// // Copyright Coinbase, Inc. All Rights Reserved. // // SPDX-License-Identifier: Apache-2.0 // package bls_sig import ( "fmt" ) const ( // Domain separation tag for basic signatures // according to section 4.2.1 in // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 blsSignatureBasicDst = "BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_NUL_" // Domain separation tag for basic signatures // according to section 4.2.2 in // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 blsSignatureAugDst = "BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_AUG_" // Domain separation tag for proof of possession signatures // according to section 4.2.3 in // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 blsSignaturePopDst = "BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_POP_" // Domain separation tag for proof of possession proofs // according to section 4.2.3 in // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 blsPopProofDst = "BLS_POP_BLS12381G2_XMD:SHA-256_SSWU_RO_POP_" ) type BlsScheme interface { Keygen() (*PublicKey, *SecretKey, error) KeygenWithSeed(ikm []byte) (*PublicKey, *SecretKey, error) Sign(sk *SecretKey, msg []byte) (*Signature, error) Verify(pk *PublicKey, msg []byte, sig *Signature) bool AggregateVerify(pks []*PublicKey, msgs [][]byte, sigs []*Signature) bool } // generateKeys creates 32 bytes of random data to be fed to // generateKeysWithSeed func generateKeys() (*PublicKey, *SecretKey, error) { ikm, err := generateRandBytes(32) if err != nil { return nil, nil, err } return generateKeysWithSeed(ikm) } // generateKeysWithSeed generates a BLS key pair given input key material (ikm) func generateKeysWithSeed(ikm []byte) (*PublicKey, *SecretKey, error) { sk, err := new(SecretKey).Generate(ikm) if err != nil { return nil, nil, err } pk, err := sk.GetPublicKey() if err != nil { return nil, nil, err } return pk, sk, nil } // thresholdGenerateKeys will generate random secret key shares and the corresponding public key func thresholdGenerateKeys(threshold, total uint) (*PublicKey, []*SecretKeyShare, error) { pk, sk, err := generateKeys() if err != nil { return nil, nil, err } shares, err := thresholdizeSecretKey(sk, threshold, total) if err != nil { return nil, nil, err } return pk, shares, nil } // thresholdGenerateKeysWithSeed will generate random secret key shares and the corresponding public key // using the corresponding seed `ikm` func thresholdGenerateKeysWithSeed(ikm []byte, threshold, total uint) (*PublicKey, []*SecretKeyShare, error) { pk, sk, err := generateKeysWithSeed(ikm) if err != nil { return nil, nil, err } shares, err := thresholdizeSecretKey(sk, threshold, total) if err != nil { return nil, nil, err } return pk, shares, nil } // SigBasic is minimal-pubkey-size scheme that doesn't support FastAggregateVerificiation. // see: https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03#section-4.2.1 type SigBasic struct { dst string } // Creates a new BLS basic signature scheme with the standard domain separation tag used for signatures. func NewSigBasic() *SigBasic { return &SigBasic{dst: blsSignatureBasicDst} } // Creates a new BLS basic signature scheme with a custom domain separation tag used for signatures. func NewSigBasicWithDst(signDst string) *SigBasic { return &SigBasic{dst: signDst} } // Creates a new BLS key pair func (b SigBasic) Keygen() (*PublicKey, *SecretKey, error) { return generateKeys() } // Creates a new BLS key pair // Input key material (ikm) MUST be at least 32 bytes long, // but it MAY be longer. func (b SigBasic) KeygenWithSeed(ikm []byte) (*PublicKey, *SecretKey, error) { return generateKeysWithSeed(ikm) } // ThresholdKeyGen generates a public key and `total` secret key shares such that // `threshold` of them can be combined in signatures func (b SigBasic) ThresholdKeygen(threshold, total uint) (*PublicKey, []*SecretKeyShare, error) { return thresholdGenerateKeys(threshold, total) } // ThresholdKeyGen generates a public key and `total` secret key shares such that // `threshold` of them can be combined in signatures func (b SigBasic) ThresholdKeygenWithSeed(ikm []byte, threshold, total uint) (*PublicKey, []*SecretKeyShare, error) { return thresholdGenerateKeysWithSeed(ikm, threshold, total) } // Computes a signature in G2 from sk, a secret key, and a message func (b SigBasic) Sign(sk *SecretKey, msg []byte) (*Signature, error) { return sk.createSignature(msg, b.dst) } // Compute a partial signature in G2 that can be combined with other partial signature func (b SigBasic) PartialSign(sks *SecretKeyShare, msg []byte) (*PartialSignature, error) { return sks.partialSign(msg, b.dst) } // CombineSignatures takes partial signatures to yield a completed signature func (b SigBasic) CombineSignatures(sigs ...*PartialSignature) (*Signature, error) { return combineSigs(sigs) } // Checks that a signature is valid for the message under the public key pk func (b SigBasic) Verify(pk *PublicKey, msg []byte, sig *Signature) (bool, error) { return pk.verifySignature(msg, sig, b.dst) } // The AggregateVerify algorithm checks an aggregated signature over // several (PK, message, signature) pairs. // Each message must be different or this will return false. // See section 3.1.1 from // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 func (b SigBasic) AggregateVerify(pks []*PublicKey, msgs [][]byte, sigs []*Signature) (bool, error) { if !allRowsUnique(msgs) { return false, fmt.Errorf("all messages must be distinct") } asig, err := aggregateSignatures(sigs...) if err != nil { return false, err } return asig.aggregateVerify(pks, msgs, b.dst) } // SigAug is minimal-pubkey-size scheme that doesn't support FastAggregateVerificiation. // see: https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03#section-4.2.2 type SigAug struct { dst string } // Creates a new BLS message augmentation signature scheme with the standard domain separation tag used for signatures. func NewSigAug() *SigAug { return &SigAug{dst: blsSignatureAugDst} } // Creates a new BLS message augmentation signature scheme with a custom domain separation tag used for signatures. func NewSigAugWithDst(signDst string) *SigAug { return &SigAug{dst: signDst} } // Creates a new BLS key pair func (b SigAug) Keygen() (*PublicKey, *SecretKey, error) { return generateKeys() } // Creates a new BLS secret key // Input key material (ikm) MUST be at least 32 bytes long, // but it MAY be longer. func (b SigAug) KeygenWithSeed(ikm []byte) (*PublicKey, *SecretKey, error) { return generateKeysWithSeed(ikm) } // ThresholdKeyGen generates a public key and `total` secret key shares such that // `threshold` of them can be combined in signatures func (b SigAug) ThresholdKeygen(threshold, total uint) (*PublicKey, []*SecretKeyShare, error) { return thresholdGenerateKeys(threshold, total) } // ThresholdKeyGen generates a public key and `total` secret key shares such that // `threshold` of them can be combined in signatures func (b SigAug) ThresholdKeygenWithSeed(ikm []byte, threshold, total uint) (*PublicKey, []*SecretKeyShare, error) { return thresholdGenerateKeysWithSeed(ikm, threshold, total) } // Computes a signature in G1 from sk, a secret key, and a message // See section 3.2.1 from // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 func (b SigAug) Sign(sk *SecretKey, msg []byte) (*Signature, error) { if len(msg) == 0 { return nil, fmt.Errorf("message cannot be empty or nil") } pk, err := sk.GetPublicKey() if err != nil { return nil, err } bytes, err := pk.MarshalBinary() if err != nil { return nil, fmt.Errorf("MarshalBinary failed") } bytes = append(bytes, msg...) return sk.createSignature(bytes, b.dst) } // Compute a partial signature in G2 that can be combined with other partial signature func (b SigAug) PartialSign(sks *SecretKeyShare, pk *PublicKey, msg []byte) (*PartialSignature, error) { if len(msg) == 0 { return nil, fmt.Errorf("message cannot be empty or nil") } bytes, err := pk.MarshalBinary() if err != nil { return nil, fmt.Errorf("MarshalBinary failed") } bytes = append(bytes, msg...) return sks.partialSign(bytes, b.dst) } // CombineSignatures takes partial signatures to yield a completed signature func (b SigAug) CombineSignatures(sigs ...*PartialSignature) (*Signature, error) { return combineSigs(sigs) } // Checks that a signature is valid for the message under the public key pk // See section 3.2.2 from // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 func (b SigAug) Verify(pk *PublicKey, msg []byte, sig *Signature) (bool, error) { bytes, err := pk.MarshalBinary() if err != nil { return false, err } bytes = append(bytes, msg...) return pk.verifySignature(bytes, sig, b.dst) } // The AggregateVerify algorithm checks an aggregated signature over // several (PK, message, signature) pairs. // See section 3.2.3 from // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 func (b SigAug) AggregateVerify(pks []*PublicKey, msgs [][]byte, sigs []*Signature) (bool, error) { if len(pks) != len(msgs) { return false, fmt.Errorf("the number of public keys does not match the number of messages: %v != %v", len(pks), len(msgs)) } data := make([][]byte, len(msgs)) for i, msg := range msgs { bytes, err := pks[i].MarshalBinary() if err != nil { return false, err } data[i] = append(bytes, msg...) } asig, err := aggregateSignatures(sigs...) if err != nil { return false, err } return asig.aggregateVerify(pks, data, b.dst) } // SigEth2 supports signatures on Eth2. // Internally is an alias for SigPop type SigEth2 = SigPop // NewSigEth2 Creates a new BLS ETH2 signature scheme with the standard domain separation tag used for signatures. func NewSigEth2() *SigEth2 { return NewSigPop() } // SigPop is minimal-pubkey-size scheme that supports FastAggregateVerification // and requires using proofs of possession to mitigate rogue-key attacks // see: https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03#section-4.2.3 type SigPop struct { sigDst string popDst string } // Creates a new BLS proof of possession signature scheme with the standard domain separation tag used for signatures. func NewSigPop() *SigPop { return &SigPop{sigDst: blsSignaturePopDst, popDst: blsPopProofDst} } // Creates a new BLS message proof of possession signature scheme with a custom domain separation tag used for signatures. func NewSigPopWithDst(signDst, popDst string) (*SigPop, error) { if signDst == popDst { return nil, fmt.Errorf("domain separation tags cannot be equal") } return &SigPop{sigDst: signDst, popDst: popDst}, nil } // Creates a new BLS key pair func (b SigPop) Keygen() (*PublicKey, *SecretKey, error) { return generateKeys() } // Creates a new BLS secret key // Input key material (ikm) MUST be at least 32 bytes long, // but it MAY be longer. func (b SigPop) KeygenWithSeed(ikm []byte) (*PublicKey, *SecretKey, error) { return generateKeysWithSeed(ikm) } // ThresholdKeyGen generates a public key and `total` secret key shares such that // `threshold` of them can be combined in signatures func (b SigPop) ThresholdKeygen(threshold, total uint) (*PublicKey, []*SecretKeyShare, error) { return thresholdGenerateKeys(threshold, total) } // ThresholdKeyGen generates a public key and `total` secret key shares such that // `threshold` of them can be combined in signatures func (b SigPop) ThresholdKeygenWithSeed(ikm []byte, threshold, total uint) (*PublicKey, []*SecretKeyShare, error) { return thresholdGenerateKeysWithSeed(ikm, threshold, total) } // Computes a signature in G2 from sk, a secret key, and a message // See section 2.6 from // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 func (b SigPop) Sign(sk *SecretKey, msg []byte) (*Signature, error) { return sk.createSignature(msg, b.sigDst) } // Compute a partial signature in G2 that can be combined with other partial signature func (b SigPop) PartialSign(sks *SecretKeyShare, msg []byte) (*PartialSignature, error) { return sks.partialSign(msg, b.sigDst) } // CombineSignatures takes partial signatures to yield a completed signature func (b SigPop) CombineSignatures(sigs ...*PartialSignature) (*Signature, error) { return combineSigs(sigs) } // Checks that a signature is valid for the message under the public key pk // See section 2.7 from // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 func (b SigPop) Verify(pk *PublicKey, msg []byte, sig *Signature) (bool, error) { return pk.verifySignature(msg, sig, b.sigDst) } // The aggregateVerify algorithm checks an aggregated signature over // several (PK, message, signature) pairs. // Each message must be different or this will return false. // See section 3.1.1 from // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 func (b SigPop) AggregateVerify(pks []*PublicKey, msgs [][]byte, sigs []*Signature) (bool, error) { if !allRowsUnique(msgs) { return false, fmt.Errorf("all messages must be distinct") } asig, err := aggregateSignatures(sigs...) if err != nil { return false, err } return asig.aggregateVerify(pks, msgs, b.sigDst) } // Combine many signatures together to form a Multisignature. // Multisignatures can be created when multiple signers jointly // generate signatures over the same message. func (b SigPop) AggregateSignatures(sigs ...*Signature) (*MultiSignature, error) { g1, err := aggregateSignatures(sigs...) if err != nil { return nil, err } return &MultiSignature{value: g1.Value}, nil } // Combine many public keys together to form a Multipublickey. // Multipublickeys are used to verify multisignatures. func (b SigPop) AggregatePublicKeys(pks ...*PublicKey) (*MultiPublicKey, error) { g2, err := aggregatePublicKeys(pks...) if err != nil { return nil, err } return &MultiPublicKey{value: g2.value}, nil } // Checks that a multisignature is valid for the message under the multi public key // Similar to FastAggregateVerify except the keys and signatures have already been // combined. See section 3.3.4 from // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 func (b SigPop) VerifyMultiSignature(pk *MultiPublicKey, msg []byte, sig *MultiSignature) (bool, error) { s := &Signature{Value: sig.value} p := &PublicKey{value: pk.value} return p.verifySignature(msg, s, b.sigDst) } // FastAggregateVerify verifies an aggregated signature against the specified message and set of public keys. // See section 3.3.4 from // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 func (b SigPop) FastAggregateVerify(pks []*PublicKey, msg []byte, asig *Signature) (bool, error) { apk, err := aggregatePublicKeys(pks...) if err != nil { return false, err } return apk.verifySignature(msg, asig, b.sigDst) } // FastAggregateVerifyConstituent aggregates all constituent signatures and the verifies // them against the specified message and public keys // See section 3.3.4 from // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 func (b SigPop) FastAggregateVerifyConstituent(pks []*PublicKey, msg []byte, sigs []*Signature) (bool, error) { // Aggregate the constituent signatures asig, err := aggregateSignatures(sigs...) if err != nil { return false, err } // And verify return b.FastAggregateVerify(pks, msg, asig) } // Create a proof of possession for the corresponding public key. // A proof of possession must be created for each public key to be used // in FastAggregateVerify or a Multipublickey to avoid rogue key attacks. // See section 3.3.2 from // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 func (b SigPop) PopProve(sk *SecretKey) (*ProofOfPossession, error) { return sk.createProofOfPossession(b.popDst) } // verify a proof of possession for the corresponding public key is valid. // A proof of possession must be created for each public key to be used // in FastAggregateVerify or a Multipublickey to avoid rogue key attacks. // See section 3.3.3 from // https://tools.ietf.org/html/draft-irtf-cfrg-bls-signature-03 func (b SigPop) PopVerify(pk *PublicKey, pop2 *ProofOfPossession) (bool, error) { return pop2.verify(pk, b.popDst) }