Merge pull request #773 from Roasbeef/aezeed

aezeed: add new package implementing the aezeed cipher seed scheme

aezeed/bench_test.go

@@ -0,0 +1,69 @@
+package aezeed
+
+import (
+	"testing"
+	"time"
+)
+
+var (
+	mnemonic Mnemonic
+
+	seed *CipherSeed
+)
+
+// BenchmarkFrommnemonic benchmarks the process of converting a cipher seed
+// (given the salt), to an enciphered mnemonic.
+func BenchmarkTomnemonic(b *testing.B) {
+	scryptN = 32768
+	scryptR = 8
+	scryptP = 1
+
+	pass := []byte("1234567890abcedfgh")
+	cipherSeed, err := New(0, nil, time.Now())
+	if err != nil {
+		b.Fatalf("unable to create seed: %v", err)
+	}
+
+	var r Mnemonic
+	for i := 0; i < b.N; i++ {
+		r, err = cipherSeed.ToMnemonic(pass)
+		if err != nil {
+			b.Fatalf("unable to encipher: %v", err)
+		}
+	}
+
+	b.ReportAllocs()
+
+	mnemonic = r
+}
+
+// BenchmarkToCipherSeed benchmarks the process of deciphering an existing
+// enciphered mnemonic.
+func BenchmarkToCipherSeed(b *testing.B) {
+	scryptN = 32768
+	scryptR = 8
+	scryptP = 1
+
+	pass := []byte("1234567890abcedfgh")
+	cipherSeed, err := New(0, nil, time.Now())
+	if err != nil {
+		b.Fatalf("unable to create seed: %v", err)
+	}
+
+	mnemonic, err := cipherSeed.ToMnemonic(pass)
+	if err != nil {
+		b.Fatalf("unable to create mnemonic: %v", err)
+	}
+
+	var s *CipherSeed
+	for i := 0; i < b.N; i++ {
+		s, err = mnemonic.ToCipherSeed(pass)
+		if err != nil {
+			b.Fatalf("unable to decipher: %v", err)
+		}
+	}
+
+	b.ReportAllocs()
+
+	seed = s
+}

aezeed/cipherseed.go

@@ -0,0 +1,547 @@
+package aezeed
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/binary"
+	"hash/crc32"
+	"io"
+	"strings"
+	"time"
+
+	"github.com/Yawning/aez"
+	"github.com/kkdai/bstream"
+
+	"golang.org/x/crypto/scrypt"
+)
+
+const (
+	// CipherSeedVersion is the current version of the aezeed scheme as
+	// defined in this package. This version indicates the following
+	// parameters for the deciphered cipher seed: a 1 byte version, 2 bytes
+	// for the Bitcoin Days Genesis timestamp, and 16 bytes for entropy. It
+	// also governs how the cipher seed should be enciphered. In this
+	// version we take the deciphered seed, create a 5 byte salt, use that
+	// with an optional passphrase to generate a 32-byte key (via scrypt),
+	// then encipher with aez (using the salt and version as AD). The final
+	// enciphered seed is: version || ciphertext || salt.
+	CipherSeedVersion uint8 = 0
+
+	// DecipheredCipherSeedSize is the size of the plaintext seed resulting
+	// from deciphering the cipher seed. The size consists of the
+	// following:
+	//
+	//  * 1 byte version || 2 bytes timestamp || 16 bytes of entropy.
+	//
+	// The version is used by wallets to know how to re-derive relevant
+	// addresses, the 2 byte timestamp a BDG (Bitcoin Days Genesis) offset,
+	// and finally, the 16 bytes to be used to generate the HD wallet seed.
+	DecipheredCipherSeedSize = 19
+
+	// EncipheredCipherSeedSize is the size of the fully encoded+enciphered
+	// cipher seed. We first obtain the enciphered plaintext seed by
+	// carrying out the enciphering as governed in the current version. We
+	// then take that enciphered seed (now 19+4=23 bytes due to ciphertext
+	// expansion, essentially a checksum) and prepend a version, then
+	// append the salt, and then take a checksum of everything. The
+	// checksum allows us to verify that the user input the correct set of
+	// words, then we can verify the passphrase due to the internal MAC
+	// equiv.  The final breakdown is:
+	//
+	//  * 1 byte version || 23 byte enciphered seed || 5 byte salt || 4 byte checksum
+	//
+	// With CipherSeedVersion we encipher as follows: we use
+	// scrypt(n=32768, r=8, p=1) to derive a 32-byte key from an optional
+	// user passphrase. We then encipher the plaintext seed using a value
+	// of tau (with aez) of 8-bytes (so essentially a 32-bit MAC).  When
+	// enciphering, we include the version and scrypt salt as the AD.  This
+	// gives us a total of 33 bytes. These 33 bytes fit cleanly into 24
+	// mnemonic words.
+	EncipheredCipherSeedSize = 33
+
+	// CipherTextExpansion is the number of bytes that will be added as
+	// redundancy for the enciphering scheme implemented by aez. This can
+	// be seen as the size of the equivalent MAC.
+	CipherTextExpansion = 4
+
+	// EntropySize is the number of bytes of entropy we'll use the generate
+	// the seed.
+	EntropySize = 16
+
+	// NummnemonicWords is the number of words that an encoded cipher seed
+	// will result in.
+	NummnemonicWords = 24
+
+	// saltSize is the size of the salt we'll generate to use with scrypt
+	// to generate a key for use within aez from the user's passphrase. The
+	// role of the salt is to make the creation of rainbow tables
+	// infeasible.
+	saltSize = 5
+
+	// adSize is the size of the encoded associated data that will be
+	// passed into aez when enciphering and deciphering the seed. The AD
+	// itself (associated data) is just the CipherSeedVersion and salt.
+	adSize = 6
+
+	// checkSumSize is the size of the checksum applied to the final
+	// encoded ciphertext.
+	checkSumSize = 4
+
+	// keyLen is the size of the key that we'll use for encryption with
+	// aez.
+	keyLen = 32
+
+	// bitsPerWord is the number of bits each word in the wordlist encodes.
+	// We encode our mnemonic using 24 words, so 264 bits (33 bytes).
+	bitsPerWord = 11
+
+	// saltOffset is the index within an enciphered cipherseed that marks
+	// the start of the salt.
+	saltOffset = EncipheredCipherSeedSize - checkSumSize - saltSize
+
+	// checkSumSize is the index within an enciphered cipher seed that
+	// marks the start of the checksum.
+	checkSumOffset = EncipheredCipherSeedSize - checkSumSize
+
+	// encipheredSeedSize is the size of the cipherseed before applying the
+	// external version, salt, and checksum for the final encoding.
+	encipheredSeedSize = DecipheredCipherSeedSize + CipherTextExpansion
+)
+
+var (
+	// Below at the default scrypt parameters that are tied to
+	// CipherSeedVersion zero.
+	scryptN = 32768
+	scryptR = 8
+	scryptP = 1
+
+	// crcTable is a table that presents the polynomial we'll use for
+	// computing our checksum.
+	crcTable = crc32.MakeTable(crc32.Castagnoli)
+
+	// defaultPassphras is the default passphrase that will be used for
+	// encryption in the case that the user chooses not to specify their
+	// own passphrase.
+	defaultPassphrase = []byte("aezeed")
+)
+
+var (
+	// bitcoinGenesisDate is the timestamp of Bitcoin's genesis block.
+	// We'll use this value in order to create a compact birthday for the
+	// seed. The birthday will be interested as the number of days since
+	// the genesis date. We refer to this time period as ABE (after Bitcoin
+	// era).
+	bitcoinGenesisDate = time.Unix(1231006505, 0)
+)
+
+// CipherSeed is a fully decoded instance of the aezeed scheme. At a high
+// level, the encoded cipherseed is the enciphering of: a version byte, a set
+// of bytes for a timestamp, the entropy which will be used to directly
+// construct the HD seed, and finally a checksum over the rest. This scheme was
+// created as the widely used schemes in the space lack two critical traits: a
+// version byte, and a birthday timestamp. The version allows us to modify the
+// details of the scheme in the future, and the birthday gives wallets a limit
+// of how far back in the chain they'll need to start scanning. We also add an
+// external version to the enciphering plaintext seed. With this addition,
+// seeds are able to be "upgraded" (to diff params, or entirely diff crypt),
+// while maintaining the semantics of the plaintext seed.
+//
+// The core of the scheme is the usage of aez to carefully control the size of
+// the final encrypted seed. With the current parameters, this scheme can be
+// encoded using a 24 word mnemonic. We use 4 bytes of ciphertext expansion
+// when enciphering the raw seed, giving us the equivalent of 40-bit MAC (as we
+// check for a particular seed version). Using the external 4 byte checksum,
+// we're able to ensure that the user input the correct set of words.  Finally,
+// the password in the scheme is optional. If not specified, "aezeed" will be
+// used as the password. Otherwise, the addition of the password means that
+// users can encrypt the raw "plaintext" seed under distinct passwords to
+// produce unique mnemonic phrases.
+type CipherSeed struct {
+	// InternalVersion is the version of the plaintext cipherseed. This is
+	// to be used by wallets to determine if the seed version is compatible
+	// with the derivation schemes they know.
+	InternalVersion uint8
+
+	// Birthday is the time that the seed was created. This is expressed as
+	// the number of days since the timestamp in the Bitcoin genesis block.
+	// We use days as seconds gives us wasted granularity. The oldest seed
+	// that we can encode using this format is through the date 2188.
+	Birthday uint16
+
+	// Entropy is a set of bytes generated via a CSPRNG. This is the value
+	// that should be used to directly generate the HD root, as defined
+	// within BIP0032.
+	Entropy [EntropySize]byte
+
+	// salt is the salt that was used to generate the key from the user's
+	// specified passphrase.
+	salt [saltSize]byte
+}
+
+// New generates a new CipherSeed instance from an optional source of entropy.
+// If the entropy isn't provided, then a set of random bytes will be used in
+// place. The final argument should be the time at which the seed was created.
+func New(internalVersion uint8, entropy *[EntropySize]byte,
+	now time.Time) (*CipherSeed, error) {
+
+	// TODO(roasbeef): pass randomness source? to make fully determinsitc?
+
+	// If a set of entropy wasn't provided, then we'll read a set of bytes
+	// from the CSPRNG of our operating platform.
+	var seed [EntropySize]byte
+	if entropy == nil {
+		if _, err := rand.Read(seed[:]); err != nil {
+			return nil, err
+		}
+	} else {
+		// Otherwise, we'll copy the set of bytes.
+		copy(seed[:], entropy[:])
+	}
+
+	// To compute our "birthday", we'll first use the current time, then
+	// subtract that from the Bitcoin Genesis Date. We'll then convert that
+	// value to days.
+	birthday := uint16(now.Sub(bitcoinGenesisDate) / (time.Hour * 24))
+
+	c := &CipherSeed{
+		InternalVersion: internalVersion,
+		Birthday:        birthday,
+		Entropy:         seed,
+	}
+
+	// Next, we'll read a random salt that will be used with scrypt to
+	// eventually derive our key.
+	if _, err := rand.Read(c.salt[:]); err != nil {
+		return nil, err
+	}
+
+	return c, nil
+}
+
+// encode attempts to encode the target cipherSeed into the passed io.Writer
+// instance.
+func (c *CipherSeed) encode(w io.Writer) error {
+	err := binary.Write(w, binary.BigEndian, c.InternalVersion)
+	if err != nil {
+		return err
+	}
+
+	if err := binary.Write(w, binary.BigEndian, c.Birthday); err != nil {
+		return err
+	}
+
+	if _, err := w.Write(c.Entropy[:]); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// decode attempts to decode an encoded cipher seed instance into the target
+// CipherSeed struct.
+func (c *CipherSeed) decode(r io.Reader) error {
+	err := binary.Read(r, binary.BigEndian, &c.InternalVersion)
+	if err != nil {
+		return err
+	}
+
+	if err := binary.Read(r, binary.BigEndian, &c.Birthday); err != nil {
+		return err
+	}
+
+	if _, err := io.ReadFull(r, c.Entropy[:]); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// encodeAD returns the fully encoded associated data for use when performing
+// our current enciphering operation. The AD is: version || salt.
+func encodeAD(version uint8, salt [saltSize]byte) [adSize]byte {
+	var ad [adSize]byte
+	ad[0] = byte(version)
+	copy(ad[1:], salt[:])
+
+	return ad
+}
+
+// extractAD extracts an associated data from a fully encoded and enciphered
+// cipher seed.  This is to be used when attempting to decrypt an enciphered
+// cipher seed.
+func extractAD(encipheredSeed [EncipheredCipherSeedSize]byte) [adSize]byte {
+	var ad [adSize]byte
+	ad[0] = encipheredSeed[0]
+
+	copy(ad[1:], encipheredSeed[saltOffset:checkSumOffset])
+
+	return ad
+}
+
+// encipher takes a fully populated cipherseed instance, and enciphers the
+// encoded seed, then appends a randomly generated seed used to stretch the
+// passphrase out into an appropriate key, then computes a checksum over the
+// preceding.
+func (c *CipherSeed) encipher(pass []byte) ([EncipheredCipherSeedSize]byte, error) {
+	var cipherSeedBytes [EncipheredCipherSeedSize]byte
+
+	// If the passphrase wasn't provided, then we'll use the string
+	// "aezeed" in place.
+	passphrase := pass
+	if len(passphrase) == 0 {
+		passphrase = defaultPassphrase
+	}
+
+	// With our salt pre-generated, we'll now run the password through a
+	// KDF to obtain the key we'll use for encryption.
+	key, err := scrypt.Key(
+		passphrase, c.salt[:], scryptN, scryptR, scryptP, keyLen,
+	)
+	if err != nil {
+		return cipherSeedBytes, err
+	}
+
+	// Next, we'll encode the serialized plaintext cipherseed into a buffer
+	// that we'll use for encryption.
+	var seedBytes bytes.Buffer
+	if err := c.encode(&seedBytes); err != nil {
+		return cipherSeedBytes, err
+	}
+
+	// With our plaintext seed encoded, we'll now construct the AD that
+	// will be passed to the encryption operation. This ensures to
+	// authenticate both the salt and the external version.
+	ad := encodeAD(CipherSeedVersion, c.salt)
+
+	// With all items assembled, we'll now encipher the plaintext seed
+	// with our AD, key, and MAC size.
+	cipherSeed := seedBytes.Bytes()
+	cipherText := aez.Encrypt(
+		key, nil, [][]byte{ad[:]}, CipherTextExpansion, cipherSeed, nil,
+	)
+
+	// Finally, we'll pack the {version || ciphertext || salt || checksum}
+	// seed into a byte slice for encoding as a mnemonic.
+	cipherSeedBytes[0] = byte(CipherSeedVersion)
+	copy(cipherSeedBytes[1:saltOffset], cipherText)
+	copy(cipherSeedBytes[saltOffset:], c.salt[:])
+
+	// With the seed mostly assembled, we'll now compute a checksum all the
+	// contents.
+	checkSum := crc32.Checksum(cipherSeedBytes[:checkSumOffset], crcTable)
+
+	// With our checksum computed, we can finish encoding the full cipher
+	// seed.
+	var checkSumBytes [4]byte
+	binary.BigEndian.PutUint32(checkSumBytes[:], checkSum)
+	copy(cipherSeedBytes[checkSumOffset:], checkSumBytes[:])
+
+	return cipherSeedBytes, nil
+}
+
+// cipherTextToMnemonic converts the aez ciphertext appended with the salt to a
+// 24-word mnemonic pass phrase.
+func cipherTextToMnemonic(cipherText [EncipheredCipherSeedSize]byte) (Mnemonic, error) {
+	var words [NummnemonicWords]string
+
+	// First, we'll convert the ciphertext itself into a bitstream for easy
+	// manipulation.
+	cipherBits := bstream.NewBStreamReader(cipherText[:])
+
+	// With our bitstream obtained, we'll read 11 bits at a time, then use
+	// that to index into our word list to obtain the next word.
+	for i := 0; i < NummnemonicWords; i++ {
+		index, err := cipherBits.ReadBits(bitsPerWord)
+		if err != nil {
+			return words, nil
+		}
+
+		words[i] = defaultWordList[index]
+	}
+
+	return words, nil
+}
+
+// ToMnemonic maps the final enciphered cipher seed to a human readable 24-word
+// mnemonic phrase. The password is optional, as if it isn't specified aezeed
+// will be used in its place.
+func (c *CipherSeed) ToMnemonic(pass []byte) (Mnemonic, error) {
+	// First, we'll convert the valid seed triple into an aez cipher text
+	// with our KDF salt appended to it.
+	cipherText, err := c.encipher(pass)
+	if err != nil {
+		return Mnemonic{}, nil
+	}
+
+	// Now that we have our cipher text, we'll convert it into a mnemonic
+	// phrase.
+	return cipherTextToMnemonic(cipherText)
+}
+
+// Encipher maps the cipher seed to an aez ciphertext using an optional
+// passphrase.
+func (c *CipherSeed) Encipher(pass []byte) ([EncipheredCipherSeedSize]byte, error) {
+	return c.encipher(pass)
+}
+
+// Mnemonic is a 24-word passphrase as of CipherSeedVersion zero. This
+// passphrase encodes an encrypted seed triple (version, birthday, entropy).
+// Additionally, we also encode the salt used with scrypt to derive the key
+// that the cipher text is encrypted with, and the version which tells us how
+// to decipher the seed.
+type Mnemonic [NummnemonicWords]string
+
+// mnemonicToCipherText converts a 24-word mnemonic phrase into a 33 byte
+// cipher text.
+//
+// NOTE: This assumes that all words have already been checked to be amongst
+// our word list.
+func mnemonicToCipherText(mnemonic *Mnemonic) [EncipheredCipherSeedSize]byte {
+	var cipherText [EncipheredCipherSeedSize]byte
+
+	// We'll now perform the reverse mapping to that of
+	// cipherTextToMnemonic: we'll get the index of the word, then write
+	// out that index to the bit stream.
+	cipherBits := bstream.NewBStreamWriter(EncipheredCipherSeedSize)
+	for _, word := range mnemonic {
+		// Using the reverse word map, we'll locate the index of this
+		// word within the word list.
+		index := uint64(reverseWordMap[word])
+
+		// With the index located, we'll now write this out to the
+		// bitstream, appending to what's already there.
+		cipherBits.WriteBits(index, bitsPerWord)
+	}
+
+	copy(cipherText[:], cipherBits.Bytes())
+
+	return cipherText
+}
+
+// ToCipherSeed attempts to map the mnemonic to the original cipher text byte
+// slice. Then we'll attempt to decrypt the ciphertext using aez with the
+// passed passphrase, using the last 5 bytes of the ciphertext as a salt for
+// the KDF.
+func (m *Mnemonic) ToCipherSeed(pass []byte) (*CipherSeed, error) {
+	// First, we'll attempt to decipher the mnemonic by mapping back into
+	// our byte slice and applying our deciphering scheme.
+	plainSeed, err := m.Decipher(pass)
+	if err != nil {
+		return nil, err
+	}
+
+	// If decryption was successful, then we'll decode into a fresh
+	// CipherSeed struct.
+	var c CipherSeed
+	if err := c.decode(bytes.NewReader(plainSeed[:])); err != nil {
+		return nil, err
+	}
+
+	return &c, nil
+}
+
+// decipherCipherSeed attempts to decipher the passed cipher seed ciphertext
+// using the passed passphrase. This function is the opposite of
+// the encipher method.
+func decipherCipherSeed(cipherSeedBytes [EncipheredCipherSeedSize]byte,
+	pass []byte) ([DecipheredCipherSeedSize]byte, error) {
+
+	var plainSeed [DecipheredCipherSeedSize]byte
+
+	// Before we do anything, we'll ensure that the version is one that we
+	// understand. Otherwise, we won't be able to decrypt, or even parse
+	// the cipher seed.
+	if uint8(cipherSeedBytes[0]) != CipherSeedVersion {
+		return plainSeed, ErrIncorrectVersion
+	}
+
+	// Next, we'll slice off the salt from the pass cipher seed, then
+	// snip off the end of the cipher seed, ignoring the version, and
+	// finally the checksum.
+	salt := cipherSeedBytes[saltOffset : saltOffset+saltSize]
+	cipherSeed := cipherSeedBytes[1:saltOffset]
+	checksum := cipherSeedBytes[checkSumOffset:]
+
+	// Before we perform any crypto operations, we'll re-create and verify
+	// the checksum to ensure that the user input the proper set of words.
+	freshChecksum := crc32.Checksum(cipherSeedBytes[:checkSumOffset], crcTable)
+	if freshChecksum != binary.BigEndian.Uint32(checksum) {
+		return plainSeed, ErrIncorrectMnemonic
+	}
+
+	// With the salt separated from the cipher text, we'll now obtain the
+	// key used for encryption.
+	key, err := scrypt.Key(pass, salt, scryptN, scryptR, scryptP, keyLen)
+	if err != nil {
+		return plainSeed, err
+	}
+
+	// We'll also extract the AD that will be required to properly pass the
+	// MAC check.
+	ad := extractAD(cipherSeedBytes)
+
+	// With the key, we'll attempt to decrypt the plaintext. If the
+	// ciphertext was altered, or the passphrase is incorrect, then we'll
+	// error out.
+	plainSeedBytes, ok := aez.Decrypt(
+		key, nil, [][]byte{ad[:]}, CipherTextExpansion, cipherSeed, nil,
+	)
+	if !ok {
+		return plainSeed, ErrInvalidPass
+	}
+	copy(plainSeed[:], plainSeedBytes)
+
+	return plainSeed, nil
+
+}
+
+// Decipher attempts to decipher the encoded mnemonic by first mapping to the
+// original chipertext, then applying our deciphering scheme. ErrInvalidPass
+// will be returned if the passphrase is incorrect.
+func (m *Mnemonic) Decipher(pass []byte) ([DecipheredCipherSeedSize]byte, error) {
+
+	// Before we attempt to map the mnemonic back to the original
+	// ciphertext, we'll ensure that all the word are actually a part of
+	// the current default word list.
+	for _, word := range m {
+		if !strings.Contains(englishWordList, word) {
+			emptySeed := [DecipheredCipherSeedSize]byte{}
+			return emptySeed, ErrUnknownMnenomicWord{word}
+		}
+	}
+
+	// If the passphrase wasn't provided, then we'll use the string
+	// "aezeed" in place.
+	passphrase := pass
+	if len(passphrase) == 0 {
+		passphrase = defaultPassphrase
+	}
+
+	// Next, we'll map the mnemonic phrase back into the original cipher
+	// text.
+	cipherText := mnemonicToCipherText(m)
+
+	// Finally, we'll attempt to decipher the enciphered seed. The result
+	// will be the raw seed minus the ciphertext expansion, external
+	// version, and salt.
+	return decipherCipherSeed(cipherText, passphrase)
+}
+
+// ChangePass takes an existing mnemonic, and passphrase for said mnemonic and
+// re-enciphers the plaintext cipher seed into a brand new mnemonic. This can
+// be used to allow users to re-encrypt the same seed with multiple pass
+// phrases, or just change the passphrase on an existing seed.
+func (m *Mnemonic) ChangePass(oldPass, newPass []byte) (Mnemonic, error) {
+	var newmnemonic Mnemonic
+
+	// First, we'll try to decrypt the current mnemonic using the existing
+	// passphrase. If this fails, then we can't proceed any further.
+	cipherSeed, err := m.ToCipherSeed(oldPass)
+	if err != nil {
+		return newmnemonic, err
+	}
+
+	// If the deciperhing was successful, then we'll now re-encipher using
+	// the new user provided passphrase.
+	return cipherSeed.ToMnemonic(newPass)
+}

aezeed/cipherseeed_test.go

@@ -0,0 +1,513 @@
+package aezeed
+
+import (
+	"bytes"
+	"math/rand"
+	"testing"
+	"testing/quick"
+	"time"
+)
+
+var (
+	testEntropy = [EntropySize]byte{
+		0x81, 0xb6, 0x37, 0xd8,
+		0x63, 0x59, 0xe6, 0x96,
+		0x0d, 0xe7, 0x95, 0xe4,
+		0x1e, 0x0b, 0x4c, 0xfd,
+	}
+)
+
+func assertCipherSeedEqual(t *testing.T, cipherSeed *CipherSeed,
+	cipherSeed2 *CipherSeed) {
+
+	if cipherSeed.InternalVersion != cipherSeed2.InternalVersion {
+		t.Fatalf("mismatched versions: expected %v, got %v",
+			cipherSeed.InternalVersion, cipherSeed2.InternalVersion)
+	}
+	if cipherSeed.Birthday != cipherSeed2.Birthday {
+		t.Fatalf("mismatched birthday: expected %v, got %v",
+			cipherSeed.Birthday, cipherSeed2.Birthday)
+	}
+	if cipherSeed.Entropy != cipherSeed2.Entropy {
+		t.Fatalf("mismatched versions: expected %x, got %x",
+			cipherSeed.Entropy[:], cipherSeed2.Entropy[:])
+	}
+}
+
+func TestAezeedVersion0TestVectors(t *testing.T) {
+	t.Parallel()
+
+	// TODO(roasbeef):
+}
+
+// TestEmptyPassphraseDerivation tests that the aezeed scheme is able to derive
+// a proper mnemonic, and decipher that mnemonic when the user uses an empty
+// passphrase.
+func TestEmptyPassphraseDerivation(t *testing.T) {
+	t.Parallel()
+
+	// Our empty passphrase...
+	pass := []byte{}
+
+	// We'll now create a new cipher seed with an internal version of zero
+	// to simulate a wallet that just adopted the scheme.
+	cipherSeed, err := New(0, &testEntropy, time.Now())
+	if err != nil {
+		t.Fatalf("unable to create seed: %v", err)
+	}
+
+	// Now that the seed has been created, we'll attempt to convert it to a
+	// valid mnemonic.
+	mnemonic, err := cipherSeed.ToMnemonic(pass)
+	if err != nil {
+		t.Fatalf("unable to create mnemonic: %v", err)
+	}
+
+	// Next, we'll try to decrypt the mnemonic with the passphrase that we
+	// used.
+	cipherSeed2, err := mnemonic.ToCipherSeed(pass)
+	if err != nil {
+		t.Fatalf("unable to decrypt mnemonic: %v", err)
+	}
+
+	// Finally, we'll ensure that the uncovered cipher seed matches
+	// precisely.
+	assertCipherSeedEqual(t, cipherSeed, cipherSeed2)
+}
+
+// TestManualEntropyGeneration tests that if the user doesn't provide a source
+// of entropy, then we do so ourselves.
+func TestManualEntropyGeneration(t *testing.T) {
+	t.Parallel()
+
+	// Our empty passphrase...
+	pass := []byte{}
+
+	// We'll now create a new cipher seed with an internal version of zero
+	// to simulate a wallet that just adopted the scheme.
+	cipherSeed, err := New(0, nil, time.Now())
+	if err != nil {
+		t.Fatalf("unable to create seed: %v", err)
+	}
+
+	// Now that the seed has been created, we'll attempt to convert it to a
+	// valid mnemonic.
+	mnemonic, err := cipherSeed.ToMnemonic(pass)
+	if err != nil {
+		t.Fatalf("unable to create mnemonic: %v", err)
+	}
+
+	// Next, we'll try to decrypt the mnemonic with the passphrase that we
+	// used.
+	cipherSeed2, err := mnemonic.ToCipherSeed(pass)
+	if err != nil {
+		t.Fatalf("unable to decrypt mnemonic: %v", err)
+	}
+
+	// Finally, we'll ensure that the uncovered cipher seed matches
+	// precisely.
+	assertCipherSeedEqual(t, cipherSeed, cipherSeed2)
+}
+
+// TestInvalidPassphraseRejection tests if a caller attempts to use the
+// incorrect passprhase for an enciphered seed, then the proper error is
+// returned.
+func TestInvalidPassphraseRejection(t *testing.T) {
+	t.Parallel()
+
+	// First, we'll generate a new cipher seed with a test passphrase.
+	pass := []byte("test")
+	cipherSeed, err := New(0, &testEntropy, time.Now())
+	if err != nil {
+		t.Fatalf("unable to create seed: %v", err)
+	}
+
+	// Now that we have our cipher seed, we'll encipher it and request a
+	// mnemonic that we can use to recover later.
+	mnemonic, err := cipherSeed.ToMnemonic(pass)
+	if err != nil {
+		t.Fatalf("unable to create mnemonic: %v", err)
+	}
+
+	// If we try to decipher with the wrong passphrase, we should get the
+	// proper error.
+	wrongPass := []byte("kek")
+	if _, err := mnemonic.ToCipherSeed(wrongPass); err != ErrInvalidPass {
+		t.Fatalf("expected ErrInvalidPass, instead got %v", err)
+	}
+}
+
+// TestRawEncipherDecipher tests that callers are able to use the raw methods
+// to map between ciphertext and the raw plaintext deciphered seed.
+func TestRawEncipherDecipher(t *testing.T) {
+	t.Parallel()
+
+	// First, we'll generate a new cipher seed with a test passphrase.
+	pass := []byte("test")
+	cipherSeed, err := New(0, &testEntropy, time.Now())
+	if err != nil {
+		t.Fatalf("unable to create seed: %v", err)
+	}
+
+	// With the cipherseed obtained, we'll now use the raw encipher method
+	// to obtain our final cipher text.
+	cipherText, err := cipherSeed.Encipher(pass)
+	if err != nil {
+		t.Fatalf("unable to encipher seed: %v", err)
+	}
+
+	mnemonic, err := cipherTextToMnemonic(cipherText)
+	if err != nil {
+		t.Fatalf("unable to create mnemonic: %v", err)
+	}
+
+	// Now that we have the ciphertext (mapped to the mnemonic), we'll
+	// attempt to decipher it raw using the user's passphrase.
+	plainSeedBytes, err := mnemonic.Decipher(pass)
+	if err != nil {
+		t.Fatalf("unable to decipher: %v", err)
+	}
+
+	// If we deserialize the plaintext seed bytes, it should exactly match
+	// the original cipher seed.
+	var newSeed CipherSeed
+	err = newSeed.decode(bytes.NewReader(plainSeedBytes[:]))
+	if err != nil {
+		t.Fatalf("unable to decode cipher seed: %v", err)
+	}
+
+	assertCipherSeedEqual(t, cipherSeed, &newSeed)
+}
+
+// TestInvalidExternalVersion tests that if we present a ciphertext with the
+// incorrect version to decipherCipherSeed, then it fails with the expected
+// error.
+func TestInvalidExternalVersion(t *testing.T) {
+	t.Parallel()
+
+	// First, we'll generate a new cipher seed.
+	cipherSeed, err := New(0, &testEntropy, time.Now())
+	if err != nil {
+		t.Fatalf("unable to create seed: %v", err)
+	}
+
+	// With the cipherseed obtained, we'll now use the raw encipher method
+	// to obtain our final cipher text.
+	pass := []byte("newpasswhodis")
+	cipherText, err := cipherSeed.Encipher(pass)
+	if err != nil {
+		t.Fatalf("unable to encipher seed: %v", err)
+	}
+
+	// Now that we have the cipher text, we'll modify the first byte to be
+	// an invalid version.
+	cipherText[0] = 44
+
+	// With the version swapped, if we try to decipher it, (no matter the
+	// passphrase), it should fail.
+	_, err = decipherCipherSeed(cipherText, []byte("kek"))
+	if err != ErrIncorrectVersion {
+		t.Fatalf("wrong error: expected ErrIncorrectVersion, "+
+			"got %v", err)
+	}
+}
+
+// TestChangePassphrase tests that we're able to generate a cipher seed, then
+// change the password. If we attempt to decipher the new enciphered seed, then
+// we should get the exact same seed back.
+func TestChangePassphrase(t *testing.T) {
+	t.Parallel()
+
+	// First, we'll generate a new cipher seed with a test passphrase.
+	pass := []byte("test")
+	cipherSeed, err := New(0, &testEntropy, time.Now())
+	if err != nil {
+		t.Fatalf("unable to create seed: %v", err)
+	}
+
+	// Now that we have our cipher seed, we'll encipher it and request a
+	// mnemonic that we can use to recover later.
+	mnemonic, err := cipherSeed.ToMnemonic(pass)
+	if err != nil {
+		t.Fatalf("unable to create mnemonic: %v", err)
+	}
+
+	// Now that have the mnemonic, we'll attempt to re-encipher the
+	// passphrase in order to get a brand new mnemonic.
+	newPass := []byte("strongerpassyeh!")
+	newmnemonic, err := mnemonic.ChangePass(pass, newPass)
+	if err != nil {
+		t.Fatalf("unable to change passphrase: %v", err)
+	}
+
+	// We'll now attempt to decipher the new mnemonic using the new
+	// passphrase to arrive at (what should be) the original cipher seed.
+	newCipherSeed, err := newmnemonic.ToCipherSeed(newPass)
+	if err != nil {
+		t.Fatalf("unable to decipher cipher seed: %v", err)
+	}
+
+	// Now that we have the cipher seed, we'll verify that the plaintext
+	// seed matches *identically*.
+	assertCipherSeedEqual(t, cipherSeed, newCipherSeed)
+}
+
+// TestChangePassphraseWrongPass tests that if we have a valid enciphered
+// cipherseed, but then try to change the password with the *wrong* password,
+// then we get an error.
+func TestChangePassphraseWrongPass(t *testing.T) {
+	t.Parallel()
+
+	// First, we'll generate a new cipher seed with a test passphrase.
+	pass := []byte("test")
+	cipherSeed, err := New(0, &testEntropy, time.Now())
+	if err != nil {
+		t.Fatalf("unable to create seed: %v", err)
+	}
+
+	// Now that we have our cipher seed, we'll encipher it and request a
+	// mnemonic that we can use to recover later.
+	mnemonic, err := cipherSeed.ToMnemonic(pass)
+	if err != nil {
+		t.Fatalf("unable to create mnemonic: %v", err)
+	}
+
+	// Now that have the mnemonic, we'll attempt to re-encipher the
+	// passphrase in order to get a brand new mnemonic. However, we'll be
+	// using the *wrong* passphrase. This should result in an
+	// ErrInvalidPass error.
+	wrongPass := []byte("kek")
+	newPass := []byte("strongerpassyeh!")
+	_, err = mnemonic.ChangePass(wrongPass, newPass)
+	if err != ErrInvalidPass {
+		t.Fatalf("expected ErrInvalidPass, instead got %v", err)
+	}
+}
+
+// TestMnemonicEncoding uses quickcheck like property based testing to ensure
+// that we're always able to fully recover the original byte stream encoded
+// into the mnemonic phrase.
+func TestMnemonicEncoding(t *testing.T) {
+	t.Parallel()
+
+	// mainScenario is the main driver of our property based test. We'll
+	// ensure that given a random byte string of length 33 bytes, if we
+	// convert that to the mnemonic, then we should be able to reverse the
+	// conversion.
+	mainScenario := func(cipherSeedBytes [EncipheredCipherSeedSize]byte) bool {
+		mnemonic, err := cipherTextToMnemonic(cipherSeedBytes)
+		if err != nil {
+			t.Fatalf("unable to map cipher text: %v", err)
+			return false
+		}
+
+		newCipher := mnemonicToCipherText(&mnemonic)
+
+		if newCipher != cipherSeedBytes {
+			t.Fatalf("cipherseed doesn't match: expected %v, got %v",
+				cipherSeedBytes, newCipher)
+			return false
+		}
+
+		return true
+	}
+
+	if err := quick.Check(mainScenario, nil); err != nil {
+		t.Fatalf("fuzz check failed: %v", err)
+	}
+}
+
+// TestEncipherDecipher is a property-based test that ensures that given a
+// version, entropy, and birthday, then we're able to map that to a cipherseed
+// mnemonic, then back to the original plaintext cipher seed.
+func TestEncipherDecipher(t *testing.T) {
+	t.Parallel()
+
+	// mainScenario is the main driver of our property based test. We'll
+	// ensure that given a random seed tuple (internal version, entropy,
+	// and birthday) we're able to convert that to a valid cipher seed.
+	// Additionally, we should be able to decipher the final mnemonic, and
+	// recover the original cipherseed.
+	mainScenario := func(version uint8, entropy [EntropySize]byte,
+		nowInt int64, pass [20]byte) bool {
+
+		now := time.Unix(nowInt, 0)
+
+		cipherSeed, err := New(version, &entropy, now)
+		if err != nil {
+			t.Fatalf("unable to map cipher text: %v", err)
+			return false
+		}
+
+		mnemonic, err := cipherSeed.ToMnemonic(pass[:])
+		if err != nil {
+			t.Fatalf("unable to generate mnemonic: %v", err)
+			return false
+		}
+
+		cipherSeed2, err := mnemonic.ToCipherSeed(pass[:])
+		if err != nil {
+			t.Fatalf("unable to decrypt cipher seed: %v", err)
+			return false
+		}
+
+		if cipherSeed.InternalVersion != cipherSeed2.InternalVersion {
+			t.Fatalf("mismatched versions: expected %v, got %v",
+				cipherSeed.InternalVersion, cipherSeed2.InternalVersion)
+			return false
+		}
+		if cipherSeed.Birthday != cipherSeed2.Birthday {
+			t.Fatalf("mismatched birthday: expected %v, got %v",
+				cipherSeed.Birthday, cipherSeed2.Birthday)
+			return false
+		}
+		if cipherSeed.Entropy != cipherSeed2.Entropy {
+			t.Fatalf("mismatched versions: expected %x, got %x",
+				cipherSeed.Entropy[:], cipherSeed2.Entropy[:])
+			return false
+		}
+
+		return true
+	}
+
+	if err := quick.Check(mainScenario, nil); err != nil {
+		t.Fatalf("fuzz check failed: %v", err)
+	}
+}
+
+// TestSeedEncodeDecode tests that we're able to reverse the encoding of an
+// arbitrary raw seed.
+func TestSeedEncodeDecode(t *testing.T) {
+	// mainScenario is the primary driver of our property-based test. We'll
+	// ensure that given a random cipher seed, we can encode it an decode
+	// it precisely.
+	mainScenario := func(version uint8, nowInt int64,
+		entropy [EntropySize]byte) bool {
+
+		now := time.Unix(nowInt, 0)
+		seed := CipherSeed{
+			InternalVersion: version,
+			Birthday:        uint16(now.Sub(bitcoinGenesisDate) / (time.Hour * 24)),
+			Entropy:         entropy,
+		}
+
+		var b bytes.Buffer
+		if err := seed.encode(&b); err != nil {
+			t.Fatalf("unable to encode: %v", err)
+			return false
+		}
+
+		var newSeed CipherSeed
+		if err := newSeed.decode(&b); err != nil {
+			t.Fatalf("unable to decode: %v", err)
+			return false
+		}
+
+		if seed.InternalVersion != newSeed.InternalVersion {
+			t.Fatalf("mismatched versions: expected %v, got %v",
+				seed.InternalVersion, newSeed.InternalVersion)
+			return false
+		}
+		if seed.Birthday != newSeed.Birthday {
+			t.Fatalf("mismatched birthday: expected %v, got %v",
+				seed.Birthday, newSeed.Birthday)
+			return false
+		}
+		if seed.Entropy != newSeed.Entropy {
+			t.Fatalf("mismatched versions: expected %x, got %x",
+				seed.Entropy[:], newSeed.Entropy[:])
+			return false
+		}
+
+		return true
+	}
+
+	if err := quick.Check(mainScenario, nil); err != nil {
+		t.Fatalf("fuzz check failed: %v", err)
+	}
+}
+
+// TestDecipherUnknownMnenomicWord tests that if we obtain a mnemonic, the
+// modify one of the words to not be within the word list, then it's detected
+// when we attempt to map it back to the original cipher seed.
+func TestDecipherUnknownMnenomicWord(t *testing.T) {
+	t.Parallel()
+
+	// First, we'll create a new cipher seed with "test" ass a password.
+	pass := []byte("test")
+	cipherSeed, err := New(0, &testEntropy, time.Now())
+	if err != nil {
+		t.Fatalf("unable to create seed: %v", err)
+	}
+
+	// Now that we have our cipher seed, we'll encipher it and request a
+	// mnemonic that we can use to recover later.
+	mnemonic, err := cipherSeed.ToMnemonic(pass)
+	if err != nil {
+		t.Fatalf("unable to create mnemonic: %v", err)
+	}
+
+	// Before we attempt to decrypt the cipher seed, we'll mutate one of
+	// the word so it isn't actually in our final word list.
+	randIndex := rand.Int31n(int32(len(mnemonic)))
+	mnemonic[randIndex] = "kek"
+
+	// If we attempt to map back to the original cipher seed now, then we
+	// should get ErrUnknownMnenomicWord.
+	_, err = mnemonic.ToCipherSeed(pass)
+	if err == nil {
+		t.Fatalf("expected ErrUnknownMnenomicWord error")
+	}
+
+	wordErr, ok := err.(ErrUnknownMnenomicWord)
+	if !ok {
+		t.Fatalf("expected ErrUnknownMnenomicWord instead got %T", err)
+	}
+
+	if wordErr.word != "kek" {
+		t.Fatalf("word mismatch: expected %v, got %v", "kek", wordErr.word)
+	}
+}
+
+// TestDecipherIncorrectMnemonic tests that if we obtain a cipherseed, but then
+// swap out words, then checksum fails.
+func TestDecipherIncorrectMnemonic(t *testing.T) {
+	// First, we'll create a new cipher seed with "test" ass a password.
+	pass := []byte("test")
+	cipherSeed, err := New(0, &testEntropy, time.Now())
+	if err != nil {
+		t.Fatalf("unable to create seed: %v", err)
+	}
+
+	// Now that we have our cipher seed, we'll encipher it and request a
+	// mnemonic that we can use to recover later.
+	mnemonic, err := cipherSeed.ToMnemonic(pass)
+	if err != nil {
+		t.Fatalf("unable to create mnemonic: %v", err)
+	}
+
+	// We'll now swap out two words from the mnemonic, which should trigger
+	// a checksum failure.
+	swapIndex1 := 9
+	swapIndex2 := 13
+	mnemonic[swapIndex1], mnemonic[swapIndex2] = mnemonic[swapIndex2], mnemonic[swapIndex1]
+
+	// If we attempt to decrypt now, we should get a checksum failure.
+	// If we attempt to map back to the original cipher seed now, then we
+	// should get ErrUnknownMnenomicWord.
+	_, err = mnemonic.ToCipherSeed(pass)
+	if err != ErrIncorrectMnemonic {
+		t.Fatalf("expected ErrIncorrectMnemonic error")
+	}
+
+}
+
+// TODO(roasbeef): add test failure checksum fail is modified, new error
+
+func init() {
+	// For the purposes of our test, we'll crank down the scrypt params a
+	// bit.
+	scryptN = 16
+	scryptR = 8
+	scryptP = 1
+}

aezeed/errors.go

@@ -0,0 +1,30 @@
+package aezeed
+
+import "fmt"
+
+var (
+	// ErrIncorrectVersion is returned if a seed bares a mismatched
+	// external version to that of the package executing the aezeed scheme.
+	ErrIncorrectVersion = fmt.Errorf("wrong seed version")
+
+	// ErrInvalidPass is returned if the user enters an invalid passphrase
+	// for a particular enciphered mnemonic.
+	ErrInvalidPass = fmt.Errorf("invalid passphrase")
+
+	// ErrIncorrectMnemonic is returned if we detect that the checksum of
+	// the specified mnemonic doesn't match. This indicates the user input
+	// the wrong mnemonic.
+	ErrIncorrectMnemonic = fmt.Errorf("mnemonic phrase checksum doesn't" +
+		"match")
+)
+
+// ErrUnknownMnenomicWord is returned when attempting to decipher and
+// enciphered mnemonic, but a word encountered isn't a member of our word list.
+type ErrUnknownMnenomicWord struct {
+	word string
+}
+
+// Error returns a human readable string describing the error.
+func (e ErrUnknownMnenomicWord) Error() string {
+	return fmt.Sprintf("word %v isn't a part of default word list", e.word)
+}

glide.lock

@@ -1,6 +1,13 @@
-hash: b7b9aed5daf9b2fdc4083d310ab2cabfc86e08db6796b9301b2e2d73c9bd6174
+hash: 31c7557ef187f50de28557359e5179a47d5f4f153ec9b4f1ad264f771e7d1b5c
-updated: 2018-02-23T15:57:52.662879082-08:00
+updated: 2018-03-01T16:45:01.924542733-08:00
 imports:
+- name: git.schwanenlied.me/yawning/bsaes.git
+  version: e06297f34865a50b8e473105e52cb64ad1b55da8
+  subpackages:
+  - ct32
+  - ct64
+  - ghash
+  - internal/modes
 - name: github.com/aead/chacha20
   version: d31a916ded42d1640b9d89a26f8abd53cc96790c
   subpackages:
@@ -140,9 +147,12 @@ imports:
   version: 501572607d0273fc75b3b261fa4904d63f6ffa0e
 - name: github.com/urfave/cli
   version: cfb38830724cc34fedffe9a2a29fb54fa9169cd1
+- name: github.com/Yawning/aez
+  version: 4dad034d9db2caec23fb8f69b9160ae16f8d46a3
 - name: golang.org/x/crypto
   version: 49796115aa4b964c318aad4f3084fdb41e9aa067
   subpackages:
+  - blake2b
   - chacha20poly1305
   - curve25519
   - ed25519

glide.yaml

@@ -80,3 +80,7 @@ import:
 - package: github.com/rogpeppe/fastuuid
 - package: gopkg.in/errgo.v1
 - package: github.com/miekg/dns
+- package: github.com/Yawning/aez
+  version: 4dad034d9db2caec23fb8f69b9160ae16f8d46a3
+- package: github.com/kkdai/bstream
+  version: f391b8402d23024e7c0f624b31267a89998fca95