .isFalse();
+  }
+
+  @Test
+  public void ibftValidateHeaderFailsOnNonce() {
+    final KeyPair proposerKeyPair = KeyPair.generate();
+    final Address proposerAddress = Util.publicKeyToAddress(proposerKeyPair.getPublicKey());
+
+    final List<Address> validators = singletonList(proposerAddress);
+
+    final BlockHeader parentHeader =
+        getPresetHeaderBuilder(1, proposerKeyPair, validators, null).buildHeader();
+    final BlockHeader blockHeader =
+        getPresetHeaderBuilder(2, proposerKeyPair, validators, parentHeader).nonce(3).buildHeader();
+
+    final BlockHeaderValidator<IbftContext> validator =
+        IbftBlockHeaderValidationRulesetFactory.ibftBlockHeaderValidator(5);
+
+    assertThat(
+            validator.validateHeader(
+                blockHeader, parentHeader, protocolContext(validators), HeaderValidationMode.FULL))
+        .isFalse();
+  }
+
+  @Test
+  public void ibftValidateHeaderFailsOnTimestamp() {
+    final KeyPair proposerKeyPair = KeyPair.generate();
+    final Address proposerAddress = Util.publicKeyToAddress(proposerKeyPair.getPublicKey());
+
+    final List<Address> validators = singletonList(proposerAddress);
+
+    final BlockHeader parentHeader =
+        getPresetHeaderBuilder(1, proposerKeyPair, validators, null).buildHeader();
+    final BlockHeader blockHeader =
+        getPresetHeaderBuilder(2, proposerKeyPair, validators, parentHeader)
+            .timestamp(100)
+            .buildHeader();
+
+    final BlockHeaderValidator<IbftContext> validator =
+        IbftBlockHeaderValidationRulesetFactory.ibftBlockHeaderValidator(5);
+
+    assertThat(
+            validator.validateHeader(
+                blockHeader, parentHeader, protocolContext(validators), HeaderValidationMode.FULL))
+        .isFalse();
+  }
+
+  @Test
+  public void ibftValidateHeaderFailsOnMixHash() {
+    final KeyPair proposerKeyPair = KeyPair.generate();
+    final Address proposerAddress = Util.publicKeyToAddress(proposerKeyPair.getPublicKey());
+
+    final List<Address> validators = singletonList(proposerAddress);
+
+    final BlockHeader parentHeader =
+        getPresetHeaderBuilder(1, proposerKeyPair, validators, null).buildHeader();
+    final BlockHeader blockHeader =
+        getPresetHeaderBuilder(2, proposerKeyPair, validators, parentHeader)
+            .mixHash(Hash.EMPTY_TRIE_HASH)
+            .buildHeader();
+
+    final BlockHeaderValidator<IbftContext> validator =
+        IbftBlockHeaderValidationRulesetFactory.ibftBlockHeaderValidator(5);
+
+    assertThat(
+            validator.validateHeader(
+                blockHeader, parentHeader, protocolContext(validators), HeaderValidationMode.FULL))
+        .isFalse();
+  }
+
+  @Test
+  public void ibftValidateHeaderFailsOnOmmers() {
+    final KeyPair proposerKeyPair = KeyPair.generate();
+    final Address proposerAddress = Util.publicKeyToAddress(proposerKeyPair.getPublicKey());
+
+    final List<Address> validators = singletonList(proposerAddress);
+
+    final BlockHeader parentHeader =
+        getPresetHeaderBuilder(1, proposerKeyPair, validators, null).buildHeader();
+    final BlockHeader blockHeader =
+        getPresetHeaderBuilder(2, proposerKeyPair, validators, parentHeader)
+            .ommersHash(Hash.EMPTY_TRIE_HASH)
+            .buildHeader();
+
+    final BlockHeaderValidator<IbftContext> validator =
+        IbftBlockHeaderValidationRulesetFactory.ibftBlockHeaderValidator(5);
+
+    assertThat(
+            validator.validateHeader(
+                blockHeader, parentHeader, protocolContext(validators), HeaderValidationMode.FULL))
+        .isFalse();
+  }
+
+  @Test
+  public void ibftValidateHeaderFailsOnDifficulty() {
+    final KeyPair proposerKeyPair = KeyPair.generate();
+    final Address proposerAddress = Util.publicKeyToAddress(proposerKeyPair.getPublicKey());
+
+    final List<Address> validators = singletonList(proposerAddress);
+
+    final BlockHeader parentHeader =
+        getPresetHeaderBuilder(1, proposerKeyPair, validators, null).buildHeader();
+    final BlockHeader blockHeader =
+        getPresetHeaderBuilder(2, proposerKeyPair, validators, parentHeader)
+            .difficulty(UInt256.of(5))
+            .buildHeader();
+
+    final BlockHeaderValidator<IbftContext> validator =
+        IbftBlockHeaderValidationRulesetFactory.ibftBlockHeaderValidator(5);
+
+    assertThat(
+            validator.validateHeader(
+                blockHeader, parentHeader, protocolContext(validators), HeaderValidationMode.FULL))
+        .isFalse();
+  }
+
+  @Test
+  public void ibftValidateHeaderFailsOnAncestor() {
+    final KeyPair proposerKeyPair = KeyPair.generate();
+    final Address proposerAddress = Util.publicKeyToAddress(proposerKeyPair.getPublicKey());
+
+    final List<Address> validators = singletonList(proposerAddress);
+
+    final BlockHeader parentHeader =
+        getPresetHeaderBuilder(1, proposerKeyPair, validators, null).buildHeader();
+    final BlockHeader blockHeader =
+        getPresetHeaderBuilder(2, proposerKeyPair, validators, null).buildHeader();
+
+    final BlockHeaderValidator<IbftContext> validator =
+        IbftBlockHeaderValidationRulesetFactory.ibftBlockHeaderValidator(5);
+
+    assertThat(
+            validator.validateHeader(
+                blockHeader, parentHeader, protocolContext(validators), HeaderValidationMode.FULL))
+        .isFalse();
+  }
+
+  @Test
+  public void ibftValidateHeaderFailsOnGasUsage() {
+    final KeyPair proposerKeyPair = KeyPair.generate();
+    final Address proposerAddress = Util.publicKeyToAddress(proposerKeyPair.getPublicKey());
+
+    final List<Address> validators = singletonList(proposerAddress);
+
+    final BlockHeader parentHeader =
+        getPresetHeaderBuilder(1, proposerKeyPair, validators, null).buildHeader();
+    final BlockHeader blockHeader =
+        getPresetHeaderBuilder(2, proposerKeyPair, validators, parentHeader)
+            .gasLimit(5_000)
+            .gasUsed(6_000)
+            .buildHeader();
+
+    final BlockHeaderValidator<IbftContext> validator =
+        IbftBlockHeaderValidationRulesetFactory.ibftBlockHeaderValidator(5);
+
+    assertThat(
+            validator.validateHeader(
+                blockHeader, parentHeader, protocolContext(validators), HeaderValidationMode.FULL))
+        .isFalse();
+  }
+
+  @Test
+  public void ibftValidateHeaderFailsOnGasLimitRange() {
+    final KeyPair proposerKeyPair = KeyPair.generate();
+    final Address proposerAddress = Util.publicKeyToAddress(proposerKeyPair.getPublicKey());
+
+    final List<Address> validators = singletonList(proposerAddress);
+
+    final BlockHeader parentHeader =
+        getPresetHeaderBuilder(1, proposerKeyPair, validators, null).buildHeader();
+    final BlockHeader blockHeader =
+        getPresetHeaderBuilder(2, proposerKeyPair, validators, parentHeader)
+            .gasLimit(4999)
+            .buildHeader();
+
+    final BlockHeaderValidator<IbftContext> validator =
+        IbftBlockHeaderValidationRulesetFactory.ibftBlockHeaderValidator(5);
+
+    assertThat(
+            validator.validateHeader(
+                blockHeader, parentHeader, protocolContext(validators), HeaderValidationMode.FULL))
+        .isFalse();
+  }
+
+  private BlockHeaderTestFixture getPresetHeaderBuilder(
+      final long number,
+      final KeyPair proposerKeyPair,
+      final List<Address> validators,
+      final BlockHeader parent) {
+    final BlockHeaderTestFixture builder = new BlockHeaderTestFixture();
+
+    if (parent != null) {
+      builder.parentHash(parent.getHash());
+    }
+    builder.number(number);
+    builder.gasLimit(5000);
+    builder.timestamp(6000 * number);
+    builder.mixHash(
+        Hash.fromHexString("0x63746963616c2062797a616e74696e65206661756c7420746f6c6572616e6365"));
+    builder.ommersHash(Hash.EMPTY_LIST_HASH);
+    builder.nonce(0);
+    builder.difficulty(UInt256.ONE);
+    builder.coinbase(Util.publicKeyToAddress(proposerKeyPair.getPublicKey()));
+
+    final IbftExtraData ibftExtraData =
+        IbftExtraDataFixture.createExtraData(
+            builder.buildHeader(),
+            BytesValue.wrap(new byte[IbftExtraData.EXTRA_VANITY_LENGTH]),
+            Optional.of(Vote.authVote(Address.fromHexString("1"))),
+            validators,
+            singletonList(proposerKeyPair),
+            0xDEADBEEF);
+
+    builder.extraData(ibftExtraData.encode());
+    return builder;
+  }
+}
--- a/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/IbftExtraDataFixture.java
+++ b/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/IbftExtraDataFixture.java
@ -0,0 +1,100 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.ibft;
+
+import static java.util.Collections.emptyList;
+
+import tech.pegasys.pantheon.crypto.SECP256K1;
+import tech.pegasys.pantheon.crypto.SECP256K1.KeyPair;
+import tech.pegasys.pantheon.crypto.SECP256K1.Signature;
+import tech.pegasys.pantheon.ethereum.core.Address;
+import tech.pegasys.pantheon.ethereum.core.BlockHeader;
+import tech.pegasys.pantheon.ethereum.core.Hash;
+import tech.pegasys.pantheon.util.bytes.BytesValue;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+public class IbftExtraDataFixture {
+
+  public static IbftExtraData createExtraData(
+      final BlockHeader header,
+      final BytesValue vanityData,
+      final Optional<Vote> vote,
+      final List<Address> validators,
+      final List<KeyPair> committerKeyPairs) {
+
+    return createExtraData(header, vanityData, vote, validators, committerKeyPairs, 0);
+  }
+
+  public static IbftExtraData createExtraData(
+      final BlockHeader header,
+      final BytesValue vanityData,
+      final Optional<Vote> vote,
+      final List<Address> validators,
+      final List<KeyPair> committerKeyPairs,
+      final int roundNumber) {
+
+    return createExtraData(
+        header, vanityData, vote, validators, committerKeyPairs, roundNumber, false);
+  }
+
+  public static IbftExtraData createExtraData(
+      final BlockHeader header,
+      final BytesValue vanityData,
+      final Optional<Vote> vote,
+      final List<Address> validators,
+      final List<KeyPair> committerKeyPairs,
+      final int baseRoundNumber,
+      final boolean useDifferentRoundNumbersForCommittedSeals) {
+
+    final IbftExtraData ibftExtraDataNoCommittedSeals =
+        new IbftExtraData(vanityData, emptyList(), vote, baseRoundNumber, validators);
+
+    // if useDifferentRoundNumbersForCommittedSeals is true then each committed seal will be
+    // calculated for an extraData field with a different round number
+    List<Signature> commitSeals =
+        IntStream.range(0, committerKeyPairs.size())
+            .mapToObj(
+                i -> {
+                  final int round =
+                      useDifferentRoundNumbersForCommittedSeals
+                          ? ibftExtraDataNoCommittedSeals.getRound() + i
+                          : ibftExtraDataNoCommittedSeals.getRound();
+
+                  IbftExtraData extraDataForCommittedSealCalculation =
+                      new IbftExtraData(
+                          ibftExtraDataNoCommittedSeals.getVanityData(),
+                          emptyList(),
+                          ibftExtraDataNoCommittedSeals.getVote(),
+                          round,
+                          ibftExtraDataNoCommittedSeals.getValidators());
+
+                  final Hash headerHashForCommitters =
+                      IbftBlockHashing.calculateDataHashForCommittedSeal(
+                          header, extraDataForCommittedSealCalculation);
+
+                  return SECP256K1.sign(headerHashForCommitters, committerKeyPairs.get(i));
+                })
+            .collect(Collectors.toList());
+
+    return new IbftExtraData(
+        ibftExtraDataNoCommittedSeals.getVanityData(),
+        commitSeals,
+        ibftExtraDataNoCommittedSeals.getVote(),
+        ibftExtraDataNoCommittedSeals.getRound(),
+        ibftExtraDataNoCommittedSeals.getValidators());
+  }
+}
--- a/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/Ibft2ExtraDataTest.java
+++ b/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/Ibft2ExtraDataTest.java
@ -31,7 +31,7 @@ import java.util.Random;
 import com.google.common.collect.Lists;
 import org.junit.Test;

-public class Ibft2ExtraDataTest {
+public class IbftExtraDataTest {
  private final String RAW_HEX_ENCODING_STRING =
      "f8f1a00102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f20ea9400000000000000000000000000000000000"
          + "00001940000000000000000000000000000000000000002d794000000000000000000000000000000000000000181ff8400fedc"
@ -39,10 +39,10 @@ public class Ibft2ExtraDataTest {
          + "0000000000000000000000000000000000a00b84100000000000000000000000000000000000000000000000000000000000000"
          + "0a000000000000000000000000000000000000000000000000000000000000000100";

-  private final Ibft2ExtraData DECODED_EXTRA_DATA_FOR_RAW_HEX_ENCODING_STRING =
+  private final IbftExtraData DECODED_EXTRA_DATA_FOR_RAW_HEX_ENCODING_STRING =
      getDecodedExtraDataForRawHexEncodingString();

-  private static Ibft2ExtraData getDecodedExtraDataForRawHexEncodingString() {
+  private static IbftExtraData getDecodedExtraDataForRawHexEncodingString() {
    final List<Address> validators =
        Arrays.asList(Address.fromHexString("1"), Address.fromHexString("2"));
    final Optional<Vote> vote = Optional.of(Vote.authVote(Address.fromHexString("1")));
@ -56,7 +56,7 @@ public class Ibft2ExtraDataTest {
    final byte[] vanity_bytes = createNonEmptyVanityData();
    final BytesValue vanity_data = BytesValue.wrap(vanity_bytes);

-    return new Ibft2ExtraData(vanity_data, committerSeals, vote, round, validators);
+    return new IbftExtraData(vanity_data, committerSeals, vote, round, validators);
  }

  @Test
@ -90,7 +90,7 @@ public class Ibft2ExtraDataTest {

    final BytesValue bufferToInject = encoder.encoded();

-    final Ibft2ExtraData extraData = Ibft2ExtraData.decode(bufferToInject);
+    final IbftExtraData extraData = IbftExtraData.decode(bufferToInject);

    assertThat(extraData.getVanityData()).isEqualTo(vanity_data);
    assertThat(extraData.getVote()).isEqualTo(vote);
@ -100,7 +100,7 @@ public class Ibft2ExtraDataTest {
  }

  /**
-   * This test specifically verifies that {@link Ibft2ExtraData#decode(BytesValue)} uses {@link
+   * This test specifically verifies that {@link IbftExtraData#decode(BytesValue)} uses {@link
   * RLPInput#readInt()} rather than {@link RLPInput#readIntScalar()} to decode the round number
   */
  @Test
@ -134,8 +134,7 @@ public class Ibft2ExtraDataTest {

    final BytesValue bufferToInject = encoder.encoded();

-    assertThatThrownBy(() -> Ibft2ExtraData.decode(bufferToInject))
-        .isInstanceOf(RLPException.class);
+    assertThatThrownBy(() -> IbftExtraData.decode(bufferToInject)).isInstanceOf(RLPException.class);
  }

  @Test
@ -163,7 +162,7 @@ public class Ibft2ExtraDataTest {

    final BytesValue bufferToInject = encoder.encoded();

-    final Ibft2ExtraData extraData = Ibft2ExtraData.decode(bufferToInject);
+    final IbftExtraData extraData = IbftExtraData.decode(bufferToInject);

    assertThat(extraData.getVanityData()).isEqualTo(vanity_data);
    assertThat(extraData.getVote().isPresent()).isEqualTo(false);
@ -183,10 +182,10 @@ public class Ibft2ExtraDataTest {
    final byte[] vanity_bytes = new byte[32];
    final BytesValue vanity_data = BytesValue.wrap(vanity_bytes);

-    final Ibft2ExtraData expectedExtraData =
-        new Ibft2ExtraData(vanity_data, committerSeals, vote, round, validators);
+    IbftExtraData expectedExtraData =
+        new IbftExtraData(vanity_data, committerSeals, vote, round, validators);

-    final Ibft2ExtraData actualExtraData = Ibft2ExtraData.decode(expectedExtraData.encode());
+    IbftExtraData actualExtraData = IbftExtraData.decode(expectedExtraData.encode());

    assertThat(actualExtraData).isEqualToComparingFieldByField(expectedExtraData);
  }
@ -220,7 +219,7 @@ public class Ibft2ExtraDataTest {

    final BytesValue bufferToInject = encoder.encoded();

-    final Ibft2ExtraData extraData = Ibft2ExtraData.decode(bufferToInject);
+    final IbftExtraData extraData = IbftExtraData.decode(bufferToInject);

    assertThat(extraData.getVanityData()).isEqualTo(vanity_data);
    assertThat(extraData.getVote()).isEqualTo(vote);
@ -240,10 +239,10 @@ public class Ibft2ExtraDataTest {
    final byte[] vanity_bytes = new byte[32];
    final BytesValue vanity_data = BytesValue.wrap(vanity_bytes);

-    final Ibft2ExtraData expectedExtraData =
-        new Ibft2ExtraData(vanity_data, committerSeals, vote, round, validators);
+    IbftExtraData expectedExtraData =
+        new IbftExtraData(vanity_data, committerSeals, vote, round, validators);

-    final Ibft2ExtraData actualExtraData = Ibft2ExtraData.decode(expectedExtraData.encode());
+    IbftExtraData actualExtraData = IbftExtraData.decode(expectedExtraData.encode());

    assertThat(actualExtraData).isEqualToComparingFieldByField(expectedExtraData);
  }
@ -282,7 +281,7 @@ public class Ibft2ExtraDataTest {

    final BytesValue bufferToInject = encoder.encoded();

-    final Ibft2ExtraData extraData = Ibft2ExtraData.decode(bufferToInject);
+    final IbftExtraData extraData = IbftExtraData.decode(bufferToInject);

    assertThat(extraData.getVanityData()).isEqualTo(vanity_data);
    assertThat(extraData.getVote()).isEqualTo(vote);
@ -306,10 +305,10 @@ public class Ibft2ExtraDataTest {
    final byte[] vanity_bytes = createNonEmptyVanityData();
    final BytesValue vanity_data = BytesValue.wrap(vanity_bytes);

-    final Ibft2ExtraData expectedExtraData =
-        new Ibft2ExtraData(vanity_data, committerSeals, vote, round, validators);
+    IbftExtraData expectedExtraData =
+        new IbftExtraData(vanity_data, committerSeals, vote, round, validators);

-    final Ibft2ExtraData actualExtraData = Ibft2ExtraData.decode(expectedExtraData.encode());
+    IbftExtraData actualExtraData = IbftExtraData.decode(expectedExtraData.encode());

    assertThat(actualExtraData).isEqualToComparingFieldByField(expectedExtraData);
  }
@ -324,14 +323,87 @@ public class Ibft2ExtraDataTest {
  @Test
  public void decodingOfKnownRawHexStringMatchesKnowExtraDataObject() {

-    final Ibft2ExtraData expectedExtraData = DECODED_EXTRA_DATA_FOR_RAW_HEX_ENCODING_STRING;
+    final IbftExtraData expectedExtraData = DECODED_EXTRA_DATA_FOR_RAW_HEX_ENCODING_STRING;

-    final BytesValue rawDecoding = BytesValue.fromHexString(RAW_HEX_ENCODING_STRING);
-    final Ibft2ExtraData actualExtraData = Ibft2ExtraData.decode(rawDecoding);
+    BytesValue rawDecoding = BytesValue.fromHexString(RAW_HEX_ENCODING_STRING);
+    IbftExtraData actualExtraData = IbftExtraData.decode(rawDecoding);

    assertThat(actualExtraData).isEqualToComparingFieldByField(expectedExtraData);
  }

+  @Test
+  public void testEncodeWithoutCommitSeals() {
+    final List<Address> validators =
+        Arrays.asList(Address.fromHexString("1"), Address.fromHexString("2"));
+    final Optional<Vote> vote = Optional.of(Vote.authVote(Address.fromHexString("1")));
+    final int round = 0x00FEDCBA;
+    final List<Signature> committerSeals =
+        Arrays.asList(
+            Signature.create(BigInteger.ONE, BigInteger.TEN, (byte) 0),
+            Signature.create(BigInteger.TEN, BigInteger.ONE, (byte) 0));
+
+    // Create a byte buffer with no data.
+    final byte[] vanity_bytes = createNonEmptyVanityData();
+    final BytesValue vanity_data = BytesValue.wrap(vanity_bytes);
+
+    final BytesValueRLPOutput encoder = new BytesValueRLPOutput();
+    encoder.startList();
+    encoder.writeBytesValue(vanity_data);
+    encoder.writeList(validators, (validator, rlp) -> rlp.writeBytesValue(validator));
+
+    // encoded vote
+    encoder.startList();
+    encoder.writeBytesValue(vote.get().getRecipient());
+    vote.get().getVoteType().writeTo(encoder);
+    encoder.endList();
+    encoder.writeInt(round);
+    encoder.endList();
+
+    BytesValue expectedEncoding = encoder.encoded();
+
+    BytesValue actualEncoding =
+        new IbftExtraData(vanity_data, committerSeals, vote, round, validators)
+            .encodeWithoutCommitSeals();
+
+    assertThat(actualEncoding).isEqualTo(expectedEncoding);
+  }
+
+  @Test
+  public void testEncodeWithoutCommitSealsAndRoundNumber() {
+    final List<Address> validators =
+        Arrays.asList(Address.fromHexString("1"), Address.fromHexString("2"));
+    final Optional<Vote> vote = Optional.of(Vote.authVote(Address.fromHexString("1")));
+    final int round = 0x00FEDCBA;
+    final List<Signature> committerSeals =
+        Arrays.asList(
+            Signature.create(BigInteger.ONE, BigInteger.TEN, (byte) 0),
+            Signature.create(BigInteger.TEN, BigInteger.ONE, (byte) 0));
+
+    // Create a byte buffer with no data.
+    final byte[] vanity_bytes = createNonEmptyVanityData();
+    final BytesValue vanity_data = BytesValue.wrap(vanity_bytes);
+
+    final BytesValueRLPOutput encoder = new BytesValueRLPOutput();
+    encoder.startList();
+    encoder.writeBytesValue(vanity_data);
+    encoder.writeList(validators, (validator, rlp) -> rlp.writeBytesValue(validator));
+
+    // encoded vote
+    encoder.startList();
+    encoder.writeBytesValue(vote.get().getRecipient());
+    vote.get().getVoteType().writeTo(encoder);
+    encoder.endList();
+    encoder.endList();
+
+    BytesValue expectedEncoding = encoder.encoded();
+
+    BytesValue actualEncoding =
+        new IbftExtraData(vanity_data, committerSeals, vote, round, validators)
+            .encodeWithoutCommitSealsAndRoundNumber();
+
+    assertThat(actualEncoding).isEqualTo(expectedEncoding);
+  }
+
  @Test
  public void incorrectlyStructuredRlpThrowsException() {
    final List<Address> validators = Lists.newArrayList();
@ -362,8 +434,7 @@ public class Ibft2ExtraDataTest {

    final BytesValue bufferToInject = encoder.encoded();

-    assertThatThrownBy(() -> Ibft2ExtraData.decode(bufferToInject))
-        .isInstanceOf(RLPException.class);
+    assertThatThrownBy(() -> IbftExtraData.decode(bufferToInject)).isInstanceOf(RLPException.class);
  }

  @Test
@ -400,8 +471,7 @@ public class Ibft2ExtraDataTest {

    final BytesValue bufferToInject = encoder.encoded();

-    assertThatThrownBy(() -> Ibft2ExtraData.decode(bufferToInject))
-        .isInstanceOf(RLPException.class);
+    assertThatThrownBy(() -> IbftExtraData.decode(bufferToInject)).isInstanceOf(RLPException.class);
  }

  private static byte[] createNonEmptyVanityData() {
@ -409,7 +479,6 @@ public class Ibft2ExtraDataTest {
    for (int i = 0; i < vanity_bytes.length; i++) {
      vanity_bytes[i] = (byte) (i + 1);
    }
-
    return vanity_bytes;
  }
 }
--- a/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/IbftVoteTypeTest.java
+++ b/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/IbftVoteTypeTest.java
@ -0,0 +1,29 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.ibft;
+
+import static org.assertj.core.api.Java6Assertions.assertThat;
+
+import org.junit.Test;
+
+public class IbftVoteTypeTest {
+
+  @Test
+  public void testValidatorVoteMethodImplementation() {
+    assertThat(IbftVoteType.ADD.isAddVote()).isTrue();
+    assertThat(IbftVoteType.ADD.isDropVote()).isFalse();
+
+    assertThat(IbftVoteType.DROP.isAddVote()).isFalse();
+    assertThat(IbftVoteType.DROP.isDropVote()).isTrue();
+  }
+}
--- a/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/headervalidationrules/IbftCoinbaseValidationRuleTest.java
+++ b/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/headervalidationrules/IbftCoinbaseValidationRuleTest.java
@ -0,0 +1,104 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.ibft.headervalidationrules;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import tech.pegasys.pantheon.consensus.common.VoteTally;
+import tech.pegasys.pantheon.consensus.ibft.IbftContext;
+import tech.pegasys.pantheon.consensus.ibft.IbftExtraData;
+import tech.pegasys.pantheon.consensus.ibft.IbftExtraDataFixture;
+import tech.pegasys.pantheon.consensus.ibft.Vote;
+import tech.pegasys.pantheon.crypto.SECP256K1.KeyPair;
+import tech.pegasys.pantheon.ethereum.ProtocolContext;
+import tech.pegasys.pantheon.ethereum.core.Address;
+import tech.pegasys.pantheon.ethereum.core.BlockHeader;
+import tech.pegasys.pantheon.ethereum.core.BlockHeaderTestFixture;
+import tech.pegasys.pantheon.ethereum.core.Hash;
+import tech.pegasys.pantheon.ethereum.core.Util;
+import tech.pegasys.pantheon.util.bytes.BytesValue;
+
+import java.util.List;
+import java.util.Optional;
+
+import com.google.common.collect.Lists;
+import org.junit.Test;
+
+public class IbftCoinbaseValidationRuleTest {
+
+  public static BlockHeader createProposedBlockHeader(
+      final KeyPair proposerKeyPair,
+      final List<Address> validators,
+      final List<KeyPair> committerKeyPairs) {
+
+    final BlockHeaderTestFixture builder = new BlockHeaderTestFixture();
+    builder.number(1); // must NOT be block 0, as that should not contain seals at all
+    builder.coinbase(Util.publicKeyToAddress(proposerKeyPair.getPublicKey()));
+    final BlockHeader header = builder.buildHeader();
+
+    final IbftExtraData ibftExtraData =
+        IbftExtraDataFixture.createExtraData(
+            header,
+            BytesValue.wrap(new byte[IbftExtraData.EXTRA_VANITY_LENGTH]),
+            Optional.of(Vote.authVote(Address.fromHexString("1"))),
+            validators,
+            committerKeyPairs);
+
+    builder.extraData(ibftExtraData.encode());
+    return builder.buildHeader();
+  }
+
+  @Test
+  public void proposerInValidatorListPassesValidation() {
+    final KeyPair proposerKeyPair = KeyPair.generate();
+    final Address proposerAddress =
+        Address.extract(Hash.hash(proposerKeyPair.getPublicKey().getEncodedBytes()));
+
+    final List<Address> validators = Lists.newArrayList(proposerAddress);
+
+    final List<KeyPair> committers = Lists.newArrayList(proposerKeyPair);
+
+    final VoteTally voteTally = new VoteTally(validators);
+    final ProtocolContext<IbftContext> context =
+        new ProtocolContext<>(null, null, new IbftContext(voteTally, null));
+
+    final IbftCoinbaseValidationRule coinbaseValidationRule = new IbftCoinbaseValidationRule();
+
+    BlockHeader header = createProposedBlockHeader(proposerKeyPair, validators, committers);
+
+    assertThat(coinbaseValidationRule.validate(header, null, context)).isTrue();
+  }
+
+  @Test
+  public void proposerNotInValidatorListFailsValidation() {
+    final KeyPair proposerKeyPair = KeyPair.generate();
+
+    final KeyPair otherValidatorKeyPair = KeyPair.generate();
+    final Address otherValidatorNodeAddress =
+        Address.extract(Hash.hash(otherValidatorKeyPair.getPublicKey().getEncodedBytes()));
+
+    final List<Address> validators = Lists.newArrayList(otherValidatorNodeAddress);
+
+    final List<KeyPair> committers = Lists.newArrayList(otherValidatorKeyPair);
+
+    final VoteTally voteTally = new VoteTally(validators);
+    final ProtocolContext<IbftContext> context =
+        new ProtocolContext<>(null, null, new IbftContext(voteTally, null));
+
+    final IbftCoinbaseValidationRule coinbaseValidationRule = new IbftCoinbaseValidationRule();
+
+    BlockHeader header = createProposedBlockHeader(proposerKeyPair, validators, committers);
+
+    assertThat(coinbaseValidationRule.validate(header, null, context)).isFalse();
+  }
+}
--- a/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/headervalidationrules/IbftExtraDataValidationRuleTest.java
+++ b/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/headervalidationrules/IbftExtraDataValidationRuleTest.java
@ -0,0 +1,253 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.consensus.ibft.headervalidationrules;
+
+import static java.util.Collections.emptyList;
+import static java.util.Collections.singletonList;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import tech.pegasys.pantheon.consensus.common.VoteTally;
+import tech.pegasys.pantheon.consensus.ibft.IbftContext;
+import tech.pegasys.pantheon.consensus.ibft.IbftExtraData;
+import tech.pegasys.pantheon.consensus.ibft.IbftExtraDataFixture;
+import tech.pegasys.pantheon.consensus.ibft.Vote;
+import tech.pegasys.pantheon.crypto.SECP256K1.KeyPair;
+import tech.pegasys.pantheon.ethereum.ProtocolContext;
+import tech.pegasys.pantheon.ethereum.core.Address;
+import tech.pegasys.pantheon.ethereum.core.BlockHeader;
+import tech.pegasys.pantheon.ethereum.core.BlockHeaderTestFixture;
+import tech.pegasys.pantheon.ethereum.core.Hash;
+import tech.pegasys.pantheon.ethereum.core.Util;
+import tech.pegasys.pantheon.util.bytes.BytesValue;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+import com.google.common.collect.Lists;
+import org.junit.Test;
+
+public class IbftExtraDataValidationRuleTest {
+
+  public static BlockHeader createProposedBlockHeader(
+      final List<Address> validators,
+      final List<KeyPair> committerKeyPairs,
+      final boolean useDifferentRoundNumbersForCommittedSeals) {
+    final int BASE_ROUND_NUMBER = 5;
+    final BlockHeaderTestFixture builder = new BlockHeaderTestFixture();
+    builder.number(1); // must NOT be block 0, as that should not contain seals at all
+
+    final BlockHeader header = builder.buildHeader();
+
+    final IbftExtraData ibftExtraData =
+        IbftExtraDataFixture.createExtraData(
+            header,
+            BytesValue.wrap(new byte[IbftExtraData.EXTRA_VANITY_LENGTH]),
+            Optional.of(Vote.authVote(Address.fromHexString("1"))),
+            validators,
+            committerKeyPairs,
+            BASE_ROUND_NUMBER,
+            useDifferentRoundNumbersForCommittedSeals);
+
+    builder.extraData(ibftExtraData.encode());
+    return builder.buildHeader();
+  }
+
+  @Test
+  public void correctlyConstructedHeaderPassesValidation() {
+    final List<KeyPair> committerKeyPairs =
+        IntStream.range(0, 2).mapToObj(i -> KeyPair.generate()).collect(Collectors.toList());
+
+    final List<Address> committerAddresses =
+        committerKeyPairs
+            .stream()
+            .map(keyPair -> Util.publicKeyToAddress(keyPair.getPublicKey()))
+            .sorted()
+            .collect(Collectors.toList());
+
+    final VoteTally voteTally = new VoteTally(committerAddresses);
+    final ProtocolContext<IbftContext> context =
+        new ProtocolContext<>(null, null, new IbftContext(voteTally, null));
+
+    final IbftExtraDataValidationRule extraDataValidationRule =
+        new IbftExtraDataValidationRule(true);
+
+    BlockHeader header = createProposedBlockHeader(committerAddresses, committerKeyPairs, false);
+
+    assertThat(extraDataValidationRule.validate(header, null, context)).isTrue();
+  }
+
+  @Test
+  public void insufficientCommitSealsFailsValidation() {
+    final KeyPair committerKeyPair = KeyPair.generate();
+    final Address committerAddress =
+        Address.extract(Hash.hash(committerKeyPair.getPublicKey().getEncodedBytes()));
+
+    final List<Address> validators = singletonList(committerAddress);
+    final VoteTally voteTally = new VoteTally(validators);
+    final ProtocolContext<IbftContext> context =
+        new ProtocolContext<>(null, null, new IbftContext(voteTally, null));
+
+    final IbftExtraDataValidationRule extraDataValidationRule =
+        new IbftExtraDataValidationRule(true);
+
+    final BlockHeader header = createProposedBlockHeader(validators, emptyList(), false);
+
+    // Note that no committer seals are in the header's IBFT extra data.
+    final IbftExtraData headerExtraData = IbftExtraData.decode(header.getExtraData());
+    assertThat(headerExtraData.getSeals().size()).isEqualTo(0);
+
+    assertThat(extraDataValidationRule.validate(header, null, context)).isFalse();
+  }
+
+  @Test
+  public void outOfOrderValidatorListFailsValidation() {
+    final List<KeyPair> committerKeyPairs =
+        IntStream.range(0, 2).mapToObj(i -> KeyPair.generate()).collect(Collectors.toList());
+
+    final List<Address> committerAddresses =
+        committerKeyPairs
+            .stream()
+            .map(keyPair -> Util.publicKeyToAddress(keyPair.getPublicKey()))
+            .sorted()
+            .collect(Collectors.toList());
+
+    final List<Address> validators = Lists.reverse(committerAddresses);
+
+    final VoteTally voteTally = new VoteTally(validators);
+    final ProtocolContext<IbftContext> context =
+        new ProtocolContext<>(null, null, new IbftContext(voteTally, null));
+
+    final IbftExtraDataValidationRule extraDataValidationRule =
+        new IbftExtraDataValidationRule(true);
+
+    BlockHeader header = createProposedBlockHeader(validators, committerKeyPairs, false);
+
+    assertThat(extraDataValidationRule.validate(header, null, context)).isFalse();
+  }
+
+  @Test
+  public void mismatchingReportedValidatorsVsLocallyStoredListFailsValidation() {
+    final List<KeyPair> committerKeyPairs =
+        IntStream.range(0, 2).mapToObj(i -> KeyPair.generate()).collect(Collectors.toList());
+
+    final List<Address> validators =
+        IntStream.range(0, 2)
+            .mapToObj(i -> Util.publicKeyToAddress(KeyPair.generate().getPublicKey()))
+            .collect(Collectors.toList());
+
+    final VoteTally voteTally = new VoteTally(validators);
+    final ProtocolContext<IbftContext> context =
+        new ProtocolContext<>(null, null, new IbftContext(voteTally, null));
+
+    final IbftExtraDataValidationRule extraDataValidationRule =
+        new IbftExtraDataValidationRule(true);
+
+    BlockHeader header = createProposedBlockHeader(validators, committerKeyPairs, false);
+
+    assertThat(extraDataValidationRule.validate(header, null, context)).isFalse();
+  }
+
+  @Test
+  public void committerNotInValidatorListFailsValidation() {
+    final KeyPair committerKeyPair = KeyPair.generate();
+    final Address committerAddress = Util.publicKeyToAddress(committerKeyPair.getPublicKey());
+
+    final List<Address> validators = singletonList(committerAddress);
+    final VoteTally voteTally = new VoteTally(validators);
+
+    // Insert an extraData block with committer seals.
+    final KeyPair nonValidatorKeyPair = KeyPair.generate();
+
+    BlockHeader header =
+        createProposedBlockHeader(validators, singletonList(nonValidatorKeyPair), false);
+
+    final ProtocolContext<IbftContext> context =
+        new ProtocolContext<>(null, null, new IbftContext(voteTally, null));
+    final IbftExtraDataValidationRule extraDataValidationRule =
+        new IbftExtraDataValidationRule(true);
+
+    assertThat(extraDataValidationRule.validate(header, null, context)).isFalse();
+  }
+
+  @Test
+  public void ratioOfCommittersToValidatorsAffectValidation() {
+    assertThat(subExecution(4, 4, false)).isEqualTo(true);
+    assertThat(subExecution(4, 3, false)).isEqualTo(true);
+    assertThat(subExecution(4, 2, false)).isEqualTo(false);
+
+    assertThat(subExecution(5, 4, false)).isEqualTo(true);
+    assertThat(subExecution(5, 3, false)).isEqualTo(false);
+    assertThat(subExecution(5, 2, false)).isEqualTo(false);
+
+    assertThat(subExecution(6, 4, false)).isEqualTo(true);
+    assertThat(subExecution(6, 3, false)).isEqualTo(false);
+    assertThat(subExecution(6, 2, false)).isEqualTo(false);
+
+    assertThat(subExecution(7, 5, false)).isEqualTo(true);
+    assertThat(subExecution(7, 4, false)).isEqualTo(false);
+
+    assertThat(subExecution(8, 6, false)).isEqualTo(true);
+    assertThat(subExecution(8, 5, false)).isEqualTo(false);
+    assertThat(subExecution(8, 4, false)).isEqualTo(false);
+
+    assertThat(subExecution(9, 6, false)).isEqualTo(true);
+    assertThat(subExecution(9, 5, false)).isEqualTo(false);
+    assertThat(subExecution(9, 4, false)).isEqualTo(false);
+
+    assertThat(subExecution(10, 7, false)).isEqualTo(true);
+    assertThat(subExecution(10, 6, false)).isEqualTo(false);
+
+    assertThat(subExecution(12, 8, false)).isEqualTo(true);
+    assertThat(subExecution(12, 7, false)).isEqualTo(false);
+    assertThat(subExecution(12, 6, false)).isEqualTo(false);
+  }
+
+  @Test
+  public void validationFailsIfCommittedSealsAreForDifferentRounds() {
+    assertThat(subExecution(2, 2, true)).isEqualTo(false);
+    assertThat(subExecution(4, 4, true)).isEqualTo(false);
+  }
+
+  private boolean subExecution(
+      final int validatorCount,
+      final int committerCount,
+      final boolean useDifferentRoundNumbersForCommittedSeals) {
+
+    final List<Address> validators = Lists.newArrayList();
+    final List<KeyPair> committerKeys = Lists.newArrayList();
+
+    for (int i = 0; i < validatorCount; i++) { // need -1 to account for proposer
+      final KeyPair committerKeyPair = KeyPair.generate();
+      committerKeys.add(committerKeyPair);
+      validators.add(Address.extract(Hash.hash(committerKeyPair.getPublicKey().getEncodedBytes())));
+    }
+
+    Collections.sort(validators);
+    final VoteTally voteTally = new VoteTally(validators);
+    BlockHeader header =
+        createProposedBlockHeader(
+            validators,
+            committerKeys.subList(0, committerCount),
+            useDifferentRoundNumbersForCommittedSeals);
+
+    final ProtocolContext<IbftContext> context =
+        new ProtocolContext<>(null, null, new IbftContext(voteTally, null));
+    final IbftExtraDataValidationRule extraDataValidationRule =
+        new IbftExtraDataValidationRule(true);
+
+    return extraDataValidationRule.validate(header, null, context);
+  }
+}
--- a/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/Util.java
+++ b/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/Util.java
@ -34,4 +34,12 @@ public class Util {
  public static Address publicKeyToAddress(final PublicKey publicKey) {
    return Address.extract(Hash.hash(publicKey.getEncodedBytes()));
  }
+
+  /**
+   * Implements a fast version of ceiling(numerator/denominator) that does not require using
+   * floating point math
+   */
+  public static int fastDivCeiling(final int numerator, final int denominator) {
+    return ((numerator - 1) / denominator) + 1;
+  }
 }
--- a/ethereum/core/src/test/java/tech/pegasys/pantheon/ethereum/core/UtilTest.java
+++ b/ethereum/core/src/test/java/tech/pegasys/pantheon/ethereum/core/UtilTest.java
@ -0,0 +1,33 @@
+/*
+ * Copyright 2018 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.ethereum.core;
+
+import static org.assertj.core.api.Java6Assertions.assertThat;
+
+import org.junit.Test;
+
+public class UtilTest {
+  @Test
+  public void testFastDivCeil() {
+    assertThat(Util.fastDivCeiling(0, 3)).isEqualTo(1);
+    assertThat(Util.fastDivCeiling(1, 3)).isEqualTo(1);
+    assertThat(Util.fastDivCeiling(2, 3)).isEqualTo(1);
+    assertThat(Util.fastDivCeiling(3, 3)).isEqualTo(1);
+
+    assertThat(Util.fastDivCeiling(4, 3)).isEqualTo(2);
+    assertThat(Util.fastDivCeiling(5, 3)).isEqualTo(2);
+    assertThat(Util.fastDivCeiling(6, 3)).isEqualTo(2);
+
+    assertThat(Util.fastDivCeiling(7, 3)).isEqualTo(3);
+  }
+}