diff --git a/src/pkg/Makefile b/src/pkg/Makefile
index c7e65c029e..85c5031e51 100644
--- a/src/pkg/Makefile
+++ b/src/pkg/Makefile
@@ -33,6 +33,7 @@ DIRS=\
 	crypto\
 	crypto/aes\
 	crypto/blowfish\
+	crypto/bcrypt\
 	crypto/cast5\
 	crypto/cipher\
 	crypto/des\
diff --git a/src/pkg/crypto/bcrypt/Makefile b/src/pkg/crypto/bcrypt/Makefile
new file mode 100644
index 0000000000..3c83d9c8ae
--- /dev/null
+++ b/src/pkg/crypto/bcrypt/Makefile
@@ -0,0 +1,12 @@
+# Copyright 2011 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 ../../../Make.inc
+
+TARG=crypto/bcrypt
+GOFILES=\
+	base64.go \
+	bcrypt.go
+
+include ../../../Make.pkg
diff --git a/src/pkg/crypto/bcrypt/base64.go b/src/pkg/crypto/bcrypt/base64.go
new file mode 100644
index 0000000000..ed6cea70c5
--- /dev/null
+++ b/src/pkg/crypto/bcrypt/base64.go
@@ -0,0 +1,38 @@
+// Copyright 2011 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 bcrypt
+
+import (
+	"encoding/base64"
+	"os"
+)
+
+const alphabet = "./ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
+
+var bcEncoding = base64.NewEncoding(alphabet)
+
+func base64Encode(src []byte) []byte {
+	n := bcEncoding.EncodedLen(len(src))
+	dst := make([]byte, n)
+	bcEncoding.Encode(dst, src)
+	for dst[n-1] == '=' {
+		n--
+	}
+	return dst[:n]
+}
+
+func base64Decode(src []byte) ([]byte, os.Error) {
+	numOfEquals := 4 - (len(src) % 4)
+	for i := 0; i < numOfEquals; i++ {
+		src = append(src, '=')
+	}
+
+	dst := make([]byte, bcEncoding.DecodedLen(len(src)))
+	n, err := bcEncoding.Decode(dst, src)
+	if err != nil {
+		return nil, err
+	}
+	return dst[:n], nil
+}
diff --git a/src/pkg/crypto/bcrypt/bcrypt.go b/src/pkg/crypto/bcrypt/bcrypt.go
new file mode 100644
index 0000000000..1e8ccfac19
--- /dev/null
+++ b/src/pkg/crypto/bcrypt/bcrypt.go
@@ -0,0 +1,282 @@
+// Copyright 2011 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 bcrypt implements Provos and Mazières's bcrypt adapative hashing
+// algorithm. See http://www.usenix.org/event/usenix99/provos/provos.pdf
+package bcrypt
+
+// The code is a port of Provos and Mazières's C implementation. 
+import (
+	"crypto/blowfish"
+	"crypto/rand"
+	"crypto/subtle"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+)
+
+const (
+	MinCost     int = 4  // the minimum allowable cost as passed in to GenerateFromPassword
+	MaxCost     int = 31 // the maximum allowable cost as passed in to GenerateFromPassword
+	DefaultCost int = 10 // the cost that will actually be set if a cost below MinCost is passed into GenerateFromPassword
+)
+
+// The error returned from CompareHashAndPassword when a password and hash do
+// not match.
+var MismatchedHashAndPasswordError = os.NewError("crypto/bcrypt: hashedPassword is not the hash of the given password")
+
+// The error returned from CompareHashAndPassword when a hash is too short to
+// be a bcrypt hash.
+var HashTooShortError = os.NewError("crypto/bcrypt: hashedSecret too short to be a bcrypted password")
+
+// The error returned from CompareHashAndPassword when a hash was created with
+// a bcrypt algorithm newer than this implementation.
+type HashVersionTooNewError byte
+
+func (hv HashVersionTooNewError) String() string {
+	return fmt.Sprintf("crypto/bcrypt: bcrypt algorithm version '%c' requested is newer than current version '%c'", byte(hv), majorVersion)
+}
+
+// The error returned from CompareHashAndPassword when a hash starts with something other than '$'
+type InvalidHashPrefixError byte
+
+func (ih InvalidHashPrefixError) String() string {
+	return fmt.Sprintf("crypto/bcrypt: bcrypt hashes must start with '$', but hashedSecret started with '%c'", byte(ih))
+}
+
+type InvalidCostError int
+
+func (ic InvalidCostError) String() string {
+	return fmt.Sprintf("crypto/bcrypt: cost %d is outside allowed range (%d,%d)", int(ic), int(MinCost), int(MaxCost))
+}
+
+const (
+	majorVersion       = '2'
+	minorVersion       = 'a'
+	maxSaltSize        = 16
+	maxCryptedHashSize = 23
+	encodedSaltSize    = 22
+	encodedHashSize    = 31
+	minHashSize        = 59
+)
+
+// magicCipherData is an IV for the 64 Blowfish encryption calls in
+// bcrypt(). It's the string "OrpheanBeholderScryDoubt" in big-endian bytes.
+var magicCipherData = []byte{
+	0x4f, 0x72, 0x70, 0x68,
+	0x65, 0x61, 0x6e, 0x42,
+	0x65, 0x68, 0x6f, 0x6c,
+	0x64, 0x65, 0x72, 0x53,
+	0x63, 0x72, 0x79, 0x44,
+	0x6f, 0x75, 0x62, 0x74,
+}
+
+type hashed struct {
+	hash  []byte
+	salt  []byte
+	cost  uint32 // allowed range is MinCost to MaxCost
+	major byte
+	minor byte
+}
+
+// GenerateFromPassword returns the bcrypt hash of the password at the given
+// cost. If the cost given is less than MinCost, the cost will be set to
+// MinCost, instead. Use CompareHashAndPassword, as defined in this package,
+// to compare the returned hashed password with its cleartext version.
+func GenerateFromPassword(password []byte, cost int) ([]byte, os.Error) {
+	p, err := newFromPassword(password, cost)
+	if err != nil {
+		return nil, err
+	}
+	return p.Hash(), nil
+}
+
+// CompareHashAndPassword compares a bcrypt hashed password with its possible
+// plaintext equivalent. Note: Using bytes.Equal for this job is
+// insecure. Returns nil on success, or an error on failure.
+func CompareHashAndPassword(hashedPassword, password []byte) os.Error {
+	p, err := newFromHash(hashedPassword)
+	if err != nil {
+		return err
+	}
+
+	otherHash, err := bcrypt(password, p.cost, p.salt)
+	if err != nil {
+		return err
+	}
+
+	otherP := &hashed{otherHash, p.salt, p.cost, p.major, p.minor}
+	if subtle.ConstantTimeCompare(p.Hash(), otherP.Hash()) == 1 {
+		return nil
+	}
+
+	return MismatchedHashAndPasswordError
+}
+
+func newFromPassword(password []byte, cost int) (*hashed, os.Error) {
+	if cost < MinCost {
+		cost = DefaultCost
+	}
+	p := new(hashed)
+	p.major = majorVersion
+	p.minor = minorVersion
+
+	err := checkCost(cost)
+	if err != nil {
+		return nil, err
+	}
+	p.cost = uint32(cost)
+
+	unencodedSalt := make([]byte, maxSaltSize)
+	_, err = io.ReadFull(rand.Reader, unencodedSalt)
+	if err != nil {
+		return nil, err
+	}
+
+	p.salt = base64Encode(unencodedSalt)
+	hash, err := bcrypt(password, p.cost, p.salt)
+	if err != nil {
+		return nil, err
+	}
+	p.hash = hash
+	return p, err
+}
+
+func newFromHash(hashedSecret []byte) (*hashed, os.Error) {
+	if len(hashedSecret) < minHashSize {
+		return nil, HashTooShortError
+	}
+	p := new(hashed)
+	n, err := p.decodeVersion(hashedSecret)
+	if err != nil {
+		return nil, err
+	}
+	hashedSecret = hashedSecret[n:]
+	n, err = p.decodeCost(hashedSecret)
+	if err != nil {
+		return nil, err
+	}
+	hashedSecret = hashedSecret[n:]
+
+	// The "+2" is here because we'll have to append at most 2 '=' to the salt
+	// when base64 decoding it in expensiveBlowfishSetup().
+	p.salt = make([]byte, encodedSaltSize, encodedSaltSize+2)
+	copy(p.salt, hashedSecret[:encodedSaltSize])
+
+	hashedSecret = hashedSecret[encodedSaltSize:]
+	p.hash = make([]byte, len(hashedSecret))
+	copy(p.hash, hashedSecret)
+
+	return p, nil
+}
+
+func bcrypt(password []byte, cost uint32, salt []byte) ([]byte, os.Error) {
+	cipherData := make([]byte, len(magicCipherData))
+	copy(cipherData, magicCipherData)
+
+	c, err := expensiveBlowfishSetup(password, cost, salt)
+	if err != nil {
+		return nil, err
+	}
+
+	for i := 0; i < 24; i += 8 {
+		for j := 0; j < 64; j++ {
+			c.Encrypt(cipherData[i:i+8], cipherData[i:i+8])
+		}
+	}
+
+	// Bug compatibility with C bcrypt implementations. We only encode 23 of
+	// the 24 bytes encrypted.
+	hsh := base64Encode(cipherData[:maxCryptedHashSize])
+	return hsh, nil
+}
+
+func expensiveBlowfishSetup(key []byte, cost uint32, salt []byte) (*blowfish.Cipher, os.Error) {
+
+	csalt, err := base64Decode(salt)
+	if err != nil {
+		return nil, err
+	}
+
+	// Bug compatibility with C bcrypt implementations. They use the trailing
+	// NULL in the key string during expansion.
+	ckey := append(key, 0)
+
+	c, err := blowfish.NewSaltedCipher(ckey, csalt)
+	if err != nil {
+		return nil, err
+	}
+
+	rounds := 1 << cost
+	for i := 0; i < rounds; i++ {
+		blowfish.ExpandKey(ckey, c)
+		blowfish.ExpandKey(csalt, c)
+	}
+
+	return c, nil
+}
+
+func (p *hashed) Hash() []byte {
+	arr := make([]byte, 60)
+	arr[0] = '$'
+	arr[1] = p.major
+	n := 2
+	if p.minor != 0 {
+		arr[2] = p.minor
+		n = 3
+	}
+	arr[n] = '$'
+	n += 1
+	copy(arr[n:], []byte(fmt.Sprintf("%02d", p.cost)))
+	n += 2
+	arr[n] = '$'
+	n += 1
+	copy(arr[n:], p.salt)
+	n += encodedSaltSize
+	copy(arr[n:], p.hash)
+	n += encodedHashSize
+	return arr[:n]
+}
+
+func (p *hashed) decodeVersion(sbytes []byte) (int, os.Error) {
+	if sbytes[0] != '$' {
+		return -1, InvalidHashPrefixError(sbytes[0])
+	}
+	if sbytes[1] > majorVersion {
+		return -1, HashVersionTooNewError(sbytes[1])
+	}
+	p.major = sbytes[1]
+	n := 3
+	if sbytes[2] != '$' {
+		p.minor = sbytes[2]
+		n++
+	}
+	return n, nil
+}
+
+// sbytes should begin where decodeVersion left off.
+func (p *hashed) decodeCost(sbytes []byte) (int, os.Error) {
+	cost, err := strconv.Atoi(string(sbytes[0:2]))
+	if err != nil {
+		return -1, err
+	}
+	err = checkCost(cost)
+	if err != nil {
+		return -1, err
+	}
+	p.cost = uint32(cost)
+	return 3, nil
+}
+
+func (p *hashed) String() string {
+	return fmt.Sprintf("&{hash: %#v, salt: %#v, cost: %d, major: %c, minor: %c}", string(p.hash), p.salt, p.cost, p.major, p.minor)
+}
+
+func checkCost(cost int) os.Error {
+	if cost < MinCost || cost > MaxCost {
+		return InvalidCostError(cost)
+	}
+	return nil
+}
diff --git a/src/pkg/crypto/bcrypt/bcrypt_test.go b/src/pkg/crypto/bcrypt/bcrypt_test.go
new file mode 100644
index 0000000000..89eca0a448
--- /dev/null
+++ b/src/pkg/crypto/bcrypt/bcrypt_test.go
@@ -0,0 +1,195 @@
+// Copyright 2011 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 bcrypt
+
+import (
+	"bytes"
+	"os"
+	"testing"
+)
+
+func TestBcryptingIsEasy(t *testing.T) {
+	pass := []byte("mypassword")
+	hp, err := GenerateFromPassword(pass, 0)
+	if err != nil {
+		t.Fatalf("GenerateFromPassword error: %s", err)
+	}
+
+	if CompareHashAndPassword(hp, pass) != nil {
+		t.Errorf("%v should hash %s correctly", hp, pass)
+	}
+
+	notPass := "notthepass"
+	err = CompareHashAndPassword(hp, []byte(notPass))
+	if err != MismatchedHashAndPasswordError {
+		t.Errorf("%v and %s should be mismatched", hp, notPass)
+	}
+}
+
+func TestBcryptingIsCorrect(t *testing.T) {
+	pass := []byte("allmine")
+	salt := []byte("XajjQvNhvvRt5GSeFk1xFe")
+	expectedHash := []byte("$2a$10$XajjQvNhvvRt5GSeFk1xFeyqRrsxkhBkUiQeg0dt.wU1qD4aFDcga")
+
+	hash, err := bcrypt(pass, 10, salt)
+	if err != nil {
+		t.Fatalf("bcrypt blew up: %v", err)
+	}
+	if !bytes.HasSuffix(expectedHash, hash) {
+		t.Errorf("%v should be the suffix of %v", hash, expectedHash)
+	}
+
+	h, err := newFromHash(expectedHash)
+	if err != nil {
+		t.Errorf("Unable to parse %s: %v", string(expectedHash), err)
+	}
+
+	// This is not the safe way to compare these hashes. We do this only for
+	// testing clarity. Use bcrypt.CompareHashAndPassword()
+	if err == nil && !bytes.Equal(expectedHash, h.Hash()) {
+		t.Errorf("Parsed hash %v should equal %v", h.Hash(), expectedHash)
+	}
+}
+
+func TestTooLongPasswordsWork(t *testing.T) {
+	salt := []byte("XajjQvNhvvRt5GSeFk1xFe")
+	// One byte over the usual 56 byte limit that blowfish has
+	tooLongPass := []byte("012345678901234567890123456789012345678901234567890123456")
+	tooLongExpected := []byte("$2a$10$XajjQvNhvvRt5GSeFk1xFe5l47dONXg781AmZtd869sO8zfsHuw7C")
+	hash, err := bcrypt(tooLongPass, 10, salt)
+	if err != nil {
+		t.Fatalf("bcrypt blew up on long password: %v", err)
+	}
+	if !bytes.HasSuffix(tooLongExpected, hash) {
+		t.Errorf("%v should be the suffix of %v", hash, tooLongExpected)
+	}
+}
+
+type InvalidHashTest struct {
+	err  os.Error
+	hash []byte
+}
+
+var invalidTests = []InvalidHashTest{
+	{HashTooShortError, []byte("$2a$10$fooo")},
+	{HashTooShortError, []byte("$2a")},
+	{HashVersionTooNewError('3'), []byte("$3a$10$sssssssssssssssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh")},
+	{InvalidHashPrefixError('%'), []byte("%2a$10$sssssssssssssssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh")},
+	{InvalidCostError(32), []byte("$2a$32$sssssssssssssssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh")},
+}
+
+func TestInvalidHashErrors(t *testing.T) {
+	check := func(name string, expected, err os.Error) {
+		if err == nil {
+			t.Errorf("%s: Should have returned an error", name)
+		}
+		if err != nil && err != expected {
+			t.Errorf("%s gave err %v but should have given %v", name, err.String(), expected.String())
+		}
+	}
+	for _, iht := range invalidTests {
+		_, err := newFromHash(iht.hash)
+		check("newFromHash", iht.err, err)
+		err = CompareHashAndPassword(iht.hash, []byte("anything"))
+		check("CompareHashAndPassword", iht.err, err)
+	}
+}
+
+func TestUnpaddedBase64Encoding(t *testing.T) {
+	original := []byte{101, 201, 101, 75, 19, 227, 199, 20, 239, 236, 133, 32, 30, 109, 243, 30}
+	encodedOriginal := []byte("XajjQvNhvvRt5GSeFk1xFe")
+
+	encoded := base64Encode(original)
+
+	if !bytes.Equal(encodedOriginal, encoded) {
+		t.Errorf("Encoded %v should have equaled %v", encoded, encodedOriginal)
+	}
+
+	decoded, err := base64Decode(encodedOriginal)
+	if err != nil {
+		t.Fatalf("base64Decode blew up: %s", err)
+	}
+
+	if !bytes.Equal(decoded, original) {
+		t.Errorf("Decoded %v should have equaled %v", decoded, original)
+	}
+}
+
+func TestCost(t *testing.T) {
+	if testing.Short() {
+		return
+	}
+
+	pass := []byte("mypassword")
+
+	for c := 0; c < MinCost; c++ {
+		p, _ := newFromPassword(pass, c)
+		if p.cost != uint32(DefaultCost) {
+			t.Errorf("newFromPassword should default costs below %d to %d, but was %d", MinCost, DefaultCost, p.cost)
+		}
+	}
+
+	p, _ := newFromPassword(pass, 14)
+	if p.cost != 14 {
+		t.Errorf("newFromPassword should default cost to 14, but was %d", p.cost)
+	}
+
+	hp, _ := newFromHash(p.Hash())
+	if p.cost != hp.cost {
+		t.Errorf("newFromHash should maintain the cost at %d, but was %d", p.cost, hp.cost)
+	}
+
+	_, err := newFromPassword(pass, 32)
+	if err == nil {
+		t.Fatalf("newFromPassword: should return a cost error")
+	}
+	if err != InvalidCostError(32) {
+		t.Errorf("newFromPassword: should return cost error, got %#v", err)
+	}
+}
+
+func TestCostReturnsWithLeadingZeroes(t *testing.T) {
+	hp, _ := newFromPassword([]byte("abcdefgh"), 7)
+	cost := hp.Hash()[4:7]
+	expected := []byte("07$")
+
+	if !bytes.Equal(expected, cost) {
+		t.Errorf("single digit costs in hash should have leading zeros: was %v instead of %v", cost, expected)
+	}
+}
+
+func TestMinorNotRequired(t *testing.T) {
+	noMinorHash := []byte("$2$10$XajjQvNhvvRt5GSeFk1xFeyqRrsxkhBkUiQeg0dt.wU1qD4aFDcga")
+	h, err := newFromHash(noMinorHash)
+	if err != nil {
+		t.Fatalf("No minor hash blew up: %s", err)
+	}
+	if h.minor != 0 {
+		t.Errorf("Should leave minor version at 0, but was %d", h.minor)
+	}
+
+	if !bytes.Equal(noMinorHash, h.Hash()) {
+		t.Errorf("Should generate hash %v, but created %v", noMinorHash, h.Hash())
+	}
+}
+
+func BenchmarkEqual(b *testing.B) {
+	b.StopTimer()
+	passwd := []byte("somepasswordyoulike")
+	hash, _ := GenerateFromPassword(passwd, 10)
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		CompareHashAndPassword(hash, passwd)
+	}
+}
+
+func BenchmarkGeneration(b *testing.B) {
+	b.StopTimer()
+	passwd := []byte("mylongpassword1234")
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		GenerateFromPassword(passwd, 10)
+	}
+}