diff options
Diffstat (limited to 'vendor/golang.org/x/crypto/salsa20/salsa20.go')
-rw-r--r-- | vendor/golang.org/x/crypto/salsa20/salsa20.go | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/vendor/golang.org/x/crypto/salsa20/salsa20.go b/vendor/golang.org/x/crypto/salsa20/salsa20.go new file mode 100644 index 000000000..fde9846b6 --- /dev/null +++ b/vendor/golang.org/x/crypto/salsa20/salsa20.go @@ -0,0 +1,54 @@ +// 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 http://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 +an 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 http://cr.yp.to/snuffle/xsalsa-20081128.pdf. Simply +passing a 24-byte slice as the nonce triggers XSalsa20. +*/ +package salsa20 // import "golang.org/x/crypto/salsa20" + +// TODO(agl): implement XORKeyStream12 and XORKeyStream8 - the reduced round variants of Salsa20. + +import ( + "golang.org/x/crypto/salsa20/salsa" +) + +// XORKeyStream crypts bytes from in to out using the given key and nonce. In +// and out may be the same slice but otherwise should not overlap. Nonce must +// be either 8 or 24 bytes long. +func XORKeyStream(out, in []byte, nonce []byte, key *[32]byte) { + if len(out) < len(in) { + in = in[:len(out)] + } + + 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) +} |