60 lines
1.9 KiB
Go
60 lines
1.9 KiB
Go
// Copyright (c) 2015 The btcsuite developers
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//
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// Permission to use, copy, modify, and distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice appear in all copies.
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//
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// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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// Go >= 1.5 optimizes range-based zeroing of the form:
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//
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// for i := range slice {
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// slice[i] = 0
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// }
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//
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// to an optimized implementation using a Duff's device, but older versions
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// do not and benefit from this custom implementation.
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//
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// +build go1.3 go1.4
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package zero
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import (
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"math/big"
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)
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// Bytes sets all bytes in the passed slice to zero. This is used to
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// explicitly clear private key material from memory.
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//
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// In general, prefer to use the fixed-sized zeroing functions (Bytea*)
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// when zeroing bytes as they are much more efficient than the variable
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// sized zeroing func Bytes.
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func Bytes(b []byte) {
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z := [32]byte{}
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n := uint(copy(b, z[:]))
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for n < uint(len(b)) {
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copy(b[n:], b[:n])
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n <<= 1
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}
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}
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// BigInt sets all bytes in the passed big int to zero and then sets the
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// value to 0. This differs from simply setting the value in that it
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// specifically clears the underlying bytes whereas simply setting the value
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// does not. This is mostly useful to forcefully clear private keys.
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func BigInt(x *big.Int) {
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b := x.Bits()
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z := [16]big.Word{}
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n := uint(copy(b, z[:]))
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for n < uint(len(b)) {
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copy(b[n:], b[:n])
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n <<= 1
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}
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x.SetInt64(0)
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}
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