package secp256k1 import ( "bytes" "crypto/sha256" "crypto/subtle" "fmt" "io" "math/big" secp256k1 "github.com/btcsuite/btcd/btcec" "golang.org/x/crypto/ripemd160" // nolint: staticcheck // necessary for Bitcoin address format "github.com/tendermint/tendermint/crypto" ) var _ crypto.PrivKey = PrivKey{} const ( PrivKeySize = 32 keyType = "secp256k1" ) // PrivKey implements PrivKey. type PrivKey []byte // Bytes returns the byte representation of the Private Key. func (privKey PrivKey) Bytes() []byte { return []byte(privKey) } // PubKey performs the point-scalar multiplication from the privKey on the // generator point to get the pubkey. func (privKey PrivKey) PubKey() crypto.PubKey { _, pubkeyObject := secp256k1.PrivKeyFromBytes(secp256k1.S256(), privKey) return PubKey(pubkeyObject.SerializeCompressed()) } // Equals - you probably don't need to use this. // Runs in constant time based on length of the keys. func (privKey PrivKey) Equals(other crypto.PrivKey) bool { if otherSecp, ok := other.(PrivKey); ok { return subtle.ConstantTimeCompare(privKey[:], otherSecp[:]) == 1 } return false } func (privKey PrivKey) Type() string { return keyType } // GenPrivKey generates a new ECDSA private key on curve secp256k1 private key. // It uses OS randomness to generate the private key. func GenPrivKey() PrivKey { return genPrivKey(crypto.CReader()) } // genPrivKey generates a new secp256k1 private key using the provided reader. func genPrivKey(rand io.Reader) PrivKey { var privKeyBytes [PrivKeySize]byte d := new(big.Int) for { privKeyBytes = [PrivKeySize]byte{} _, err := io.ReadFull(rand, privKeyBytes[:]) if err != nil { panic(err) } d.SetBytes(privKeyBytes[:]) // break if we found a valid point (i.e. > 0 and < N == curverOrder) isValidFieldElement := 0 < d.Sign() && d.Cmp(secp256k1.S256().N) < 0 if isValidFieldElement { break } } return PrivKey(privKeyBytes[:]) } var one = new(big.Int).SetInt64(1) // GenPrivKeySecp256k1 hashes the secret with SHA2, and uses // that 32 byte output to create the private key. // // It makes sure the private key is a valid field element by setting: // // c = sha256(secret) // k = (c mod (n − 1)) + 1, where n = curve order. // // NOTE: secret should be the output of a KDF like bcrypt, // if it's derived from user input. func GenPrivKeySecp256k1(secret []byte) PrivKey { secHash := sha256.Sum256(secret) // to guarantee that we have a valid field element, we use the approach of: // "Suite B Implementer’s Guide to FIPS 186-3", A.2.1 // https://apps.nsa.gov/iaarchive/library/ia-guidance/ia-solutions-for-classified/algorithm-guidance/suite-b-implementers-guide-to-fips-186-3-ecdsa.cfm // see also https://github.com/golang/go/blob/0380c9ad38843d523d9c9804fe300cb7edd7cd3c/src/crypto/ecdsa/ecdsa.go#L89-L101 fe := new(big.Int).SetBytes(secHash[:]) n := new(big.Int).Sub(secp256k1.S256().N, one) fe.Mod(fe, n) fe.Add(fe, one) feB := fe.Bytes() privKey32 := make([]byte, PrivKeySize) // copy feB over to fixed 32 byte privKey32 and pad (if necessary) copy(privKey32[32-len(feB):32], feB) return PrivKey(privKey32) } //------------------------------------- var _ crypto.PubKey = PubKey{} // PubKeySize is comprised of 32 bytes for one field element // (the x-coordinate), plus one byte for the parity of the y-coordinate. const PubKeySize = 33 // PubKey implements crypto.PubKey. // It is the compressed form of the pubkey. The first byte depends is a 0x02 byte // if the y-coordinate is the lexicographically largest of the two associated with // the x-coordinate. Otherwise the first byte is a 0x03. // This prefix is followed with the x-coordinate. type PubKey []byte // Address returns a Bitcoin style addresses: RIPEMD160(SHA256(pubkey)) func (pubKey PubKey) Address() crypto.Address { if len(pubKey) != PubKeySize { panic("length of pubkey is incorrect") } hasherSHA256 := sha256.New() hasherSHA256.Write(pubKey) // does not error sha := hasherSHA256.Sum(nil) hasherRIPEMD160 := ripemd160.New() hasherRIPEMD160.Write(sha) // does not error return crypto.Address(hasherRIPEMD160.Sum(nil)) } // Bytes returns the pubkey byte format. func (pubKey PubKey) Bytes() []byte { return []byte(pubKey) } func (pubKey PubKey) String() string { return fmt.Sprintf("PubKeySecp256k1{%X}", []byte(pubKey)) } func (pubKey PubKey) Type() string { return keyType } func (pubKey PubKey) Equals(other crypto.PubKey) bool { if otherSecp, ok := other.(PubKey); ok { return bytes.Equal(pubKey[:], otherSecp[:]) } return false }