mirror of https://go.googlesource.com/go
30 lines
696 B
Go
30 lines
696 B
Go
// Copyright 2022 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build amd64 || arm64
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package elliptic
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import (
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"crypto/internal/nistec"
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"math/big"
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)
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func (c p256Curve) Inverse(k *big.Int) *big.Int {
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if k.Sign() < 0 {
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// This should never happen.
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k = new(big.Int).Neg(k)
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}
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if k.Cmp(c.params.N) >= 0 {
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// This should never happen.
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k = new(big.Int).Mod(k, c.params.N)
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}
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scalar := k.FillBytes(make([]byte, 32))
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inverse, err := nistec.P256OrdInverse(scalar)
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if err != nil {
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panic("crypto/elliptic: nistec rejected normalized scalar")
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}
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return new(big.Int).SetBytes(inverse)
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}
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