/** Convert mnemonic word list to original entropy value. */
public byte[] toEntropy(List<String> words)
throws MnemonicException.MnemonicLengthException, MnemonicException.MnemonicWordException,
MnemonicException.MnemonicChecksumException {
if (words.size() % 3 > 0)
throw new MnemonicException.MnemonicLengthException(
"Word list size must be multiple of three words.");
if (words.size() == 0)
throw new MnemonicException.MnemonicLengthException("Word list is empty.");
// Look up all the words in the list and construct the
// concatenation of the original entropy and the checksum.
//
int concatLenBits = words.size() * 11;
boolean[] concatBits = new boolean[concatLenBits];
int wordindex = 0;
for (String word : words) {
// Find the words index in the wordlist.
int ndx = Collections.binarySearch(this.wordList, word);
if (ndx < 0) throw new MnemonicException.MnemonicWordException(word);
// Set the next 11 bits to the value of the index.
for (int ii = 0; ii < 11; ++ii)
concatBits[(wordindex * 11) + ii] = (ndx & (1 << (10 - ii))) != 0;
++wordindex;
}
int checksumLengthBits = concatLenBits / 33;
int entropyLengthBits = concatLenBits - checksumLengthBits;
// Extract original entropy as bytes.
byte[] entropy = new byte[entropyLengthBits / 8];
for (int ii = 0; ii < entropy.length; ++ii)
for (int jj = 0; jj < 8; ++jj) if (concatBits[(ii * 8) + jj]) entropy[ii] |= 1 << (7 - jj);
// Take the digest of the entropy.
byte[] hash = Sha256Hash.create(entropy).getBytes();
boolean[] hashBits = bytesToBits(hash);
// Check all the checksum bits.
for (int i = 0; i < checksumLengthBits; ++i)
if (concatBits[entropyLengthBits + i] != hashBits[i])
throw new MnemonicException.MnemonicChecksumException();
return entropy;
}
/** Convert entropy data to mnemonic word list. */
public List<String> toMnemonic(byte[] entropy) throws MnemonicException.MnemonicLengthException {
if (entropy.length % 4 > 0)
throw new MnemonicException.MnemonicLengthException(
"Entropy length not multiple of 32 bits.");
if (entropy.length == 0)
throw new MnemonicException.MnemonicLengthException("Entropy is empty.");
// We take initial entropy of ENT bits and compute its
// checksum by taking first ENT / 32 bits of its SHA256 hash.
byte[] hash = Sha256Hash.create(entropy).getBytes();
boolean[] hashBits = bytesToBits(hash);
boolean[] entropyBits = bytesToBits(entropy);
int checksumLengthBits = entropyBits.length / 32;
// We append these bits to the end of the initial entropy.
boolean[] concatBits = new boolean[entropyBits.length + checksumLengthBits];
System.arraycopy(entropyBits, 0, concatBits, 0, entropyBits.length);
System.arraycopy(hashBits, 0, concatBits, entropyBits.length, checksumLengthBits);
// Next we take these concatenated bits and split them into
// groups of 11 bits. Each group encodes number from 0-2047
// which is a position in a wordlist. We convert numbers into
// words and use joined words as mnemonic sentence.
ArrayList<String> words = new ArrayList<String>();
int nwords = concatBits.length / 11;
for (int i = 0; i < nwords; ++i) {
int index = 0;
for (int j = 0; j < 11; ++j) {
index <<= 1;
if (concatBits[(i * 11) + j]) index |= 0x1;
}
words.add(this.wordList.get(index));
}
return words;
}
public static ByteString hashToByteString(Sha256Hash hash) {
return ByteString.copyFrom(hash.getBytes());
}
