Function ff_asfcrypt_dec

libavformat/asfcrypt.c:148–196

}

void ff_asfcrypt_dec(const uint8_t key[20], uint8_t *data, int len)
{
    struct AVDES *des;
    struct AVRC4 *rc4;
    int num_qwords      = len >> 3;
    uint8_t *qwords     = data;
    uint64_t rc4buff[8] = { 0 };
    uint64_t packetkey;
    uint32_t ms_keys[12];
    uint64_t ms_state;
    int i;
    if (len < 16) {
        for (i = 0; i < len; i++)
            data[i] ^= key[i];
        return;
    }
    des = av_des_alloc();
    rc4 = av_rc4_alloc();
    if (!des || !rc4) {
        av_freep(&des);
        av_freep(&rc4);
        return;
    }

    av_rc4_init(rc4, key, 12 * 8, 1);
    av_rc4_crypt(rc4, (uint8_t *)rc4buff, NULL, sizeof(rc4buff), NULL, 1);
    multiswap_init((uint8_t *)rc4buff, ms_keys);

    packetkey  = AV_RN64(&qwords[num_qwords * 8 - 8]);
    packetkey ^= rc4buff[7];
    av_des_init(des, key + 12, 64, 1);
    av_des_crypt(des, (uint8_t *)&packetkey, (uint8_t *)&packetkey, 1, NULL, 1);
    packetkey ^= rc4buff[6];

    av_rc4_init(rc4, (uint8_t *)&packetkey, 64, 1);
    av_rc4_crypt(rc4, data, data, len, NULL, 1);

    ms_state = 0;
    for (i = 0; i < num_qwords - 1; i++, qwords += 8)
        ms_state = multiswap_enc(ms_keys, ms_state, AV_RL64(qwords));
    multiswap_invert_keys(ms_keys);
    packetkey = (packetkey << 32) | (packetkey >> 32);
    packetkey = av_le2ne64(packetkey);
    packetkey = multiswap_dec(ms_keys, ms_state, packetkey);
    AV_WL64(qwords, packetkey);

    av_free(rc4);
    av_free(des);
}