1 files changed, 69 insertions, 0 deletions
diff --git a/src/crypto/rc4/rc4.go b/src/crypto/rc4/rc4.go
new file mode 100644
index 000000000..9acb681bf
--- /dev/null
+++ b/src/crypto/rc4/rc4.go
@@ -0,0 +1,69 @@
+// 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.
+
+// Package rc4 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 "strconv"
+
+// A Cipher is an instance of RC4 using a particular key.
+type Cipher struct {
+	s    [256]uint32
+	i, j uint8
+}
+
+type KeySizeError int
+
+func (k KeySizeError) Error() 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, 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] = uint32(i)
+	}
+	var j uint8 = 0
+	for i := 0; i < 256; i++ {
+		j += uint8(c.s[i]) + key[i%k]
+		c.s[i], c.s[j] = c.s[j], c.s[i]
+	}
+	return &c, nil
+}
+
+// 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
+}
+
+// xorKeyStreamGeneric 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.
+//
+// This is the pure Go version. rc4_{amd64,386,arm}* contain assembly
+// implementations. This is here for tests and to prevent bitrot.
+func (c *Cipher) xorKeyStreamGeneric(dst, src []byte) {
+	i, j := c.i, c.j
+	for k, v := range src {
+		i += 1
+		j += uint8(c.s[i])
+		c.s[i], c.s[j] = c.s[j], c.s[i]
+		dst[k] = v ^ uint8(c.s[uint8(c.s[i]+c.s[j])])
+	}
+	c.i, c.j = i, j
+}