0673eb5c80
This creates a new ExtendedKey child derivation method, ChildBIP32Std, which creates an ExtendedKey with leading zeroes retained for strict compliance with BIP32. This is not intended for Decred wallet use.
96 lines
4.6 KiB
Go
96 lines
4.6 KiB
Go
// Copyright (c) 2014 The btcsuite developers
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// Copyright (c) 2015-2021 The Decred developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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/*
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Package hdkeychain provides an API for Decred hierarchical deterministic
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extended keys (based on BIP0032).
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The ability to implement hierarchical deterministic wallets depends on the
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ability to create and derive hierarchical deterministic extended keys.
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At a high level, this package provides support for those hierarchical
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deterministic extended keys by providing an ExtendedKey type and supporting
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functions. Each extended key can either be a private or public extended key
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which itself is capable of deriving a child extended key.
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Determining the Extended Key Type
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Whether an extended key is a private or public extended key can be determined
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with the IsPrivate function.
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Transaction Signing Keys and Payment Addresses
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In order to create and sign transactions, or provide others with addresses to
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send funds to, the underlying key and address material must be accessible. This
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package provides the SerializedPubKey and SerializedPrivKey functions for this
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purpose. The caller may then create the desired address types.
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The Master Node
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As previously mentioned, the extended keys are hierarchical meaning they are
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used to form a tree. The root of that tree is called the master node and this
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package provides the NewMaster function to create it from a cryptographically
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random seed. The GenerateSeed function is provided as a convenient way to
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create a random seed for use with the NewMaster function.
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Deriving Children
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Once you have created a tree root (or have deserialized an extended key as
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discussed later), the child extended keys can be derived by using either the
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Child or ChildBIP32Std function. The difference is described in the following
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section. These functions support deriving both normal (non-hardened) and
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hardened child extended keys. In order to derive a hardened extended key, use
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the HardenedKeyStart constant + the hardened key number as the index to the
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Child function. This provides the ability to cascade the keys into a tree and
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hence generate the hierarchical deterministic key chains.
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BIP0032 Conformity
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The Child function derives extended keys with a modified scheme based on
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BIP0032, whereas ChildBIP32Std produces keys that strictly conform to the
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standard. Specifically, the Decred variation strips leading zeros of a private
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key, causing subsequent child keys to differ from the keys expected by standard
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BIP0032. The ChildBIP32Std method retains leading zeros, ensuring the child
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keys expected by BIP0032 are derived. The Child function must be used for
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Decred wallet key derivation for legacy reasons.
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Normal vs Hardened Child Extended Keys
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A private extended key can be used to derive both hardened and non-hardened
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(normal) child private and public extended keys. A public extended key can only
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be used to derive non-hardened child public extended keys. As enumerated in
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BIP0032 "knowledge of the extended public key plus any non-hardened private key
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descending from it is equivalent to knowing the extended private key (and thus
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every private and public key descending from it). This means that extended
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public keys must be treated more carefully than regular public keys. It is also
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the reason for the existence of hardened keys, and why they are used for the
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account level in the tree. This way, a leak of an account-specific (or below)
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private key never risks compromising the master or other accounts."
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Neutering a Private Extended Key
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A private extended key can be converted to a new instance of the corresponding
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public extended key with the Neuter function. The original extended key is not
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modified. A public extended key is still capable of deriving non-hardened child
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public extended keys.
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Serializing and Deserializing Extended Keys
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Extended keys are serialized and deserialized with the String and
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NewKeyFromString functions. The serialized key is a Base58-encoded string which
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looks like the following:
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public key: dpubZCGVaKZBiMo7pMgLaZm1qmchjWenTeVcUdFQkTNsFGFEA6xs4EW8PKiqYqP7HBAitt9Hw16VQkQ1tjsZQSHNWFc6bEK6bLqrbco24FzBTY4
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private key: dprv3kUQDBztdyjKuwnaL3hfKYpT7W6X2huYH5d61YSWFBebSYwEBHAXJkCpQ7rvMAxPzKqxVCGLvBqWvGxXjAyMJsV1XwKkfnQCM9KctC8k8bk
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Network
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Extended keys are much like normal Decred addresses in that they have version
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bytes which tie them to a specific network. The network that an extended key is
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associated with is specified when creating and decoding the key. In the case of
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decoding, an error will be returned if a given encoded extended key is not for
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the specified network.
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*/
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package hdkeychain
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