+++ /dev/null
-package chainkd
-
-import (
- "crypto/hmac"
- "crypto/rand"
- "crypto/sha512"
- "io"
-
- "github.com/vapor/crypto/ed25519"
- "github.com/vapor/crypto/ed25519/ecmath"
-)
-
-type (
- //XPrv external private key
- XPrv [64]byte
- //XPub external public key
- XPub [64]byte
-)
-
-// NewXPrv takes a source of random bytes and produces a new XPrv.
-// If r is nil, crypto/rand.Reader is used.
-func NewXPrv(r io.Reader) (xprv XPrv, err error) {
- if r == nil {
- r = rand.Reader
- }
- var entropy [64]byte
- _, err = io.ReadFull(r, entropy[:])
- if err != nil {
- return xprv, err
- }
- return RootXPrv(entropy[:]), nil
-}
-
-// RootXPrv takes a seed binary string and produces a new xprv.
-func RootXPrv(seed []byte) (xprv XPrv) {
- h := hmac.New(sha512.New, []byte{'R', 'o', 'o', 't'})
- h.Write(seed)
- h.Sum(xprv[:0])
- pruneRootScalar(xprv[:32])
- return
-}
-
-// XPub derives an extended public key from a given xprv.
-func (xprv XPrv) XPub() (xpub XPub) {
- var scalar ecmath.Scalar
- copy(scalar[:], xprv[:32])
-
- var P ecmath.Point
- P.ScMulBase(&scalar)
- buf := P.Encode()
-
- copy(xpub[:32], buf[:])
- copy(xpub[32:], xprv[32:])
-
- return
-}
-
-// Child derives a child xprv based on `selector` string and `hardened` flag.
-// If `hardened` is false, child xpub can be derived independently
-// from the parent xpub without using the parent xprv.
-// If `hardened` is true, child key can only be derived from the parent xprv.
-func (xprv XPrv) Child(sel []byte, hardened bool) XPrv {
- if hardened {
- return xprv.hardenedChild(sel)
- }
- return xprv.nonhardenedChild(sel)
-}
-
-func (xprv XPrv) hardenedChild(sel []byte) (res XPrv) {
- h := hmac.New(sha512.New, xprv[32:])
- h.Write([]byte{'H'})
- h.Write(xprv[:32])
- h.Write(sel)
- h.Sum(res[:0])
- pruneRootScalar(res[:32])
- return
-}
-
-func (xprv XPrv) nonhardenedChild(sel []byte) (res XPrv) {
- xpub := xprv.XPub()
-
- h := hmac.New(sha512.New, xpub[32:])
- h.Write([]byte{'N'})
- h.Write(xpub[:32])
- h.Write(sel)
- h.Sum(res[:0])
-
- pruneIntermediateScalar(res[:32])
-
- // Unrolled the following loop:
- // var carry int
- // carry = 0
- // for i := 0; i < 32; i++ {
- // sum := int(xprv[i]) + int(res[i]) + carry
- // res[i] = byte(sum & 0xff)
- // carry = (sum >> 8)
- // }
-
- sum := int(0)
-
- sum = int(xprv[0]) + int(res[0]) + (sum >> 8)
- res[0] = byte(sum & 0xff)
- sum = int(xprv[1]) + int(res[1]) + (sum >> 8)
- res[1] = byte(sum & 0xff)
- sum = int(xprv[2]) + int(res[2]) + (sum >> 8)
- res[2] = byte(sum & 0xff)
- sum = int(xprv[3]) + int(res[3]) + (sum >> 8)
- res[3] = byte(sum & 0xff)
- sum = int(xprv[4]) + int(res[4]) + (sum >> 8)
- res[4] = byte(sum & 0xff)
- sum = int(xprv[5]) + int(res[5]) + (sum >> 8)
- res[5] = byte(sum & 0xff)
- sum = int(xprv[6]) + int(res[6]) + (sum >> 8)
- res[6] = byte(sum & 0xff)
- sum = int(xprv[7]) + int(res[7]) + (sum >> 8)
- res[7] = byte(sum & 0xff)
- sum = int(xprv[8]) + int(res[8]) + (sum >> 8)
- res[8] = byte(sum & 0xff)
- sum = int(xprv[9]) + int(res[9]) + (sum >> 8)
- res[9] = byte(sum & 0xff)
- sum = int(xprv[10]) + int(res[10]) + (sum >> 8)
- res[10] = byte(sum & 0xff)
- sum = int(xprv[11]) + int(res[11]) + (sum >> 8)
- res[11] = byte(sum & 0xff)
- sum = int(xprv[12]) + int(res[12]) + (sum >> 8)
- res[12] = byte(sum & 0xff)
- sum = int(xprv[13]) + int(res[13]) + (sum >> 8)
- res[13] = byte(sum & 0xff)
- sum = int(xprv[14]) + int(res[14]) + (sum >> 8)
- res[14] = byte(sum & 0xff)
- sum = int(xprv[15]) + int(res[15]) + (sum >> 8)
- res[15] = byte(sum & 0xff)
- sum = int(xprv[16]) + int(res[16]) + (sum >> 8)
- res[16] = byte(sum & 0xff)
- sum = int(xprv[17]) + int(res[17]) + (sum >> 8)
- res[17] = byte(sum & 0xff)
- sum = int(xprv[18]) + int(res[18]) + (sum >> 8)
- res[18] = byte(sum & 0xff)
- sum = int(xprv[19]) + int(res[19]) + (sum >> 8)
- res[19] = byte(sum & 0xff)
- sum = int(xprv[20]) + int(res[20]) + (sum >> 8)
- res[20] = byte(sum & 0xff)
- sum = int(xprv[21]) + int(res[21]) + (sum >> 8)
- res[21] = byte(sum & 0xff)
- sum = int(xprv[22]) + int(res[22]) + (sum >> 8)
- res[22] = byte(sum & 0xff)
- sum = int(xprv[23]) + int(res[23]) + (sum >> 8)
- res[23] = byte(sum & 0xff)
- sum = int(xprv[24]) + int(res[24]) + (sum >> 8)
- res[24] = byte(sum & 0xff)
- sum = int(xprv[25]) + int(res[25]) + (sum >> 8)
- res[25] = byte(sum & 0xff)
- sum = int(xprv[26]) + int(res[26]) + (sum >> 8)
- res[26] = byte(sum & 0xff)
- sum = int(xprv[27]) + int(res[27]) + (sum >> 8)
- res[27] = byte(sum & 0xff)
- sum = int(xprv[28]) + int(res[28]) + (sum >> 8)
- res[28] = byte(sum & 0xff)
- sum = int(xprv[29]) + int(res[29]) + (sum >> 8)
- res[29] = byte(sum & 0xff)
- sum = int(xprv[30]) + int(res[30]) + (sum >> 8)
- res[30] = byte(sum & 0xff)
- sum = int(xprv[31]) + int(res[31]) + (sum >> 8)
- res[31] = byte(sum & 0xff)
-
- if (sum >> 8) != 0 {
- panic("sum does not fit in 256-bit int")
- }
- return
-}
-
-// Child derives a child xpub based on `selector` string.
-// The corresponding child xprv can be derived from the parent xprv
-// using non-hardened derivation: `parentxprv.Child(sel, false)`.
-func (xpub XPub) Child(sel []byte) (res XPub) {
- h := hmac.New(sha512.New, xpub[32:])
- h.Write([]byte{'N'})
- h.Write(xpub[:32])
- h.Write(sel)
- h.Sum(res[:0])
-
- pruneIntermediateScalar(res[:32])
-
- var (
- f ecmath.Scalar
- F ecmath.Point
- )
- copy(f[:], res[:32])
- F.ScMulBase(&f)
-
- var (
- pubkey [32]byte
- P ecmath.Point
- )
- copy(pubkey[:], xpub[:32])
- _, ok := P.Decode(pubkey)
- if !ok {
- panic("XPub should have been validated on initialization")
- }
-
- P.Add(&P, &F)
- pubkey = P.Encode()
- copy(res[:32], pubkey[:])
-
- return
-}
-
-// Derive generates a child xprv by recursively deriving
-// non-hardened child xprvs over the list of selectors:
-// `Derive([a,b,c,...]) == Child(a).Child(b).Child(c)...`
-func (xprv XPrv) Derive(path [][]byte) XPrv {
- res := xprv
- for _, p := range path {
- res = res.Child(p, false)
- }
- return res
-}
-
-// Derive generates a child xpub by recursively deriving
-// non-hardened child xpubs over the list of selectors:
-// `Derive([a,b,c,...]) == Child(a).Child(b).Child(c)...`
-func (xpub XPub) Derive(path [][]byte) XPub {
- res := xpub
- for _, p := range path {
- res = res.Child(p)
- }
- return res
-}
-
-// Sign creates an EdDSA signature using expanded private key
-// derived from the xprv.
-func (xprv XPrv) Sign(msg []byte) []byte {
- return Ed25519InnerSign(xprv.ExpandedPrivateKey(), msg)
-}
-
-// Verify checks an EdDSA signature using public key
-// extracted from the first 32 bytes of the xpub.
-func (xpub XPub) Verify(msg []byte, sig []byte) bool {
- return ed25519.Verify(xpub.PublicKey(), msg, sig)
-}
-
-// ExpandedPrivateKey generates a 64-byte key where
-// the first half is the scalar copied from xprv,
-// and the second half is the `prefix` is generated via PRF
-// from the xprv.
-func (xprv XPrv) ExpandedPrivateKey() ExpandedPrivateKey {
- var res [64]byte
- h := hmac.New(sha512.New, []byte{'E', 'x', 'p', 'a', 'n', 'd'})
- h.Write(xprv[:])
- h.Sum(res[:0])
- copy(res[:32], xprv[:32])
- return res[:]
-}
-
-// PublicKey extracts the ed25519 public key from an xpub.
-func (xpub XPub) PublicKey() ed25519.PublicKey {
- return ed25519.PublicKey(xpub[:32])
-}
-
-// s must be >= 32 bytes long and gets rewritten in place.
-// This is NOT the same pruning as in Ed25519: it additionally clears the third
-// highest bit to ensure subkeys do not overflow the second highest bit.
-func pruneRootScalar(s []byte) {
- s[0] &= 248
- s[31] &= 31 // clear top 3 bits
- s[31] |= 64 // set second highest bit
-}
-
-// Clears lowest 3 bits and highest 23 bits of `f`.
-func pruneIntermediateScalar(f []byte) {
- f[0] &= 248 // clear bottom 3 bits
- f[29] &= 1 // clear 7 high bits
- f[30] = 0 // clear 8 bits
- f[31] = 0 // clear 8 bits
-}
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