84 lines
3.8 KiB
Go
84 lines
3.8 KiB
Go
// Copyright (c) 2014 The btcsuite 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 bitcoin hierarchical deterministic
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extended keys (BIP0032).
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Overview
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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 ECPubKey, ECPrivKey, and Address functions for this
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purpose.
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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 the Derive
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function. The Derive function supports 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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Derive 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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Normal vs Hardened Derived 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: xpub68Gmy5EdvgibQVfPdqkBBCHxA5htiqg55crXYuXoQRKfDBFA1WEjWgP6LHhwBZeNK1VTsfTFUHCdrfp1bgwQ9xv5ski8PX9rL2dZXvgGDnw
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private key: xprv9uHRZZhk6KAJC1avXpDAp4MDc3sQKNxDiPvvkX8Br5ngLNv1TxvUxt4cV1rGL5hj6KCesnDYUhd7oWgT11eZG7XnxHrnYeSvkzY7d2bhkJ7
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Network
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Extended keys are much like normal Bitcoin addresses in that they have version
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bytes which tie them to a specific network. The SetNet and IsForNet functions
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are provided to set and determinine which network an extended key is associated
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with.
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*/
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package hdkeychain
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