keeloq.c

#include "keeloq.h"

uint8_t nlf(uint8_t d)
{
    return (((uint32_t)(NLF_LOOKUP_CONSTANT) >> d) & 0x1);
}

void keeloq_encrypt(uint8_t *key, uint32_t *data, const uint16_t nrounds)
{
    uint32_t x;
    uint16_t loop;
    uint8_t o, nlf_input,k,ki;

    for (loop = 0; loop < nrounds; loop++)
    {
        nlf_input = (((*data >> 31) & 0x1) << 4) | (((*data >> 26) & 0x1) << 3) |
                    (((*data >> 20) & 0x1) << 2) | (((*data >> 9) & 0x1) << 1) | ((*data >> 1) & 0x1);

        o = nlf(nlf_input);
        ki=loop % 64;
        k=key[ki/8]>>(ki%8);
        x =k ^ (*data >> 16) ^ *data ^ o;
        *data = (*data >> 1) | (x << 31);
    }
}

void keeloq_decrypt(uint8_t *key, uint32_t *data,const uint16_t nrounds)
{
    uint32_t x;
    uint16_t loop;
    uint8_t o, nlf_input,k,ki;

    for (loop = 0; loop < nrounds; loop++)
    {
        nlf_input = (((*data >> 30) & 0x1) << 4) | (((*data >> 25) & 0x1) << 3) |
                    (((*data >> 19) & 0x1) << 2) | (((*data >> 8) & 0x1) << 1) | (*data & 0x1);

        o = nlf(nlf_input);
        ki=(uint16_t)(15 - loop) % 64;
        k=key[ki/8]>>(ki%8);
        x = k ^ (*data >> 31) ^ (*data >> 15) ^ o;
        *data = (*data << 1) | x&1;
    }
}