# key

# Mnemonic

Bytom already supports the BIP39 protocol. Learn specific information about the protocol:https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki

# Seed generates private key

  • Input: A seed with a length of 64. The source of the seed can be randomly generated or calculated from the mnemonic.
  • Output: a private key of a length of 64
$ xprv = hmac(sha512, seed, []byte{'R', 'o', 'o', 't'})
$ xprv[0] &= 248
$ xprv[31] &= 31
$ xprv[31] |= 64

# Private key generates public key

  • Input: a private key of length 64
  • Output: a public key of length 64
$ xpub[:32] = edwards25519.GeScalarMultBase(xprv[:32])
$ xpub[32:] = xprv[32:]

# Sub-private key derivates from private key

  • Input: private key with a length of 64, byte array of derivation path
  • Output: sub-private key with a length of 64
$ xpub = xprv.XPub()
$ child_xprv = hmac(sha512, []byte{'N'} + xpub[:32] + derive_path, xpub[32:])
$ child_xprv[0] &= 248
$ child_xprv[29] &= 1
$ child_xprv[30] = 0
$ child_xprv[31] = 0
$
$ carry = 0
$ for i := 0; i < 32; i++ {
$     sum := int(xprv[i]) + int(child_xprv[i]) + carry
$     child_xprv[i] = byte(sum & 0xff)
$     carry = (sum >> 8)
$ }

# Sub-public keyderivates from public key

  • Input: private key with a length of 64, byte array of derivation path
  • Output: sub-private key with a length of 64
$ child_xpub = hmac(sha512, []byte{'N'} + xpub[:32] + derive_path, xpub[32:])
$ child_xpub[0] &= 248
$ child_xpub[29] &= 1
$ child_xpub[30] = 0
$ child_xpub[31] = 0
$ f = edwards25519.GeScalarMultBase(child_xpub[:32])
$ p = edwards25519.Point(xpub[:32])
$ child_xpub[:32] = edwards25519.AddPoint(p, f)

# The private key is expanded to the private key for signing

  • Input: private key of a length of 64
  • Output: Extended private key with a length of 64
$ expanded = hmac(sha512, xprv, []byte{'E', 'x', 'p', 'a', 'n', 'd'})
$ expanded[:32] = xprv[:32]
Last Updated: 7/28/2021, 5:47:49 PM