diff --git a/src/lib/crypto/block/cfb.go b/src/lib/crypto/block/cfb.go
index 827a55ee1c4..5c4c09a1b1f 100644
--- a/src/lib/crypto/block/cfb.go
+++ b/src/lib/crypto/block/cfb.go
@@ -27,7 +27,7 @@ type cfbCipher struct {
 
 func newCFB(c Cipher, s int, iv []byte) *cfbCipher {
 	if s == 0 || s % 8 != 0 {
-		panicln("invalid CFB mode", s);
+		panicln("crypto/block: invalid CFB mode", s);
 	}
 	b := c.BlockSize();
 	x := new(cfbCipher);
diff --git a/src/lib/crypto/block/cipher.go b/src/lib/crypto/block/cipher.go
index 8bff1b87820..7ea035db9a6 100644
--- a/src/lib/crypto/block/cipher.go
+++ b/src/lib/crypto/block/cipher.go
@@ -8,6 +8,8 @@
 // and NIST Special Publication 800-38A.
 package block
 
+import "io";
+
 // A Cipher represents an implementation of block cipher
 // using a given key.  It provides the capability to encrypt
 // or decrypt individual blocks.  The mode implementations
@@ -25,6 +27,20 @@ type Cipher interface {
 	Decrypt(src, dst []byte);
 }
 
+// TODO(rsc): Digest belongs elsewhere.
+
+// A Digest is an implementation of a message digest algorithm.
+// Write data to it and then call Sum to retreive the digest.
+// Calling Reset resets the internal state, as though no data has
+// been written.
+type Digest interface {
+	io.Writer;
+	Sum() []byte;
+	Reset();
+}
+
+
+
 // Utility routines
 
 func shift1(src, dst []byte) byte {
diff --git a/src/lib/crypto/block/cmac.go b/src/lib/crypto/block/cmac.go
new file mode 100644
index 00000000000..40697cabdcd
--- /dev/null
+++ b/src/lib/crypto/block/cmac.go
@@ -0,0 +1,105 @@
+// 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.
+
+// CMAC message authentication code, defined in
+// NIST Special Publication SP 800-38B.
+
+package block
+
+import (
+	"crypto/block";
+	"io";
+	"os";
+)
+
+const (
+	// minimal irreducible polynomial of degree b
+	r64 = 0x1b;
+	r128 = 0x87;
+)
+
+type cmac struct {
+	k1, k2, ci, digest []byte;
+	p int;	// position in ci
+	c Cipher;
+}
+
+// TODO(rsc): Should this return an error instead of panic?
+
+// NewCMAC returns a new instance of a CMAC message authentication code
+// digest using the given Cipher.
+func NewCMAC(c Cipher) Digest {
+	var r byte;
+	n := c.BlockSize();
+	switch n {
+	case 64/8:
+		r = r64;
+	case 128/8:
+		r = r128;
+	default:
+		panic("crypto/block: NewCMAC: invalid cipher block size", n);
+	}
+
+	d := new(cmac);
+	d.c = c;
+	d.k1 = make([]byte, n);
+	d.k2 = make([]byte, n);
+	d.ci = make([]byte, n);
+	d.digest = make([]byte, n);
+
+	// Subkey generation, p. 7
+	c.Encrypt(d.k1, d.k1);
+	if shift1(d.k1, d.k1) != 0 {
+		d.k1[n-1] ^= r;
+	}
+	if shift1(d.k1, d.k2) != 0 {
+		d.k2[n-1] ^= r;
+	}
+
+	return d;
+}
+
+// Reset clears the digest state, starting a new digest.
+func (d *cmac) Reset() {
+	for i := range d.ci {
+		d.ci[i] = 0;
+	}
+	d.p = 0;
+}
+
+// Write adds the given data to the digest state.
+func (d *cmac) Write(p []byte) (n int, err os.Error) {
+	// Xor input into ci.
+	for i, c := range p {
+		// If ci is full, encrypt and start over.
+		if d.p >= len(d.ci) {
+			d.c.Encrypt(d.ci, d.ci);
+			d.p = 0;
+		}
+		d.ci[d.p] ^= c;
+		d.p++;
+	}
+	return len(p), nil;
+}
+
+// Sum returns the CMAC digest, one cipher block in length,
+// of the data written with Write.
+func (d *cmac) Sum() []byte {
+	// Finish last block, mix in key, encrypt.
+	// Don't edit ci, in case caller wants
+	// to keep digesting after call to Sum.
+	k := d.k1;
+	if d.p < len(d.digest) {
+		k = d.k2;
+	}
+	for i := 0; i < len(d.ci); i++ {
+		d.digest[i] = d.ci[i] ^ k[i];
+	}
+	if d.p < len(d.digest) {
+		d.digest[d.p] ^= 0x80;
+	}
+	d.c.Encrypt(d.digest, d.digest);
+	return d.digest;
+}
+
diff --git a/src/lib/crypto/block/cmac_aes_test.go b/src/lib/crypto/block/cmac_aes_test.go
new file mode 100644
index 00000000000..9284ac40a01
--- /dev/null
+++ b/src/lib/crypto/block/cmac_aes_test.go
@@ -0,0 +1,165 @@
+// 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.
+
+// CMAC test vectors.  See NIST SP 800-38B, Appendix D.
+
+package block
+
+// gobuild: $GC ecb_aes_test.go
+
+import (
+	"crypto/aes";
+	"crypto/block";
+	"testing";
+
+	"./ecb_aes_test";
+)
+
+type cmacAESTest struct {
+	key []byte;
+	in []byte;
+	digest []byte;
+}
+
+var cmacAESTests = []cmacAESTest {
+	cmacAESTest {
+		commonKey128,
+		nil,
+		[]byte {
+			0xbb, 0x1d, 0x69, 0x29, 0xe9, 0x59, 0x37, 0x28, 0x7f, 0xa3, 0x7d, 0x12, 0x9b, 0x75, 0x67, 0x46,
+ 		}
+ 	},
+ 	cmacAESTest {
+ 		commonKey128,
+ 		[]byte {
+			0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
+		},
+		[]byte {
+			0x07, 0x0a, 0x16, 0xb4, 0x6b, 0x4d, 0x41, 0x44, 0xf7, 0x9b, 0xdd, 0x9d, 0xd0, 0x4a, 0x28, 0x7c,
+		}
+	},
+	cmacAESTest {
+		commonKey128,
+		[]byte {
+			0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
+			0xae, 0x2d, 0x8a, 0x57, 0x1e, 0x03, 0xac, 0x9c, 0x9e, 0xb7, 0x6f, 0xac, 0x45, 0xaf, 0x8e, 0x51,
+			0x30, 0xc8, 0x1c, 0x46, 0xa3, 0x5c, 0xe4, 0x11,
+		},
+		[]byte {
+			0xdf, 0xa6, 0x67, 0x47, 0xde, 0x9a, 0xe6, 0x30, 0x30, 0xca, 0x32, 0x61, 0x14, 0x97, 0xc8, 0x27,
+		}
+	},
+	cmacAESTest {
+		commonKey128,
+		[]byte {
+			0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
+			0xae, 0x2d, 0x8a, 0x57, 0x1e, 0x03, 0xac, 0x9c, 0x9e, 0xb7, 0x6f, 0xac, 0x45, 0xaf, 0x8e, 0x51,
+			0x30, 0xc8, 0x1c, 0x46, 0xa3, 0x5c, 0xe4, 0x11, 0xe5, 0xfb, 0xc1, 0x19, 0x1a, 0x0a, 0x52, 0xef,
+			0xf6, 0x9f, 0x24, 0x45, 0xdf, 0x4f, 0x9b, 0x17, 0xad, 0x2b, 0x41, 0x7b, 0xe6, 0x6c, 0x37, 0x10,
+		},
+		[]byte {
+			0x51, 0xf0, 0xbe, 0xbf, 0x7e, 0x3b, 0x9d, 0x92, 0xfc, 0x49, 0x74, 0x17, 0x79, 0x36, 0x3c, 0xfe,
+		}
+	},
+	cmacAESTest {
+		commonKey192,
+		nil,
+		[]byte {
+			0xd1, 0x7d, 0xdf, 0x46, 0xad, 0xaa, 0xcd, 0xe5, 0x31, 0xca, 0xc4, 0x83, 0xde, 0x7a, 0x93, 0x67,
+ 		}
+ 	},
+ 	cmacAESTest {
+ 		commonKey192,
+ 		[]byte {
+			0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
+		},
+		[]byte {
+			0x9e, 0x99, 0xa7, 0xbf, 0x31, 0xe7, 0x10, 0x90, 0x06, 0x62, 0xf6, 0x5e, 0x61, 0x7c, 0x51, 0x84,
+ 		}
+ 	},
+ 	cmacAESTest {
+ 		commonKey192,
+ 		[]byte {
+			0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
+			0xae, 0x2d, 0x8a, 0x57, 0x1e, 0x03, 0xac, 0x9c, 0x9e, 0xb7, 0x6f, 0xac, 0x45, 0xaf, 0x8e, 0x51,
+			0x30, 0xc8, 0x1c, 0x46, 0xa3, 0x5c, 0xe4, 0x11,
+		},
+		[]byte {
+			0x8a, 0x1d, 0xe5, 0xbe, 0x2e, 0xb3, 0x1a, 0xad, 0x08, 0x9a, 0x82, 0xe6, 0xee, 0x90, 0x8b, 0x0e,
+		}
+	},
+	cmacAESTest {
+		commonKey192,
+		[]byte {
+			0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
+			0xae, 0x2d, 0x8a, 0x57, 0x1e, 0x03, 0xac, 0x9c, 0x9e, 0xb7, 0x6f, 0xac, 0x45, 0xaf, 0x8e, 0x51,
+			0x30, 0xc8, 0x1c, 0x46, 0xa3, 0x5c, 0xe4, 0x11, 0xe5, 0xfb, 0xc1, 0x19, 0x1a, 0x0a, 0x52, 0xef,
+			0xf6, 0x9f, 0x24, 0x45, 0xdf, 0x4f, 0x9b, 0x17, 0xad, 0x2b, 0x41, 0x7b, 0xe6, 0x6c, 0x37, 0x10,
+		},
+		[]byte {
+			0xa1, 0xd5, 0xdf, 0x0e, 0xed, 0x79, 0x0f, 0x79, 0x4d, 0x77, 0x58, 0x96, 0x59, 0xf3, 0x9a, 0x11,
+		}
+	},
+	cmacAESTest {
+		commonKey256,
+		nil,
+		[]byte {
+			0x02, 0x89, 0x62, 0xf6, 0x1b, 0x7b, 0xf8, 0x9e, 0xfc, 0x6b, 0x55, 0x1f, 0x46, 0x67, 0xd9, 0x83,
+ 		}
+ 	},
+ 	cmacAESTest {
+ 		commonKey256,
+ 		[]byte {
+			0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
+		},
+		[]byte {
+			0x28, 0xa7, 0x02, 0x3f, 0x45, 0x2e, 0x8f, 0x82, 0xbd, 0x4b, 0xf2, 0x8d, 0x8c, 0x37, 0xc3, 0x5c,
+ 		}
+ 	},
+ 	cmacAESTest {
+ 		commonKey256,
+ 		[]byte {
+			0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
+			0xae, 0x2d, 0x8a, 0x57, 0x1e, 0x03, 0xac, 0x9c, 0x9e, 0xb7, 0x6f, 0xac, 0x45, 0xaf, 0x8e, 0x51,
+			0x30, 0xc8, 0x1c, 0x46, 0xa3, 0x5c, 0xe4, 0x11,
+		},
+		[]byte {
+			0xaa, 0xf3, 0xd8, 0xf1, 0xde, 0x56, 0x40, 0xc2, 0x32, 0xf5, 0xb1, 0x69, 0xb9, 0xc9, 0x11, 0xe6,
+ 		}
+ 	},
+ 	cmacAESTest {
+ 		commonKey256,
+ 		[]byte {
+			0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
+			0xae, 0x2d, 0x8a, 0x57, 0x1e, 0x03, 0xac, 0x9c, 0x9e, 0xb7, 0x6f, 0xac, 0x45, 0xaf, 0x8e, 0x51,
+			0x30, 0xc8, 0x1c, 0x46, 0xa3, 0x5c, 0xe4, 0x11, 0xe5, 0xfb, 0xc1, 0x19, 0x1a, 0x0a, 0x52, 0xef,
+			0xf6, 0x9f, 0x24, 0x45, 0xdf, 0x4f, 0x9b, 0x17, 0xad, 0x2b, 0x41, 0x7b, 0xe6, 0x6c, 0x37, 0x10,
+		},
+		[]byte {
+			0xe1, 0x99, 0x21, 0x90, 0x54, 0x9f, 0x6e, 0xd5, 0x69, 0x6a, 0x2c, 0x05, 0x6c, 0x31, 0x54, 0x10,
+		}
+	}
+}
+
+func TestCMAC_AES(t *testing.T) {
+	for i, tt := range cmacAESTests {
+		c, err := aes.NewCipher(tt.key);
+		if err != nil {
+			t.Errorf("test %d: NewCipher: %s", i, err);
+			continue;
+		}
+		d := NewCMAC(c);
+		n, err := d.Write(tt.in);
+		if err != nil || n != len(tt.in) {
+			t.Errorf("test %d: Write %d: %d, %s", i, len(tt.in), n, err);
+			continue;
+		}
+		sum := d.Sum();
+		if !same(sum, tt.digest) {
+			x := d.(*cmac);
+			t.Errorf("test %d: digest mismatch\n\twant %x\n\thave %x\n\tk1 %x\n\tk2 %x", i, tt.digest, sum, x.k1, x.k2);
+			continue;
+		}
+	}
+}
diff --git a/src/lib/crypto/block/ctr.go b/src/lib/crypto/block/ctr.go
index 98fd1939229..eecb615ad10 100644
--- a/src/lib/crypto/block/ctr.go
+++ b/src/lib/crypto/block/ctr.go
@@ -53,7 +53,7 @@ func (x *ctrStream) Next() []byte {
 // a CTR reader applied to an encrypted stream produces a decrypted
 // stream and vice versa.
 func NewCTRReader(c Cipher, iv []byte, r io.Reader) io.Reader {
-	return NewXorReader(newCTRStream(c, iv), r);
+	return newXorReader(newCTRStream(c, iv), r);
 }
 
 // NewCTRWriter returns a writer that encrypts (or decrypts) data using c
@@ -64,6 +64,6 @@ func NewCTRReader(c Cipher, iv []byte, r io.Reader) io.Reader {
 // a CTR writer applied to an decrypted stream produces an encrypted
 // stream and vice versa.
 func NewCTRWriter(c Cipher, iv []byte, w io.Writer) io.Writer {
-	return NewXorWriter(newCTRStream(c, iv), w);
+	return newXorWriter(newCTRStream(c, iv), w);
 }
 
diff --git a/src/lib/crypto/block/eax.go b/src/lib/crypto/block/eax.go
new file mode 100644
index 00000000000..7e1d7475cbf
--- /dev/null
+++ b/src/lib/crypto/block/eax.go
@@ -0,0 +1,254 @@
+// 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.
+
+// EAX mode, not a NIST standard (yet).
+// EAX provides encryption and authentication.
+// EAX targets the same uses as NIST's CCM mode,
+// but EAX adds the ability to run in streaming mode.
+
+// See
+// http://csrc.nist.gov/groups/ST/toolkit/BCM/documents/proposedmodes/eax/eax-spec.pdf
+// http://www.cs.ucdavis.edu/~rogaway/papers/eax.pdf
+// What those papers call OMAC is now called CMAC.
+
+package block
+
+import (
+	"crypto/block";
+	"fmt";
+	"io";
+	"os";
+)
+
+// An EAXTagError is returned when the message has failed to authenticate,
+// because the tag at the end of the message stream (Read) does not match
+// the tag computed from the message itself (Computed).
+type EAXTagError struct {
+	Read []byte;
+	Computed []byte;
+}
+
+func (e *EAXTagError) String() string {
+	return fmt.Sprintf("crypto/block: EAX tag mismatch: read %x but computed %x", e.Read, e.Computed);
+}
+
+func setupEAX(c Cipher, iv, hdr []byte, tagBytes int) (ctrIV, tag []byte, cmac Digest) {
+	n := len(iv);
+	if n != c.BlockSize() {
+		panicln("crypto/block: EAX: iv length", n, "!=", c.BlockSize());
+	}
+	buf := make([]byte, n);	// zeroed
+
+	// tag = CMAC(0 + iv) ^ CMAC(1 + hdr) ^ CMAC(2 + data)
+	cmac = NewCMAC(c);
+	cmac.Write(buf);	// 0
+	cmac.Write(iv);
+	sum := cmac.Sum();
+	ctrIV = copy(sum);
+	tag = copy(sum[0:tagBytes]);
+
+	cmac.Reset();
+	buf[n-1] = 1;
+	cmac.Write(buf);	// 1
+	cmac.Write(hdr);
+	sum = cmac.Sum();
+	for i := 0; i < tagBytes; i++ {
+		tag[i] ^= sum[i];
+	}
+
+	cmac.Reset();
+	buf[n-1] = 2;		// 2
+	cmac.Write(buf);
+
+	return;
+}
+
+func finishEAX(tag []byte, cmac Digest) {
+	// Finish CMAC #2 and xor into tag.
+	sum := cmac.Sum();
+	for i := range tag {
+		tag[i] ^= sum[i];
+	}
+}
+
+// Writer adapter.  Tees writes into both w and cmac.
+// Knows that cmac never returns write errors.
+type cmacWriter struct {
+	w io.Writer;
+	cmac Digest;
+}
+
+func (cw *cmacWriter) Write(p []byte) (n int, err os.Error) {
+	n, err = cw.w.Write(p);
+	cw.cmac.Write(p[0:n]);
+	return;
+}
+
+// An eaxEncrypter implements the EAX encryption mode.
+type eaxEncrypter struct {
+	ctr io.Writer;	// CTR encrypter
+	cw cmacWriter;	// CTR's output stream
+	tag []byte;
+}
+
+// NewEAXEncrypter creates and returns a new EAX encrypter
+// using the given cipher c, initialization vector iv, associated data hdr,
+// and tag length tagBytes.  The encrypter's Write method encrypts
+// the data it receives and writes that data to w.
+// The encrypter's Close method writes a final authenticating tag to w.
+func NewEAXEncrypter(c Cipher, iv []byte, hdr []byte, tagBytes int, w io.Writer) io.WriteCloser {
+	x := new(eaxEncrypter);
+
+	// Create new CTR instance writing to both
+	// w for encrypted output and cmac for digesting.
+	x.cw.w = w;
+	var ctrIV []byte;
+	ctrIV, x.tag, x.cw.cmac = setupEAX(c, iv, hdr, tagBytes);
+	x.ctr = NewCTRWriter(c, ctrIV, &x.cw);
+	return x;
+}
+
+func (x *eaxEncrypter) Write(p []byte) (n int, err os.Error) {
+	return x.ctr.Write(p);
+}
+
+func (x *eaxEncrypter) Close() os.Error {
+	x.ctr = nil;	// crash if Write is called again
+
+	// Write tag.
+	finishEAX(x.tag, x.cw.cmac);
+	n, err := x.cw.w.Write(x.tag);
+	if n != len(x.tag) && err == nil {
+		err = io.ErrShortWrite;
+	}
+
+	return err;
+}
+
+// Reader adapter.  Returns data read from r but hangs
+// on to the last len(tag) bytes for itself (returns EOF len(tag)
+// bytes early).  Also tees all data returned from Read into
+// the cmac digest.  The "don't return the last t bytes"
+// and the "tee into digest" functionality could be separated,
+// but the latter half is trivial.
+type cmacReader struct {
+	r io.Reader;
+	cmac Digest;
+	tag []byte;
+	tmp []byte;
+}
+
+func (cr *cmacReader) Read(p []byte) (n int, err os.Error) {
+	// TODO(rsc): Maybe fall back to simpler code if
+	// we recognize the underlying r as a ByteBuffer
+	// or ByteReader.  Then we can just take the last piece
+	// off at the start.
+
+	// First, read a tag-sized chunk.
+	// It's probably not the tag (unless there's no data).
+	tag := cr.tag;
+	if len(tag) < cap(tag) {
+		nt := len(tag);
+		nn, err1 := io.FullRead(cr.r, tag[nt:cap(tag)]);
+		tag = tag[0:nt+nn];
+		cr.tag = tag;
+		if err1 != nil {
+			return 0, err1;
+		}
+	}
+
+	tagBytes := len(tag);
+	if len(p) > 4*tagBytes {
+		// If p is big, try to read directly into p to avoid a copy.
+		n, err = cr.r.Read(p[tagBytes:len(p)]);
+		if n == 0 {
+			goto out;
+		}
+		// copy old tag into p
+		for i := 0; i < tagBytes; i++ {
+			p[i] = tag[i];
+		}
+		// copy new tag out of p
+		for i := 0; i < tagBytes; i++ {
+			tag[i] = p[n+i];
+		}
+		goto out;
+	}
+
+	// Otherwise, read into p and then slide data
+	n, err = cr.r.Read(p);
+	if n == 0 {
+		goto out;
+	}
+
+	// copy tag+p into p+tmp and then swap tmp, tag
+	tmp := cr.tmp;
+	for i := n + tagBytes - 1; i >= 0; i-- {
+		var c byte;
+		if i < tagBytes {
+			c = tag[i];
+		} else {
+			c = p[i - tagBytes];
+		}
+		if i < n {
+			p[i] = c;
+		} else {
+			tmp[i] = c;
+		}
+	}
+	cr.tmp, cr.tag = tag, tmp;
+
+out:
+	cr.cmac.Write(p[0:n]);
+	return;
+}
+
+type eaxDecrypter struct {
+	ctr io.Reader;
+	cr cmacReader;
+	tag []byte;
+}
+
+// NewEAXDecrypter creates and returns a new EAX decrypter
+// using the given cipher c, initialization vector iv, associated data hdr,
+// and tag length tagBytes.  The encrypter's Read method decrypts and
+// returns data read from r.  At r's EOF, the encrypter checks the final
+// authenticating tag and returns an EAXTagError if the tag is invalid.
+// In that case, the message should be discarded.
+// Note that the data stream returned from Read cannot be
+// assumed to be valid, authenticated data until Read returns
+// 0, nil to signal the end of the data.
+func NewEAXDecrypter(c Cipher, iv []byte, hdr []byte, tagBytes int, r io.Reader) io.Reader {
+	x := new(eaxDecrypter);
+
+	x.cr.r = r;
+	x.cr.tag = make([]byte, 0, tagBytes);
+	x.cr.tmp = make([]byte, 0, tagBytes);
+	var ctrIV []byte;
+	ctrIV, x.tag, x.cr.cmac = setupEAX(c, iv, hdr, tagBytes);
+	x.ctr = NewCTRReader(c, ctrIV, &x.cr);
+	return x;
+}
+
+func (x *eaxDecrypter) checkTag() os.Error {
+	x.ctr = nil;	// crash if Read is called again
+
+	finishEAX(x.tag, x.cr.cmac);
+	if !same(x.tag, x.cr.tag) {
+		e := new(EAXTagError);
+		e.Computed = copy(x.tag);
+		e.Read = copy(x.cr.tag);
+		return e;
+	}
+	return nil;
+}
+
+func (x *eaxDecrypter) Read(p []byte) (n int, err os.Error) {
+	n, err = x.ctr.Read(p);
+	if n == 0 && err == nil {
+		err = x.checkTag();
+	}
+	return n, err;
+}
+
diff --git a/src/lib/crypto/block/eax_aes_test.go b/src/lib/crypto/block/eax_aes_test.go
new file mode 100644
index 00000000000..f0453be8066
--- /dev/null
+++ b/src/lib/crypto/block/eax_aes_test.go
@@ -0,0 +1,239 @@
+// 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 block
+
+import (
+	"crypto/aes";
+	"crypto/block";
+	"fmt";
+	"io";
+	"testing";
+)
+
+// Test vectors from http://www.cs.ucdavis.edu/~rogaway/papers/eax.pdf
+
+type eaxAESTest struct {
+	msg []byte;
+	key []byte;
+	nonce []byte;
+	header []byte;
+	cipher []byte;
+}
+
+var eaxAESTests = []eaxAESTest {
+	eaxAESTest {
+		[]byte {
+		},
+		[]byte {
+			0x23, 0x39, 0x52, 0xDE, 0xE4, 0xD5, 0xED, 0x5F, 0x9B, 0x9C, 0x6D, 0x6F, 0xF8, 0x0F, 0xF4, 0x78,
+		},
+		[]byte {
+			0x62, 0xEC, 0x67, 0xF9, 0xC3, 0xA4, 0xA4, 0x07, 0xFC, 0xB2, 0xA8, 0xC4, 0x90, 0x31, 0xA8, 0xB3,
+		},
+		[]byte {
+			0x6B, 0xFB, 0x91, 0x4F, 0xD0, 0x7E, 0xAE, 0x6B,
+		},
+		[]byte {
+			0xE0, 0x37, 0x83, 0x0E, 0x83, 0x89, 0xF2, 0x7B, 0x02, 0x5A, 0x2D, 0x65, 0x27, 0xE7, 0x9D, 0x01,
+		},
+	},
+	eaxAESTest {
+		[]byte {
+			0xF7, 0xFB,
+		},
+		[]byte {
+			0x91, 0x94, 0x5D, 0x3F, 0x4D, 0xCB, 0xEE, 0x0B, 0xF4, 0x5E, 0xF5, 0x22, 0x55, 0xF0, 0x95, 0xA4,
+		},
+		[]byte {
+			0xBE, 0xCA, 0xF0, 0x43, 0xB0, 0xA2, 0x3D, 0x84, 0x31, 0x94, 0xBA, 0x97, 0x2C, 0x66, 0xDE, 0xBD,
+		},
+		[]byte {
+			0xFA, 0x3B, 0xFD, 0x48, 0x06, 0xEB, 0x53, 0xFA,
+		},
+		[]byte {
+			0x19, 0xDD, 0x5C, 0x4C, 0x93, 0x31, 0x04, 0x9D, 0x0B, 0xDA, 0xB0, 0x27, 0x74, 0x08, 0xF6, 0x79, 0x67, 0xE5,
+		},
+	},
+	eaxAESTest {
+		[]byte {
+			0x1A, 0x47, 0xCB, 0x49, 0x33,
+		},
+		[]byte {
+			0x01, 0xF7, 0x4A, 0xD6, 0x40, 0x77, 0xF2, 0xE7, 0x04, 0xC0, 0xF6, 0x0A, 0xDA, 0x3D, 0xD5, 0x23,
+		},
+		[]byte {
+			0x70, 0xC3, 0xDB, 0x4F, 0x0D, 0x26, 0x36, 0x84, 0x00, 0xA1, 0x0E, 0xD0, 0x5D, 0x2B, 0xFF, 0x5E,
+		},
+		[]byte {
+			0x23, 0x4A, 0x34, 0x63, 0xC1, 0x26, 0x4A, 0xC6,
+		},
+		[]byte {
+			0xD8, 0x51, 0xD5, 0xBA, 0xE0, 0x3A, 0x59, 0xF2, 0x38, 0xA2, 0x3E, 0x39, 0x19, 0x9D, 0xC9, 0x26, 0x66, 0x26, 0xC4, 0x0F, 0x80,
+		},
+	},
+	eaxAESTest {
+		[]byte {
+			0x48, 0x1C, 0x9E, 0x39, 0xB1,
+		},
+		[]byte {
+			0xD0, 0x7C, 0xF6, 0xCB, 0xB7, 0xF3, 0x13, 0xBD, 0xDE, 0x66, 0xB7, 0x27, 0xAF, 0xD3, 0xC5, 0xE8,
+		},
+		[]byte {
+			0x84, 0x08, 0xDF, 0xFF, 0x3C, 0x1A, 0x2B, 0x12, 0x92, 0xDC, 0x19, 0x9E, 0x46, 0xB7, 0xD6, 0x17,
+		},
+		[]byte {
+			0x33, 0xCC, 0xE2, 0xEA, 0xBF, 0xF5, 0xA7, 0x9D,
+		},
+		[]byte {
+			0x63, 0x2A, 0x9D, 0x13, 0x1A, 0xD4, 0xC1, 0x68, 0xA4, 0x22, 0x5D, 0x8E, 0x1F, 0xF7, 0x55, 0x93, 0x99, 0x74, 0xA7, 0xBE, 0xDE,
+		},
+	},
+	eaxAESTest {
+		[]byte {
+			0x40, 0xD0, 0xC0, 0x7D, 0xA5, 0xE4,
+		},
+		[]byte {
+			0x35, 0xB6, 0xD0, 0x58, 0x00, 0x05, 0xBB, 0xC1, 0x2B, 0x05, 0x87, 0x12, 0x45, 0x57, 0xD2, 0xC2,
+		},
+		[]byte {
+			0xFD, 0xB6, 0xB0, 0x66, 0x76, 0xEE, 0xDC, 0x5C, 0x61, 0xD7, 0x42, 0x76, 0xE1, 0xF8, 0xE8, 0x16,
+		},
+		[]byte {
+			0xAE, 0xB9, 0x6E, 0xAE, 0xBE, 0x29, 0x70, 0xE9,
+		},
+		[]byte {
+			0x07, 0x1D, 0xFE, 0x16, 0xC6, 0x75, 0xCB, 0x06, 0x77, 0xE5, 0x36, 0xF7, 0x3A, 0xFE, 0x6A, 0x14, 0xB7, 0x4E, 0xE4, 0x98, 0x44, 0xDD,
+		},
+	},
+	eaxAESTest {
+		[]byte {
+			0x4D, 0xE3, 0xB3, 0x5C, 0x3F, 0xC0, 0x39, 0x24, 0x5B, 0xD1, 0xFB, 0x7D,
+		},
+		[]byte {
+			0xBD, 0x8E, 0x6E, 0x11, 0x47, 0x5E, 0x60, 0xB2, 0x68, 0x78, 0x4C, 0x38, 0xC6, 0x2F, 0xEB, 0x22,
+		},
+		[]byte {
+			0x6E, 0xAC, 0x5C, 0x93, 0x07, 0x2D, 0x8E, 0x85, 0x13, 0xF7, 0x50, 0x93, 0x5E, 0x46, 0xDA, 0x1B,
+		},
+		[]byte {
+			0xD4, 0x48, 0x2D, 0x1C, 0xA7, 0x8D, 0xCE, 0x0F,
+		},
+		[]byte {
+			0x83, 0x5B, 0xB4, 0xF1, 0x5D, 0x74, 0x3E, 0x35, 0x0E, 0x72, 0x84, 0x14, 0xAB, 0xB8, 0x64, 0x4F, 0xD6, 0xCC, 0xB8, 0x69, 0x47, 0xC5, 0xE1, 0x05, 0x90, 0x21, 0x0A, 0x4F,
+		},
+	},
+	eaxAESTest {
+		[]byte {
+			0x8B, 0x0A, 0x79, 0x30, 0x6C, 0x9C, 0xE7, 0xED, 0x99, 0xDA, 0xE4, 0xF8, 0x7F, 0x8D, 0xD6, 0x16, 0x36,
+		},
+		[]byte {
+			0x7C, 0x77, 0xD6, 0xE8, 0x13, 0xBE, 0xD5, 0xAC, 0x98, 0xBA, 0xA4, 0x17, 0x47, 0x7A, 0x2E, 0x7D,
+		},
+		[]byte {
+			0x1A, 0x8C, 0x98, 0xDC, 0xD7, 0x3D, 0x38, 0x39, 0x3B, 0x2B, 0xF1, 0x56, 0x9D, 0xEE, 0xFC, 0x19,
+		},
+		[]byte {
+			0x65, 0xD2, 0x01, 0x79, 0x90, 0xD6, 0x25, 0x28,
+		},
+		[]byte {
+			0x02, 0x08, 0x3E, 0x39, 0x79, 0xDA, 0x01, 0x48, 0x12, 0xF5, 0x9F, 0x11, 0xD5, 0x26, 0x30, 0xDA, 0x30, 0x13, 0x73, 0x27, 0xD1, 0x06, 0x49, 0xB0, 0xAA, 0x6E, 0x1C, 0x18, 0x1D, 0xB6, 0x17, 0xD7, 0xF2,
+		},
+	},
+	eaxAESTest {
+		[]byte {
+			0x1B, 0xDA, 0x12, 0x2B, 0xCE, 0x8A, 0x8D, 0xBA, 0xF1, 0x87, 0x7D, 0x96, 0x2B, 0x85, 0x92, 0xDD, 0x2D, 0x56,
+		},
+		[]byte {
+			0x5F, 0xFF, 0x20, 0xCA, 0xFA, 0xB1, 0x19, 0xCA, 0x2F, 0xC7, 0x35, 0x49, 0xE2, 0x0F, 0x5B, 0x0D,
+		},
+		[]byte {
+			0xDD, 0xE5, 0x9B, 0x97, 0xD7, 0x22, 0x15, 0x6D, 0x4D, 0x9A, 0xFF, 0x2B, 0xC7, 0x55, 0x98, 0x26,
+		},
+		[]byte {
+			0x54, 0xB9, 0xF0, 0x4E, 0x6A, 0x09, 0x18, 0x9A,
+		},
+		[]byte {
+			0x2E, 0xC4, 0x7B, 0x2C, 0x49, 0x54, 0xA4, 0x89, 0xAF, 0xC7, 0xBA, 0x48, 0x97, 0xED, 0xCD, 0xAE, 0x8C, 0xC3, 0x3B, 0x60, 0x45, 0x05, 0x99, 0xBD, 0x02, 0xC9, 0x63, 0x82, 0x90, 0x2A, 0xEF, 0x7F, 0x83, 0x2A,
+		},
+	},
+	eaxAESTest {
+		[]byte {
+			0x6C, 0xF3, 0x67, 0x20, 0x87, 0x2B, 0x85, 0x13, 0xF6, 0xEA, 0xB1, 0xA8, 0xA4, 0x44, 0x38, 0xD5, 0xEF, 0x11,
+		},
+		[]byte {
+			0xA4, 0xA4, 0x78, 0x2B, 0xCF, 0xFD, 0x3E, 0xC5, 0xE7, 0xEF, 0x6D, 0x8C, 0x34, 0xA5, 0x61, 0x23,
+		},
+		[]byte {
+			0xB7, 0x81, 0xFC, 0xF2, 0xF7, 0x5F, 0xA5, 0xA8, 0xDE, 0x97, 0xA9, 0xCA, 0x48, 0xE5, 0x22, 0xEC,
+		},
+		[]byte {
+			0x89, 0x9A, 0x17, 0x58, 0x97, 0x56, 0x1D, 0x7E,
+		},
+		[]byte {
+			0x0D, 0xE1, 0x8F, 0xD0, 0xFD, 0xD9, 0x1E, 0x7A, 0xF1, 0x9F, 0x1D, 0x8E, 0xE8, 0x73, 0x39, 0x38, 0xB1, 0xE8, 0xE7, 0xF6, 0xD2, 0x23, 0x16, 0x18, 0x10, 0x2F, 0xDB, 0x7F, 0xE5, 0x5F, 0xF1, 0x99, 0x17, 0x00,
+		},
+	},
+	eaxAESTest {
+		[]byte {
+			0xCA, 0x40, 0xD7, 0x44, 0x6E, 0x54, 0x5F, 0xFA, 0xED, 0x3B, 0xD1, 0x2A, 0x74, 0x0A, 0x65, 0x9F, 0xFB, 0xBB, 0x3C, 0xEA, 0xB7,
+		},
+		[]byte {
+			0x83, 0x95, 0xFC, 0xF1, 0xE9, 0x5B, 0xEB, 0xD6, 0x97, 0xBD, 0x01, 0x0B, 0xC7, 0x66, 0xAA, 0xC3,
+		},
+		[]byte {
+			0x22, 0xE7, 0xAD, 0xD9, 0x3C, 0xFC, 0x63, 0x93, 0xC5, 0x7E, 0xC0, 0xB3, 0xC1, 0x7D, 0x6B, 0x44,
+		},
+		[]byte {
+			0x12, 0x67, 0x35, 0xFC, 0xC3, 0x20, 0xD2, 0x5A,
+		},
+		[]byte {
+			0xCB, 0x89, 0x20, 0xF8, 0x7A, 0x6C, 0x75, 0xCF, 0xF3, 0x96, 0x27, 0xB5, 0x6E, 0x3E, 0xD1, 0x97, 0xC5, 0x52, 0xD2, 0x95, 0xA7, 0xCF, 0xC4, 0x6A, 0xFC, 0x25, 0x3B, 0x46, 0x52, 0xB1, 0xAF, 0x37, 0x95, 0xB1, 0x24, 0xAB, 0x6E,
+		},
+	},
+}
+
+func TestEAXEncrypt_AES(t *testing.T) {
+	b := new(io.ByteBuffer);
+	for i, tt := range eaxAESTests {
+		test := fmt.Sprintf("test %d", i);
+		c, err := aes.NewCipher(tt.key);
+		if err != nil {
+			t.Fatalf("%s: NewCipher(%d bytes) = %s", test, len(tt.key), err);
+		}
+		b.Reset();
+		enc := NewEAXEncrypter(c, tt.nonce, tt.header, 16, b);
+		n, err := io.Copy(io.NewByteReader(tt.msg), enc);
+		if n != int64(len(tt.msg)) || err != nil {
+			t.Fatalf("%s: io.Copy into encrypter: %d, %s", test, n, err);
+		}
+		err = enc.Close();
+		if err != nil {
+			t.Fatalf("%s: enc.Close: %s", test, err);
+		}
+		if d := b.Data(); !same(d, tt.cipher) {
+			t.Fatalf("%s: got %x want %x", test, d, tt.cipher);
+		}
+	}
+}
+
+func TestEAXDecrypt_AES(t *testing.T) {
+	b := new(io.ByteBuffer);
+	for i, tt := range eaxAESTests {
+		test := fmt.Sprintf("test %d", i);
+		c, err := aes.NewCipher(tt.key);
+		if err != nil {
+			t.Fatalf("%s: NewCipher(%d bytes) = %s", test, len(tt.key), err);
+		}
+		b.Reset();
+		dec := NewEAXDecrypter(c, tt.nonce, tt.header, 16, io.NewByteReader(tt.cipher));
+		n, err := io.Copy(dec, b);
+		if n != int64(len(tt.msg)) || err != nil {
+			t.Fatalf("%s: io.Copy into decrypter: %d, %s", test, n, err);
+		}
+		if d := b.Data(); !same(d, tt.msg) {
+			t.Fatalf("%s: got %x want %x", test, d, tt.msg);
+		}
+	}
+}
diff --git a/src/lib/crypto/block/ofb.go b/src/lib/crypto/block/ofb.go
index 10f9a77371e..084274a084f 100644
--- a/src/lib/crypto/block/ofb.go
+++ b/src/lib/crypto/block/ofb.go
@@ -45,7 +45,7 @@ func (x *ofbStream) Next() []byte {
 // an OFB reader applied to an encrypted stream produces a decrypted
 // stream and vice versa.
 func NewOFBReader(c Cipher, iv []byte, r io.Reader) io.Reader {
-	return NewXorReader(newOFBStream(c, iv), r);
+	return newXorReader(newOFBStream(c, iv), r);
 }
 
 // NewOFBWriter returns a writer that encrypts (or decrypts) data using c
@@ -56,6 +56,6 @@ func NewOFBReader(c Cipher, iv []byte, r io.Reader) io.Reader {
 // an OFB writer applied to an decrypted stream produces an encrypted
 // stream and vice versa.
 func NewOFBWriter(c Cipher, iv []byte, w io.Writer) io.Writer {
-	return NewXorWriter(newOFBStream(c, iv), w);
+	return newXorWriter(newOFBStream(c, iv), w);
 }
 
diff --git a/src/lib/crypto/block/xor.go b/src/lib/crypto/block/xor.go
index 35c18138442..63229dbb403 100644
--- a/src/lib/crypto/block/xor.go
+++ b/src/lib/crypto/block/xor.go
@@ -12,17 +12,21 @@ import (
 	"os";
 )
 
-type DataStream interface {
+// A dataStream is an interface to an unending stream of data,
+// used by XorReader and XorWriter to model a pseudo-random generator.
+// Calls to Next() return sequential blocks of data from the stream.
+// Each call must return at least one byte: there is no EOF.
+type dataStream interface {
 	Next() []byte
 }
 
 type xorReader struct {
 	r io.Reader;
-	rand DataStream;	// pseudo-random
+	rand dataStream;	// pseudo-random
 	buf []byte;		// data available from last call to rand
 }
 
-func NewXorReader(rand DataStream, r io.Reader) io.Reader {
+func newXorReader(rand dataStream, r io.Reader) io.Reader {
 	x := new(xorReader);
 	x.r = r;
 	x.rand = rand;
@@ -49,13 +53,13 @@ func (x *xorReader) Read(p []byte) (n int, err os.Error) {
 
 type xorWriter struct {
 	w io.Writer;
-	rand DataStream;	// pseudo-random
+	rand dataStream;	// pseudo-random
 	buf []byte;	// last buffer returned by rand
 	extra []byte;	// extra random data (use before buf)
 	work []byte;	// work space
 }
 
-func NewXorWriter(rand DataStream, w io.Writer) io.Writer {
+func newXorWriter(rand dataStream, w io.Writer) io.Writer {
 	x := new(xorWriter);
 	x.w = w;
 	x.rand = rand;
diff --git a/src/lib/crypto/block/xor_test.go b/src/lib/crypto/block/xor_test.go
index a2166f884cb..6e6d1a3ce97 100644
--- a/src/lib/crypto/block/xor_test.go
+++ b/src/lib/crypto/block/xor_test.go
@@ -55,7 +55,7 @@ func testXorWriter(t *testing.T, maxio int) {
 			b.Reset();
 			r := io.NewByteReader(&plain);
 			s := newIncStream(block);
-			w := NewXorWriter(s, b);
+			w := newXorWriter(s, b);
 
 			// copy plain into w in increasingly large chunks: 1, 1, 2, 4, 8, ...
 			// if frag != 0, move the 1 to the end to cause fragmentation.
@@ -123,7 +123,7 @@ func testXorReader(t *testing.T, maxio int) {
 				test := fmt.Sprintf("block=%d mode=%d frag=%d maxio=%d", block, mode, frag, maxio);
 				s := newIncStream(block);
 				b.Reset();
-				r := NewXorReader(s, readers[mode](io.NewByteReader(crypt[0:maxio])));
+				r := newXorReader(s, readers[mode](io.NewByteReader(crypt[0:maxio])));
 
 				// read from crypt in increasingly large chunks: 1, 1, 2, 4, 8, ...
 				// if frag == 1, move the 1 to the end to cause fragmentation.