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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
amino "github.com/tendermint/go-amino"
"github.com/tendermint/tendermint/crypto"
)
//-------------------------------------
const (
PrivKeyAminoName = "tendermint/PrivKeySecp256k1"
PubKeyAminoName = "tendermint/PubKeySecp256k1"
)
var cdc = amino.NewCodec()
func init() {
cdc.RegisterInterface((*crypto.PubKey)(nil), nil)
cdc.RegisterConcrete(PubKeySecp256k1{},
PubKeyAminoName, nil)
cdc.RegisterInterface((*crypto.PrivKey)(nil), nil)
cdc.RegisterConcrete(PrivKeySecp256k1{},
PrivKeyAminoName, nil)
}
//-------------------------------------
var _ crypto.PrivKey = PrivKeySecp256k1{}
// PrivKeySecp256k1 implements PrivKey.
type PrivKeySecp256k1 [32]byte
// Bytes marshalls the private key using amino encoding.
func (privKey PrivKeySecp256k1) Bytes() []byte {
return cdc.MustMarshalBinaryBare(privKey)
}
// PubKey performs the point-scalar multiplication from the privKey on the
// generator point to get the pubkey.
func (privKey PrivKeySecp256k1) PubKey() crypto.PubKey {
_, pubkeyObject := secp256k1.PrivKeyFromBytes(secp256k1.S256(), privKey[:])
var pubkeyBytes PubKeySecp256k1
copy(pubkeyBytes[:], pubkeyObject.SerializeCompressed())
return pubkeyBytes
}
// Equals - you probably don't need to use this.
// Runs in constant time based on length of the keys.
func (privKey PrivKeySecp256k1) Equals(other crypto.PrivKey) bool {
if otherSecp, ok := other.(PrivKeySecp256k1); ok {
return subtle.ConstantTimeCompare(privKey[:], otherSecp[:]) == 1
}
return false
}
// GenPrivKey generates a new ECDSA private key on curve secp256k1 private key.
// It uses OS randomness to generate the private key.
func GenPrivKey() PrivKeySecp256k1 {
return genPrivKey(crypto.CReader())
}
// genPrivKey generates a new secp256k1 private key using the provided reader.
func genPrivKey(rand io.Reader) PrivKeySecp256k1 {
var privKeyBytes [32]byte
d := new(big.Int)
for {
privKeyBytes = [32]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 PrivKeySecp256k1(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) PrivKeySecp256k1 {
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()
var privKey32 [32]byte
// copy feB over to fixed 32 byte privKey32 and pad (if necessary)
copy(privKey32[32-len(feB):32], feB)
return PrivKeySecp256k1(privKey32)
}
//-------------------------------------
var _ crypto.PubKey = PubKeySecp256k1{}
// PubKeySecp256k1Size is comprised of 32 bytes for one field element
// (the x-coordinate), plus one byte for the parity of the y-coordinate.
const PubKeySecp256k1Size = 33
// PubKeySecp256k1 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 PubKeySecp256k1 [PubKeySecp256k1Size]byte
// Address returns a Bitcoin style addresses: RIPEMD160(SHA256(pubkey))
func (pubKey PubKeySecp256k1) Address() crypto.Address {
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 marshalled with amino encoding.
func (pubKey PubKeySecp256k1) Bytes() []byte {
bz, err := cdc.MarshalBinaryBare(pubKey)
if err != nil {
panic(err)
}
return bz
}
func (pubKey PubKeySecp256k1) String() string {
return fmt.Sprintf("PubKeySecp256k1{%X}", pubKey[:])
}
func (pubKey PubKeySecp256k1) Equals(other crypto.PubKey) bool {
if otherSecp, ok := other.(PubKeySecp256k1); ok {
return bytes.Equal(pubKey[:], otherSecp[:])
}
return false
}