Subversion Repositories hf-risc

#include <hf-risc.h>

/*

XTEA encryption algorithm

based on reference code released into the public domain by David Wheeler and Roger Needham

the code takes 64 bits of data in v[0] and v[1] and 128 bits of key in key[0] - key[3]

recommended number of rounds is 32 (2 Feistel-network rounds are performed on each iteration).

*/

const uint32_t xtea_key[4] = {0xf0e1d2c3, 0xb4a59687, 0x78695a4b, 0x3c2d1e0f};

void encipher(uint32_t num_rounds, uint32_t v[2], uint32_t const key[4]){

        uint32_t i;

        uint32_t v0 = v[0], v1 = v[1], sum = 0, delta = 0x9E3779B9;

        for (i = 0; i < num_rounds; i++){

                v0 += (((v1 << 4) ^ (v1 >> 5)) + v1) ^ (sum + key[sum & 3]);

                sum += delta;

                v1 += (((v0 << 4) ^ (v0 >> 5)) + v0) ^ (sum + key[(sum>>11) & 3]);

        }

        v[0] = v0; v[1] = v1;

}

void decipher(uint32_t num_rounds, uint32_t v[2], uint32_t const key[4]){

        uint32_t i;

        uint32_t v0 = v[0], v1 = v[1], delta = 0x9E3779B9, sum = delta * num_rounds;

        for (i = 0; i < num_rounds; i++){

                v1 -= (((v0 << 4) ^ (v0 >> 5)) + v0) ^ (sum + key[(sum>>11) & 3]);

                sum -= delta;

                v0 -= (((v1 << 4) ^ (v1 >> 5)) + v1) ^ (sum + key[sum & 3]);

        }

        v[0] = v0; v[1] = v1;

}

int main(void){

        int msg[2] = {0x12345678, 0x90123456};

        int cycles;

        printf("message: %8x%8x\n", msg[0], msg[1]);

        cycles = COUNTER;

        encipher(32, msg, xtea_key);

        cycles = COUNTER - cycles;

        printf("encipher: %8x%8x, %d cycles\n", msg[0], msg[1], cycles);

        cycles = COUNTER;

        decipher(32, msg, xtea_key);

        cycles = COUNTER - cycles;

        printf("decipher: %8x%8x, %d cycles\n", msg[0], msg[1], cycles);

        return 0;

}