Filippo Valsorda
a6a393ffd6
Also, remove the legacy import annotations. Fixes golang/go#68147 Change-Id: Ibfcc9322f27224c0ba92ea42cd56912a7d8783fd Reviewed-on: https://go-review.googlesource.com/c/crypto/+/594256 Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Auto-Submit: Filippo Valsorda <filippo@golang.org> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Roland Shoemaker <roland@golang.org>
59 lines
2.0 KiB
Go
59 lines
2.0 KiB
Go
// Copyright 2012 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
/*
|
|
Package salsa20 implements the Salsa20 stream cipher as specified in https://cr.yp.to/snuffle/spec.pdf.
|
|
|
|
Salsa20 differs from many other stream ciphers in that it is message orientated
|
|
rather than byte orientated. Keystream blocks are not preserved between calls,
|
|
therefore each side must encrypt/decrypt data with the same segmentation.
|
|
|
|
Another aspect of this difference is that part of the counter is exposed as
|
|
a nonce in each call. Encrypting two different messages with the same (key,
|
|
nonce) pair leads to trivial plaintext recovery. This is analogous to
|
|
encrypting two different messages with the same key with a traditional stream
|
|
cipher.
|
|
|
|
This package also implements XSalsa20: a version of Salsa20 with a 24-byte
|
|
nonce as specified in https://cr.yp.to/snuffle/xsalsa-20081128.pdf. Simply
|
|
passing a 24-byte slice as the nonce triggers XSalsa20.
|
|
*/
|
|
package salsa20
|
|
|
|
// TODO(agl): implement XORKeyStream12 and XORKeyStream8 - the reduced round variants of Salsa20.
|
|
|
|
import (
|
|
"golang.org/x/crypto/internal/alias"
|
|
"golang.org/x/crypto/salsa20/salsa"
|
|
)
|
|
|
|
// XORKeyStream crypts bytes from in to out using the given key and nonce.
|
|
// In and out must overlap entirely or not at all. Nonce must
|
|
// be either 8 or 24 bytes long.
|
|
func XORKeyStream(out, in []byte, nonce []byte, key *[32]byte) {
|
|
if len(out) < len(in) {
|
|
panic("salsa20: output smaller than input")
|
|
}
|
|
if alias.InexactOverlap(out[:len(in)], in) {
|
|
panic("salsa20: invalid buffer overlap")
|
|
}
|
|
|
|
var subNonce [16]byte
|
|
|
|
if len(nonce) == 24 {
|
|
var subKey [32]byte
|
|
var hNonce [16]byte
|
|
copy(hNonce[:], nonce[:16])
|
|
salsa.HSalsa20(&subKey, &hNonce, key, &salsa.Sigma)
|
|
copy(subNonce[:], nonce[16:])
|
|
key = &subKey
|
|
} else if len(nonce) == 8 {
|
|
copy(subNonce[:], nonce[:])
|
|
} else {
|
|
panic("salsa20: nonce must be 8 or 24 bytes")
|
|
}
|
|
|
|
salsa.XORKeyStream(out, in, &subNonce, key)
|
|
}
|