Eugene Kim
6 years ago
commit
6421d0a8c0
@ -0,0 +1,226 @@ |
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package bls |
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import ( |
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"errors" |
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"fmt" |
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"github.com/harmony-one/bls/ffi/go/bls" |
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) |
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// AggregateSig aggregates all the BLS signature into a single multi-signature.
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func AggregateSig(sigs []*bls.Sign) *bls.Sign { |
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var aggregatedSig bls.Sign |
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for _, sig := range sigs { |
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aggregatedSig.Add(sig) |
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} |
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return &aggregatedSig |
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} |
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// Mask represents a cosigning participation bitmask.
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type Mask struct { |
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Bitmap []byte |
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publics []*bls.PublicKey |
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AggregatePublic *bls.PublicKey |
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} |
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// NewMask returns a new participation bitmask for cosigning where all
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// cosigners are disabled by default. If a public key is given it verifies that
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// it is present in the list of keys and sets the corresponding index in the
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// bitmask to 1 (enabled).
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func NewMask(publics []*bls.PublicKey, myKey *bls.PublicKey) (*Mask, error) { |
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m := &Mask{ |
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publics: publics, |
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} |
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m.Bitmap = make([]byte, m.Len()) |
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m.AggregatePublic = &bls.PublicKey{} |
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if myKey != nil { |
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found := false |
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for i, key := range publics { |
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if key.IsEqual(myKey) { |
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m.SetBit(i, true) |
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found = true |
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break |
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} |
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} |
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if !found { |
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return nil, errors.New("key not found") |
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} |
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} |
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return m, nil |
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} |
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// Mask returns a copy of the participation bitmask.
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func (m *Mask) Mask() []byte { |
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clone := make([]byte, len(m.Bitmap)) |
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copy(clone[:], m.Bitmap) |
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return clone |
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} |
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// Len returns the Bitmap length in bytes.
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func (m *Mask) Len() int { |
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return (len(m.publics) + 7) >> 3 |
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} |
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// SetMask sets the participation bitmask according to the given byte slice
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// interpreted in little-endian order, i.e., bits 0-7 of byte 0 correspond to
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// cosigners 0-7, bits 0-7 of byte 1 correspond to cosigners 8-15, etc.
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func (m *Mask) SetMask(mask []byte) error { |
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if m.Len() != len(mask) { |
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return fmt.Errorf("mismatching Bitmap lengths") |
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} |
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for i := range m.publics { |
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byt := i >> 3 |
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msk := byte(1) << uint(i&7) |
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if ((m.Bitmap[byt] & msk) == 0) && ((mask[byt] & msk) != 0) { |
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m.Bitmap[byt] ^= msk // flip bit in Bitmap from 0 to 1
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m.AggregatePublic.Add(m.publics[i]) |
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} |
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if ((m.Bitmap[byt] & msk) != 0) && ((mask[byt] & msk) == 0) { |
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m.Bitmap[byt] ^= msk // flip bit in Bitmap from 1 to 0
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m.AggregatePublic.Sub(m.publics[i]) |
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} |
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} |
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return nil |
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} |
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// SetBit enables (enable: true) or disables (enable: false) the bit
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// in the participation Bitmap of the given cosigner.
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func (m *Mask) SetBit(i int, enable bool) error { |
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if i >= len(m.publics) { |
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return errors.New("index out of range") |
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} |
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byt := i >> 3 |
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msk := byte(1) << uint(i&7) |
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if ((m.Bitmap[byt] & msk) == 0) && enable { |
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m.Bitmap[byt] ^= msk // flip bit in Bitmap from 0 to 1
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m.AggregatePublic.Add(m.publics[i]) |
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} |
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if ((m.Bitmap[byt] & msk) != 0) && !enable { |
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m.Bitmap[byt] ^= msk // flip bit in Bitmap from 1 to 0
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m.AggregatePublic.Sub(m.publics[i]) |
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} |
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return nil |
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} |
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// GetPubKeyFromMask will return pubkeys which masked either zero or one depending on the flag
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// it is used to show which signers are signed or not in the cosign message
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func (m *Mask) GetPubKeyFromMask(flag bool) []*bls.PublicKey { |
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pubKeys := []*bls.PublicKey{} |
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for i := range m.publics { |
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byt := i >> 3 |
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msk := byte(1) << uint(i&7) |
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if flag == true { |
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if (m.Bitmap[byt] & msk) != 0 { |
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pubKeys = append(pubKeys, m.publics[i]) |
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} |
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} else { |
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if (m.Bitmap[byt] & msk) == 0 { |
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pubKeys = append(pubKeys, m.publics[i]) |
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} |
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} |
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} |
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return pubKeys |
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} |
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// IndexEnabled checks whether the given index is enabled in the Bitmap or not.
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func (m *Mask) IndexEnabled(i int) (bool, error) { |
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if i >= len(m.publics) { |
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return false, errors.New("index out of range") |
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} |
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byt := i >> 3 |
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msk := byte(1) << uint(i&7) |
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return ((m.Bitmap[byt] & msk) != 0), nil |
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} |
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// KeyEnabled checks whether the index, corresponding to the given key, is
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// enabled in the Bitmap or not.
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func (m *Mask) KeyEnabled(public *bls.PublicKey) (bool, error) { |
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for i, key := range m.publics { |
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if key.IsEqual(public) { |
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return m.IndexEnabled(i) |
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} |
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} |
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return false, errors.New("key not found") |
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} |
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// SetKey set the bit in the Bitmap for the given cosigner
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func (m *Mask) SetKey(public *bls.PublicKey, enable bool) error { |
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for i, key := range m.publics { |
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if key.IsEqual(public) { |
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return m.SetBit(i, enable) |
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} |
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} |
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return errors.New("key not found") |
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} |
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// CountEnabled returns the number of enabled nodes in the CoSi participation
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// Bitmap.
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func (m *Mask) CountEnabled() int { |
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// hw is hamming weight
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hw := 0 |
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for i := range m.publics { |
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byt := i >> 3 |
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msk := byte(1) << uint(i&7) |
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if (m.Bitmap[byt] & msk) != 0 { |
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hw++ |
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} |
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} |
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return hw |
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} |
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// CountTotal returns the total number of nodes this CoSi instance knows.
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func (m *Mask) CountTotal() int { |
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return len(m.publics) |
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} |
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// AggregateMasks computes the bitwise OR of the two given participation masks.
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func AggregateMasks(a, b []byte) ([]byte, error) { |
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if len(a) != len(b) { |
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return nil, errors.New("mismatching Bitmap lengths") |
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} |
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m := make([]byte, len(a)) |
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for i := range m { |
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m[i] = a[i] | b[i] |
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} |
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return m, nil |
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} |
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// Policy represents a fully customizable cosigning policy deciding what
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// cosigner sets are and aren't sufficient for a collective signature to be
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// considered acceptable to a verifier. The Check method may inspect the set of
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// participants that cosigned by invoking cosi.Mask and/or cosi.MaskBit, and may
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// use any other relevant contextual information (e.g., how security-critical
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// the operation relying on the collective signature is) in determining whether
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// the collective signature was produced by an acceptable set of cosigners.
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type Policy interface { |
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Check(m *Mask) bool |
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} |
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// CompletePolicy is the default policy requiring that all participants have
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// cosigned to make a collective signature valid.
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type CompletePolicy struct { |
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} |
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// Check verifies that all participants have contributed to a collective
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// signature.
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func (p CompletePolicy) Check(m *Mask) bool { |
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return m.CountEnabled() == m.CountTotal() |
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} |
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// ThresholdPolicy allows to specify a simple t-of-n policy requring that at
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// least the given threshold number of participants t have cosigned to make a
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// collective signature valid.
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type ThresholdPolicy struct { |
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thold int |
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} |
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// NewThresholdPolicy returns a new ThresholdPolicy with the given threshold.
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func NewThresholdPolicy(thold int) *ThresholdPolicy { |
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return &ThresholdPolicy{thold: thold} |
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} |
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// Check verifies that at least a threshold number of participants have
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// contributed to a collective signature.
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func (p ThresholdPolicy) Check(m *Mask) bool { |
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return m.CountEnabled() >= p.thold |
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} |
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