46 lines
2.1 KiB
Go
46 lines
2.1 KiB
Go
// Copyright (c) 2013-2021 The btcsuite developers
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// Copyright (c) 2015-2021 The Decred developers
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package btcec
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import (
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secp "github.com/decred/dcrd/dcrec/secp256k1/v4"
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)
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// ModNScalar implements optimized 256-bit constant-time fixed-precision
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// arithmetic over the secp256k1 group order. This means all arithmetic is
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// performed modulo:
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//
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// 0xfffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141
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//
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// It only implements the arithmetic needed for elliptic curve operations,
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// however, the operations that are not implemented can typically be worked
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// around if absolutely needed. For example, subtraction can be performed by
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// adding the negation.
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//
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// Should it be absolutely necessary, conversion to the standard library
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// math/big.Int can be accomplished by using the Bytes method, slicing the
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// resulting fixed-size array, and feeding it to big.Int.SetBytes. However,
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// that should typically be avoided when possible as conversion to big.Ints
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// requires allocations, is not constant time, and is slower when working modulo
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// the group order.
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type ModNScalar = secp.ModNScalar
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// NonceRFC6979 generates a nonce deterministically according to RFC 6979 using
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// HMAC-SHA256 for the hashing function. It takes a 32-byte hash as an input
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// and returns a 32-byte nonce to be used for deterministic signing. The extra
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// and version arguments are optional, but allow additional data to be added to
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// the input of the HMAC. When provided, the extra data must be 32-bytes and
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// version must be 16 bytes or they will be ignored.
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//
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// Finally, the extraIterations parameter provides a method to produce a stream
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// of deterministic nonces to ensure the signing code is able to produce a nonce
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// that results in a valid signature in the extremely unlikely event the
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// original nonce produced results in an invalid signature (e.g. R == 0).
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// Signing code should start with 0 and increment it if necessary.
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func NonceRFC6979(privKey []byte, hash []byte, extra []byte, version []byte,
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extraIterations uint32) *ModNScalar {
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return secp.NonceRFC6979(privKey, hash, extra, version, extraIterations)
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}
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