diff --git a/src/pkg/Make.deps b/src/pkg/Make.deps
index 70992cc7f2..7ced9fa2d9 100644
--- a/src/pkg/Make.deps
+++ b/src/pkg/Make.deps
@@ -15,6 +15,7 @@ crypto/aes.install: os.install strconv.install
 crypto/block.install: fmt.install io.install os.install strconv.install
 crypto/hmac.install: crypto/md5.install crypto/sha1.install hash.install os.install
 crypto/md5.install: hash.install os.install
+crypto/rc4.install: os.install strconv.install
 crypto/sha1.install: hash.install os.install
 datafmt.install: bytes.install container/vector.install fmt.install go/scanner.install go/token.install io.install os.install reflect.install runtime.install strconv.install strings.install
 debug/binary.install: io.install math.install os.install reflect.install
@@ -31,7 +32,7 @@ fmt.install: io.install os.install reflect.install strconv.install utf8.install
 go/ast.install: go/token.install unicode.install utf8.install
 go/doc.install: container/vector.install go/ast.install go/token.install io.install once.install regexp.install sort.install strings.install template.install
 go/parser.install: bytes.install container/vector.install fmt.install go/ast.install go/scanner.install go/token.install io.install os.install path.install strings.install
-go/printer.install: bytes.install container/vector.install fmt.install go/ast.install go/token.install io.install os.install reflect.install strings.install tabwriter.install
+go/printer.install: bytes.install container/vector.install fmt.install go/ast.install go/token.install io.install os.install reflect.install runtime.install strings.install tabwriter.install
 go/scanner.install: bytes.install container/vector.install fmt.install go/token.install io.install os.install sort.install strconv.install unicode.install utf8.install
 go/token.install: fmt.install strconv.install
 gob.install: bytes.install fmt.install io.install math.install os.install reflect.install sync.install
diff --git a/src/pkg/Makefile b/src/pkg/Makefile
index c368709df9..ad2b7828d2 100644
--- a/src/pkg/Makefile
+++ b/src/pkg/Makefile
@@ -29,6 +29,7 @@ DIRS=\
 	crypto/block\
 	crypto/hmac\
 	crypto/md5\
+	crypto/rc4\
 	crypto/sha1\
 	datafmt\
 	debug/binary\
diff --git a/src/pkg/crypto/rc4/Makefile b/src/pkg/crypto/rc4/Makefile
new file mode 100644
index 0000000000..5c7e67fa0c
--- /dev/null
+++ b/src/pkg/crypto/rc4/Makefile
@@ -0,0 +1,11 @@
+# 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.
+
+include $(GOROOT)/src/Make.$(GOARCH)
+
+TARG=crypto/rc4
+GOFILES=\
+	rc4.go\
+
+include $(GOROOT)/src/Make.pkg
diff --git a/src/pkg/crypto/rc4/rc4.go b/src/pkg/crypto/rc4/rc4.go
new file mode 100644
index 0000000000..a93784e622
--- /dev/null
+++ b/src/pkg/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 will XOR each byte of the given buffer with a byte of the
+// generated keystream.
+func (c *Cipher) XORKeyStream(buf []byte) {
+	for i := range buf {
+		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];
+		buf[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;
+}
diff --git a/src/pkg/crypto/rc4/rc4_test.go b/src/pkg/crypto/rc4/rc4_test.go
new file mode 100644
index 0000000000..e0ca4a4ae6
--- /dev/null
+++ b/src/pkg/crypto/rc4/rc4_test.go
@@ -0,0 +1,59 @@
+// 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
+
+import (
+	"testing";
+)
+
+type rc4Test struct {
+	key, keystream []byte;
+}
+
+var golden = []rc4Test{
+	// Test vectors from the original cypherpunk posting of ARC4:
+	//   http://groups.google.com/group/sci.crypt/msg/10a300c9d21afca0?pli=1
+	rc4Test{
+		[]byte{0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef},
+		[]byte{0x74, 0x94, 0xc2, 0xe7, 0x10, 0x4b, 0x08, 0x79},
+	},
+	rc4Test{
+		[]byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
+		[]byte{0xde, 0x18, 0x89, 0x41, 0xa3, 0x37, 0x5d, 0x3a},
+	},
+	rc4Test{
+		[]byte{0xef, 0x01, 0x23, 0x45},
+		[]byte{0xd6, 0xa1, 0x41, 0xa7, 0xec, 0x3c, 0x38, 0xdf, 0xbd, 0x61},
+	},
+
+	// Test vectors from the Wikipedia page: http://en.wikipedia.org/wiki/RC4
+	rc4Test{
+		[]byte{0x4b, 0x65, 0x79},
+		[]byte{0xeb, 0x9f, 0x77, 0x81, 0xb7, 0x34, 0xca, 0x72, 0xa7, 0x19},
+	},
+	rc4Test{
+		[]byte{0x57, 0x69, 0x6b, 0x69},
+		[]byte{0x60, 0x44, 0xdb, 0x6d, 0x41, 0xb7},
+	},
+}
+
+func TestGolden(t *testing.T) {
+	for i := 0; i < len(golden); i++ {
+		g := golden[i];
+		c, err := NewCipher(g.key);
+		if err != nil {
+			t.Errorf("Failed to create cipher at golden index %d", i);
+			return;
+		}
+		keystream := make([]byte, len(g.keystream));
+		c.XORKeyStream(keystream);
+		for j, v := range keystream {
+			if g.keystream[j] != v {
+				t.Errorf("Failed at golden index %d", i);
+				break;
+			}
+		}
+	}
+}