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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
commit554fd8c5195424bdbcabf5de30fdc183aba391bd (patch)
tree976dc5ab7fddf506dadce60ae936f43f58787092 /libgo/go/crypto/rc4/rc4.go
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Diffstat (limited to 'libgo/go/crypto/rc4/rc4.go')
-rw-r--r--libgo/go/crypto/rc4/rc4.go66
1 files changed, 66 insertions, 0 deletions
diff --git a/libgo/go/crypto/rc4/rc4.go b/libgo/go/crypto/rc4/rc4.go
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+++ b/libgo/go/crypto/rc4/rc4.go
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+// Copyright 2009 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.
+
+// This package implements RC4 encryption, as defined in Bruce Schneier's
+// Applied Cryptography.
+package rc4
+
+// BUG(agl): RC4 is in common use but has design weaknesses that make
+// it a poor choice for new protocols.
+
+import (
+ "os"
+ "strconv"
+)
+
+// A Cipher is an instance of RC4 using a particular key.
+type Cipher struct {
+ s [256]byte
+ i, j uint8
+}
+
+type KeySizeError int
+
+func (k KeySizeError) String() string {
+ return "crypto/rc4: invalid key size " + strconv.Itoa(int(k))
+}
+
+// NewCipher creates and returns a new Cipher. The key argument should be the
+// RC4 key, at least 1 byte and at most 256 bytes.
+func NewCipher(key []byte) (*Cipher, os.Error) {
+ k := len(key)
+ if k < 1 || k > 256 {
+ return nil, KeySizeError(k)
+ }
+ var c Cipher
+ for i := 0; i < 256; i++ {
+ c.s[i] = uint8(i)
+ }
+ var j uint8 = 0
+ for i := 0; i < 256; i++ {
+ j += c.s[i] + key[i%k]
+ c.s[i], c.s[j] = c.s[j], c.s[i]
+ }
+ return &c, nil
+}
+
+// XORKeyStream sets dst to the result of XORing src with the key stream.
+// Dst and src may be the same slice but otherwise should not overlap.
+func (c *Cipher) XORKeyStream(dst, src []byte) {
+ for i := range src {
+ c.i += 1
+ c.j += c.s[c.i]
+ c.s[c.i], c.s[c.j] = c.s[c.j], c.s[c.i]
+ dst[i] = src[i] ^ c.s[c.s[c.i]+c.s[c.j]]
+ }
+}
+
+// Reset zeros the key data so that it will no longer appear in the
+// process's memory.
+func (c *Cipher) Reset() {
+ for i := range c.s {
+ c.s[i] = 0
+ }
+ c.i, c.j = 0, 0
+}