public static byte[] GenerateEntropyFromWords(string[] words, Wordlist wordList)
{
// Should always have at least 12 words
if (words.Length % 3 > 0 || words.Length == 0)
{
throw new FormatException("Word list size must be a multiple of three words");
}
int concatLenBits = words.Length * 11;
Array concatBits = Array.CreateInstance(typeof(bool), concatLenBits);
int[] wordIndices = wordList.ToIndices(words);
int wordindex = 0;
foreach (int wordIndice in wordIndices)
{
// 11 bits per word (2048)
for (int i = 0; i < 11; ++i)
{
bool bit = (wordIndice & (1 << (10 - i))) != 0;
concatBits.SetValue(bit, (wordindex * 11) + i);
}
++wordindex;
}
int checksumLengthBits = concatLenBits / 33;
int entropyLengthBits = concatLenBits - checksumLengthBits;
byte[] entropy = new byte[entropyLengthBits / 8];
for (int i = 0; i < entropy.Length; ++i)
{
// 8 bits per byte...
for (int j = 0; j < 8; ++j)
{
bool bit = (bool)concatBits.GetValue((i * 8) + j);
if (bit)
{
entropy[i] |= (byte)(1 << (7 - j));
}
}
}
byte[] hash = SHA256.Create().ComputeHash(entropy);
BitArray hashBitArray = new BitArray(BytesToBoolArray(hash));
Array hashBits = Array.CreateInstance(typeof(bool), checksumLengthBits);
for (int i = 0; i < checksumLengthBits; i++)
{
hashBits.SetValue(hashBitArray.Get(i), i);
}
for (int i = 0; i < checksumLengthBits; ++i)
{
bool concatbit = (bool)concatBits.GetValue(entropyLengthBits + i);
bool hashbit = (bool)hashBits.GetValue(i);
if (concatbit != hashbit)
{
throw new Bip39CrcException("CRC Checksum validation failed");
}
}
return(entropy);
}
