// NewMasterHDKey computes the root HD key from the given seed, key and private
// version.
func NewMaster(seed, key []byte, version uint16) (*HDKey, error) {
if len(seed) < MinSeedSize || len(seed) > MaxSeedSize {
return nil, ErrInvalidSeedLength
}
// il, ir = HMAC-512(key, seed)
il, chainCode := util.HMAC512Split(key, seed)
defer func() { util.Zero(il); util.Zero(chainCode) }()
// Left 32 bytes becomes master secret key, clean up temporary SecretKey
sk, err := eckey.NewSecretKey(il)
if err != nil {
return nil, ErrUnusableSeed
}
defer sk.Zero()
return newHDSecretKey(version, 0, 0, 0, chainCode, sk), nil
}
// validPublicOrSecretBytes takes a byte slice, assumed to be childKeySize
// bytes in length, and determines whether the associated public or private key
// corresponds to a valid point on secp256k1 curve.
func validPublicOrSecretBytes(b []byte) error {
// Assume derived key is a CompressedPublicKey if first byte is not 0.
if b[0] != 0 {
cpk, err := eckey.NewCompressedPublicKey(b)
if err != nil {
return nil
}
_, err = cpk.Uncompress()
return err
}
// Otherwise verify SecretKey
if _, err := eckey.NewSecretKey(b[1:]); err != nil {
return err
}
return nil
}