doc.go

/*
Package hdkeychain provides an API for bitcoin hierarchical deterministic extended keys (BIP0032).

Overview

The ability to implement hierarchical deterministic wallets depends on the ability to create and derive hierarchical deterministic extended keys. At a high level, this package provides support for those hierarchical deterministic extended keys by providing an ExtendedKey type and supporting functions.  Each extended key can either be a private or public extended key which itself is capable of deriving a child extended key.

Determining the Extended Key Type

Whether an extended key is a private or public extended key can be determined with the IsPrivate function. Transaction Signing Keys and Payment Addresses In order to create and sign transactions, or provide others with addresses to send funds to, the underlying key and address material must be accessible.  This
package provides the ECPubKey, ECPrivKey, and Address functions for this purpose.

The Master Node

As previously mentioned, the extended keys are hierarchical meaning they are used to form a tree.  The root of that tree is called the master node and this package provides the NewMaster function to create it from a cryptographically random seed.  The GenerateSeed function is provided as a convenient way to create a random seed for use with the NewMaster function.

Deriving Children

Once you have created a tree root (or have deserialized an extended key as discussed later), the child extended keys can be derived by using the Child function.  The Child function supports deriving both normal (non-hardened) and hardened child extended keys.  In order to derive a hardened extended key, use the  HardenedKeyStart constant + the hardened key number as the index to the Child function.  This provides the ability to cascade the keys into a tree and hence generate the hierarchical deterministic key chains.

Normal vs Hardened Child Extended Keys

A private extended key can be used to derive both hardened and non-hardened (normal) child private and public extended keys.  A public extended key can only be used to derive non-hardened child public extended keys.  As enumerated in BIP0032 "knowledge of the extended public key plus any non-hardened private key descending from it is equivalent to knowing the extended private key (and thus every private and public key descending from it).  This means that extended public keys must be treated more carefully than regular public keys. It is also the reason for the existence of hardened keys, and why they are used for the account level in the tree. This way, a leak of an account-specific (or below) private key never risks compromising the master or other accounts."

Neutering a Private Extended Key

A private extended key can be converted to a new instance of the corresponding public extended key with the Neuter function.  The original extended key is not modified.  A public extended key is still capable of deriving non-hardened child public extended keys.

Serializing and Deserializing Extended Keys

Extended keys are serialized and deserialized with the String and NewKeyFromString functions.  The serialized key is a Base58-encoded string which looks like the following:

	public key:   xpub68Gmy5EdvgibQVfPdqkBBCHxA5htiqg55crXYuXoQRKfDBFA1WEjWgP6LHhwBZeNK1VTsfTFUHCdrfp1bgwQ9xv5ski8PX9rL2dZXvgGDnw
	private key:  xprv9uHRZZhk6KAJC1avXpDAp4MDc3sQKNxDiPvvkX8Br5ngLNv1TxvUxt4cV1rGL5hj6KCesnDYUhd7oWgT11eZG7XnxHrnYeSvkzY7d2bhkJ7

Network

Extended keys are much like normal Bitcoin addresses in that they have version bytes which tie them to a specific network.  The SetNet and IsForNet functions are provided to set and determinine which network an extended key is associated with.
*/
package hdkeychain