extendedkey.go

/*

 */

package hdwallet

import (
	"fmt"
	"errors"
)
const (
	// RecommendedSeedLen is the recommended length in bytes for a seed
	// to a master node.
	RecommendedSeedLen = 32 // 256 bits

	// HardenedKeyStart is the index at which a hardended key starts.  Each
	// extended key has 2^31 normal child keys and 2^31 hardned child keys.
	// Thus the range for normal child keys is [0, 2^31 - 1] and the range
	// for hardened child keys is [2^31, 2^32 - 1].
	HardenedKeyStart = 0x80000000 // 2^31

	// MinSeedBytes is the minimum number of bytes allowed for a seed to
	// a master node.
	MinSeedBytes = 16 // 128 bits

	// MaxSeedBytes is the maximum number of bytes allowed for a seed to
	// a master node.
	MaxSeedBytes = 64 // 512 bits

	// serializedKeyLen is the length of a serialized public or private
	// extended key.  It consists of 4 bytes version, 1 byte depth, 4 bytes
	// fingerprint, 4 bytes child number, 32 bytes chain code, and 33 bytes
	// public/private key data.
	serializedKeyLen = 4 + 1 + 4 + 4 + 32 + 33 // 78 bytes

	// maxUint8 is the max positive integer which can be serialized in a uint8
	maxUint8 = 1<<8 - 1
)

var (
	// ErrDeriveHardFromPublic describes an error in which the caller
	// attempted to derive a hardened extended key from a public key.
	ErrDeriveHardFromPublic = errors.New("cannot derive a hardened key " +
		"from a public key")

	// ErrDeriveBeyondMaxDepth describes an error in which the caller
	// has attempted to derive more than 255 keys from a root key.
	ErrDeriveBeyondMaxDepth = errors.New("cannot derive a key with more than " +
		"255 indices in its path")

	// ErrNotPrivExtKey describes an error in which the caller attempted
	// to extract a private key from a public extended key.
	ErrNotPrivExtKey = errors.New("unable to create private keys from a " +
		"public extended key")

	// ErrInvalidChild describes an error in which the child at a specific
	// index is invalid due to the derived key falling outside of the valid
	// range for secp256k1 private keys.  This error indicates the caller
	// should simply ignore the invalid child extended key at this index and
	// increment to the next index.
	ErrInvalidChild = errors.New("the extended key at this index is invalid")

	// ErrUnusableSeed describes an error in which the provided seed is not
	// usable due to the derived key falling outside of the valid range for
	// secp256k1 private keys.  This error indicates the caller must choose
	// another seed.
	ErrUnusableSeed = errors.New("unusable seed")

	// ErrInvalidSeedLen describes an error in which the provided seed or
	// seed length is not in the allowed range.
	ErrInvalidSeedLen = fmt.Errorf("seed length must be between %d and %d "+
		"bits", MinSeedBytes*8, MaxSeedBytes*8)

	// ErrBadChecksum describes an error in which the checksum encoded with
	// a serialized extended key does not match the calculated value.
	ErrBadChecksum = errors.New("bad extended key checksum")

	// ErrInvalidKeyLen describes an error in which the provided serialized
	// key is not the expected length.
	ErrInvalidKeyLen = errors.New("the provided serialized extended key " +
		"length is invalid")
)



// ExtendedKey houses all the information needed to support a hierarchical
// deterministic extended key.  See the package overview documentation for
// more details on how to use extended keys.
type ExtendedKey struct {
	key       []byte // This will be the pubkey for extended pub keys
	pubKey    []byte // This will only be set for extended priv keys
	chainCode []byte
	depth     uint8
	parentFP  []byte
	childNum  uint32
	isPrivate bool
}

// NewExtendedKey returns a new instance of an extended key with the given
// fields.  No error checking is performed here as it's only intended to be a
// convenience method used to create a populated struct. This function should
// only by used by applications that need to create custom ExtendedKeys. All
// other applications should just use NewMaster, Child, or Neuter.
func NewExtendedKey(key, chainCode, parentFP []byte, depth uint8,
	childNum uint32, isPrivate bool) *ExtendedKey {

	// NOTE: The pubKey field is intentionally left nil so it is only
	// computed and memoized as required.
	return &ExtendedKey{
		key:       key,
		chainCode: chainCode,
		depth:     depth,
		parentFP:  parentFP,
		childNum:  childNum,
		isPrivate: isPrivate,
	}
}