Example #1
0
bool CMnemonic::Check(SecureString mnemonic)
{
    if (mnemonic.empty()) {
        return false;
    }

    uint32_t nWordCount{};

    for (size_t i = 0; i < mnemonic.size(); ++i) {
        if (mnemonic[i] == ' ') {
            nWordCount++;
        }
    }
    nWordCount++;
    // check number of words
    if (nWordCount != 12 && nWordCount != 18 && nWordCount != 24) {
        return false;
    }

    SecureString ssCurrentWord;
    SecureVector bits(32 + 1);

    uint32_t nWordIndex, ki, nBitsCount{};

    for (size_t i = 0; i < mnemonic.size(); ++i)
    {
        ssCurrentWord = "";
        while (i + ssCurrentWord.size() < mnemonic.size() && mnemonic[i + ssCurrentWord.size()] != ' ') {
            if (ssCurrentWord.size() >= 9) {
                return false;
            }
            ssCurrentWord += mnemonic[i + ssCurrentWord.size()];
        }
        i += ssCurrentWord.size();
        nWordIndex = 0;
        for (;;) {
            if (!wordlist[nWordIndex]) { // word not found
                return false;
            }
            if (ssCurrentWord == wordlist[nWordIndex]) { // word found on index nWordIndex
                for (ki = 0; ki < 11; ki++) {
                    if (nWordIndex & (1 << (10 - ki))) {
                        bits[nBitsCount / 8] |= 1 << (7 - (nBitsCount % 8));
                    }
                    nBitsCount++;
                }
                break;
            }
            nWordIndex++;
        }
    }
    if (nBitsCount != nWordCount * 11) {
        return false;
    }
    bits[32] = bits[nWordCount * 4 / 3];
    CSHA256().Write(&bits[0], nWordCount * 4 / 3).Finalize(&bits[0]);

    bool fResult = 0;
    if (nWordCount == 12) {
        fResult = (bits[0] & 0xF0) == (bits[32] & 0xF0); // compare first 4 bits
    } else
    if (nWordCount == 18) {
        fResult = (bits[0] & 0xFC) == (bits[32] & 0xFC); // compare first 6 bits
    } else
    if (nWordCount == 24) {
        fResult = bits[0] == bits[32]; // compare 8 bits
    }

    return fResult;
}