/// <summary>
/// Verifies the mnemonic phrase's word sequence checksum is valid.
/// </summary>
/// <returns>Returns true if the mnemonic word sequence is valid.</returns>
public bool Verify()
{
// Verify our index count/word count is in our bounds.
if (Indices.Length < MNEMONIC_WORDS_MINIMUM && Indices.Length > MNEMONIC_WORDS_MAXIMUM)
{
return(false);
}
// Determine the size of our entropy and checksum in bits.
int bitStreamLength = Indices.Length * MNEMONIC_WORD_INDEX_BITCOUNT;
int checksumBitcount = bitStreamLength / (MNEMONIC_ENTROPY_BITS_PER_CHECKSUM_BIT + 1);
int entropyBitcount = checksumBitcount * MNEMONIC_ENTROPY_BITS_PER_CHECKSUM_BIT;
// Now we'll want to write the indices back to a bitstream to parse our entropy/checksum from it.
BitStream bitStream = new BitStream();
for (int i = 0; i < Indices.Length; i++)
{
// If our index is negative, return false
if (Indices[i] < 0)
{
return(false);
}
// Write the word index.
bitStream.Write((ulong)Indices[i], MNEMONIC_WORD_INDEX_BITCOUNT);
}
// Move back to the start of the data
bitStream.Position = 0;
bitStream.BitPosition = 0;
// Read our entropy data.
byte[] entropy = bitStream.ReadBytes(entropyBitcount, true);
// Read our checksum
byte[] checksum = bitStream.ReadBytes(checksumBitcount, true);
// Recalculate our hash of the entropy and derive our checksum from its bits sequentially.
byte[] calculatedChecksum = sha256Provider.ComputeHash(entropy);
bitStream.ClearContents();
bitStream.WriteBytes(calculatedChecksum, checksumBitcount);
// Move back to the start of the data
bitStream.Position = 0;
bitStream.BitPosition = 0;
// Read our calculated checksum.
calculatedChecksum = bitStream.ReadBytes(checksumBitcount, true);
// Close the bitstream.
bitStream.Close();
// Compare our sequences.
return(checksum.SequenceEqual(calculatedChecksum));
}
