1 files changed, 80 insertions, 0 deletions
diff --git a/src/crypto/rc4/rc4.go b/src/crypto/rc4/rc4.go
new file mode 100644
index 0000000..f08da0e
--- /dev/null
+++ b/src/crypto/rc4/rc4.go
@@ -0,0 +1,80 @@
+// 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.
+//
+// RC4 is cryptographically broken and should not be used for secure
+// applications.
+package rc4
+
+import (
+	"crypto/internal/alias"
+	"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 and makes the Cipher unusable.
+//
+// Deprecated: Reset can't guarantee that the key will be entirely removed from
+// the process's memory.
+func (c *Cipher) Reset() {
+	for i := range c.s {
+		c.s[i] = 0
+	}
+	c.i, c.j = 0, 0
+}
+
+// XORKeyStream sets dst to the result of XORing src with the key stream.
+// Dst and src must overlap entirely or not at all.
+func (c *Cipher) XORKeyStream(dst, src []byte) {
+	if len(src) == 0 {
+		return
+	}
+	if alias.InexactOverlap(dst[:len(src)], src) {
+		panic("crypto/rc4: invalid buffer overlap")
+	}
+	i, j := c.i, c.j
+	_ = dst[len(src)-1]
+	dst = dst[:len(src)] // eliminate bounds check from loop
+	for k, v := range src {
+		i += 1
+		x := c.s[i]
+		j += uint8(x)
+		y := c.s[j]
+		c.s[i], c.s[j] = y, x
+		dst[k] = v ^ uint8(c.s[uint8(x+y)])
+	}
+	c.i, c.j = i, j
+}