1 files changed, 66 insertions, 0 deletions
diff --git a/libgo/go/crypto/rc4/rc4.go b/libgo/go/crypto/rc4/rc4.go
new file mode 100644
index 0000000000..65fd195f3d
--- /dev/null
+++ b/libgo/go/crypto/rc4/rc4.go
@@ -0,0 +1,66 @@
+// 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
+}