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An enterprise-grade Java-based, Apache 2.0 licensed Ethereum client https://wiki.hyperledger.org/display/besu
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89 lines
4.4 KiB
89 lines
4.4 KiB
description: Privacy
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# Privacy
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Privacy in Pantheon refers to the ability to keep transactions private between the involved parties.
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Other parties cannot access the transaction content, sending party, or list of participating parties.
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!!! important
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For production systems requiring private transactions, we recommend using a network
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with a consensus mechanism supporting transaction finality. For example, [IBFT 2.0](../Consensus-Protocols/IBFT.md).
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## Private Transaction Manager
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Pantheon uses a Private Transaction Manager to implement privacy. For example, [Orion](http://docs.orion.pegasys.tech).
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Each Pantheon node that sends or receives private transactions requires an associated Orion node.
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Private transactions are passed from the Pantheon node to the associated Orion node. The Orion node
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encrypts and directly distributes (that is, point to point) the private transaction to Orion nodes
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participating in the transaction.
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!!! tip
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Private Transaction Managers are also known as Enclaves.
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## Private Transaction Attributes
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Private transactions have additional attributes to public Ethereum transactions:
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* `privateFrom` - Orion public key of transaction sender
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* `privateFor` - Orion public keys of transaction recipients
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* `restriction` - Private transactions are `restricted` or `unrestricted`:
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- In `restricted` private transactions the payload of the private transaction is received and stored only by
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the nodes participating in the transaction.
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- In `unrestricted` private transactions the payload of the private transaction is transmitted to all nodes
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in the network but is readable only by nodes participating in the transaction.
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!!! important
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Pantheon implements `restricted` private transactions only.
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## Pantheon and Orion Keys
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Pantheon and Orion nodes both have public/private key pairs identifying them. The private transaction
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submitted from the Pantheon node to the Orion node is signed with the Pantheon node private key. The
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`privateFrom` and `privateFor` attributes specified in the RLP-encoded transaction string for
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[`eea_sendRawTransaction`](../Reference/Pantheon-API-Methods.md#eea_sendrawtransaction) are the public keys
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of the Orion nodes sending and receiving the transaction.
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!!! important
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The mapping of Pantheon node addresses to Orion node public keys is off-chain. That is, the
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sender of a private transaction must know the Orion node public key of the recipient.
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## Privacy Groups
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The group of nodes specified by `privateFrom`and `privateFor` form a privacy group and
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are given a unique privacy group ID by Orion. The private transaction is stored in Orion with the privacy group ID.
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The Pantheon nodes maintain the public world state for the blockchain and a private state for each privacy group.
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The private states contain data that is not shared in the globally replicated world state. Private transactions read
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and write to the private world state for the privacy group, and read from the public world state.
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!!! note
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The Orion nodes are not shown above for clarity only. To send private transactions,
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each Pantheon node must have an associated Orion node.
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!!! example
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The above illustrates two privacy groups enabling:
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* A, B, and C to send transactions that are private from D
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* A, C, and D to send transactions that are private from B
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To send private transactions between A, B, and C, A initialises a contract in a private transaction with
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B and C specified as the `privateFor` and A specified as the `privateFrom`. Initialising the contract
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creates a privacy group consisting of A, B, and C. For the ABC private state to remain consistent,
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A, B, and C must be included on transactions (as either `privateFrom` or `privateFor`) even if they are
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between two of the three parties.
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To send private transactions between A, C, and D, C initialises a different contract in a private transaction with
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A and D specified as the `privateFor` and C specified as the `privateFrom`. Initialising the contract
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creates a privacy group consisting of A, C, and D. For the ACD private state to remain consistent,
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A, C, and D must be included on transactions (as either `privateFrom` or `privateFor`) even if they are
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between two of the three parties.
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