Method pseudorandomFunction

src/jlsrtp.cpp:66–196

}

int JLSRTP::pseudorandomFunction(std::vector<unsigned char> iv, int n, std::vector<unsigned char> &output)
{
    int rc = 0;
    unsigned int num_loops = 0;
    std::vector<unsigned char> block;
    std::vector<unsigned char> input;
    unsigned int ivSize = 0;
    unsigned int keySize = 0;
    int retVal = 0;

    switch (_active_crypto)
    {
        case PRIMARY_CRYPTO:
        {
            ivSize = iv.size();
            keySize = _primary_crypto.master_key.size();

            assert(ivSize == JLSRTP_SALTING_KEY_LENGTH);
            assert(keySize == JLSRTP_ENCRYPTION_KEY_LENGTH);
            if (ivSize == JLSRTP_SALTING_KEY_LENGTH)
            {
                if (keySize == JLSRTP_ENCRYPTION_KEY_LENGTH)
                {
                    input.resize(AES_BLOCK_SIZE);
                    output.clear();

                    // Determine how many AES_BLOCK_SIZE-byte encryption loops will be necessary to achieve at least n/8 bytes of pseudorandom ciphertext
                    num_loops = (n % JLSRTP_PSEUDORANDOM_BITS) ? ((n / JLSRTP_PSEUDORANDOM_BITS) + 1) : (n / JLSRTP_PSEUDORANDOM_BITS);

                    // Set encryption key
                    rc = setAESPseudoRandomFunctionKey(_active_crypto);
                    if (rc == 0)
                    {
                        // Reset IV/counter state
                        resetPseudoRandomState(iv);

                        for (unsigned int i = 0; i < num_loops; i++)
                        {
                            // Encrypt given _pseudorandomstate.ivec input using aes_key to block
                            block.clear();
                            block.resize(AES_BLOCK_SIZE);
                            AES_ctr128_pseudorandom_EVPencrypt(input.data(), block.data(), AES_BLOCK_SIZE, _pseudorandomstate.ivec, _pseudorandomstate.ecount, &_pseudorandomstate.num);
                            output.insert(output.end(), block.begin(), block.end());
                        }

                        // Truncate output to n/8 bytes
                        output.resize(n / 8);

                        retVal = 0;
                    }
                    else
                    {
                        retVal = -3;
                    }
                }
                else
                {
                    retVal = -2;