1 /*Package hdkeychain provides an API for bitcoin hierarchical deterministic extended keys (BIP0032).
2 3 Overview
4 5 The ability to implement hierarchical deterministic wallets depends on the ability to create and derive hierarchical
6 deterministic extended keys. At a high level, this package provides support for those hierarchical deterministic
7 extended keys by providing an ExtendedKey type and supporting functions. Each extended key can either be a private or
8 public extended key which itself is capable of deriving a child extended key.
9 10 Determining the Extended Key Type
11 12 Whether an extended key is a private or public extended key can be determined with the IsPrivate function. Transaction
13 Signing Keys and Payment Addresses In order to create and sign transactions, or provide others with addresses to send
14 funds to, the underlying key and address material must be accessible. This package provides the ECPubKey, ECPrivKey, and
15 Address functions for this purpose.
16 17 The Master Node
18 19 As previously mentioned, the extended keys are hierarchical meaning they are used to form a tree. The root of that tree
20 is called the master node and this package provides the NewMaster function to create it from a cryptographically random
21 seed. The GenerateSeed function is provided as a convenient way to create a random seed for use with the NewMaster
22 function.
23 24 Deriving Children
25 26 Once you have created a tree root (or have deserialized an extended key as discussed later), the child extended keys can
27 be derived by using the Child function. The Child function supports deriving both normal (non-hardened) and hardened
28 child extended keys. In order to derive a hardened extended key, use the HardenedKeyStart constant + the hardened key
29 number as the index to the Child function. This provides the ability to cascade the keys into a tree and hence generate
30 the hierarchical deterministic key chains.
31 32 Normal vs Hardened Child Extended Keys
33 34 A private extended key can be used to derive both hardened and non-hardened (normal) child private and public extended
35 keys. A public extended key can only be used to derive non-hardened child public extended keys. As enumerated in BIP0032
36 "knowledge of the extended public key plus any non-hardened private key descending from it is equivalent to knowing the
37 extended private key (and thus every private and public key descending from it). This means that extended public keys
38 must be treated more carefully than regular public keys. It is also the reason for the existence of hardened keys, and
39 why they are used for the account level in the tree. This way, a leak of an account-specific (or below) private key
40 never risks compromising the master or other accounts."
41 42 Neutering a Private Extended Key
43 44 A private extended key can be converted to a new instance of the corresponding public extended key with the Neuter
45 function. The original extended key is not modified. A public extended key is still capable of deriving non-hardened
46 child public extended keys.
47 48 Serializing and Deserializing Extended Keys
49 50 Extended keys are serialized and deserialized with the String and NewKeyFromString functions. The serialized key is a
51 Base58-encoded string which looks like the following:
52 53 public key: xpub68Gmy5EdvgibQVfPdqkBBCHxA5htiqg55crXYuXoQRKfDBFA1WEjWgP6LHhwBZeNK1VTsfTFUHCdrfp1bgwQ9xv5ski8PX9rL2dZXvgGDnw
54 private key: xprv9uHRZZhk6KAJC1avXpDAp4MDc3sQKNxDiPvvkX8Br5ngLNv1TxvUxt4cV1rGL5hj6KCesnDYUhd7oWgT11eZG7XnxHrnYeSvkzY7d2bhkJ7
55 56 Network
57 58 Extended keys are much like normal Bitcoin addresses in that they have version bytes which tie them to a specific
59 network. The SetNet and IsForNet functions are provided to set and determinine which network an extended key is
60 associated with.
61 */
62 package hdkeychain
63