1 /* rc5.c a C implementation of RC5 for AVR microcontrollers
4 * email: daniel.otte@rub.de
7 * this implementation is limited to 64bit blocks and a maximum of 255 rounds
12 #include <stdlib.h> /* malloc() & free() */
13 #include <string.h> /* memset() & memcpy() */
17 #define A (((uint32_t*)buffer)[0])
18 #define B (((uint32_t*)buffer)[1])
19 #define ROTL32(v,n) (((v)<<(n))|((v)>>(32-(n))))
20 #define ROTR32(v,n) (((v)>>(n))|((v)<<(32-(n))))
22 void rc5_enc(void* buffer, const rc5_ctx_t* ctx){
26 for(i=0; i<ctx->rounds; ++i){
27 A = ROTL32(A^B, B&31) + ctx->s[(i+1)*2+0];
28 B = ROTL32(A^B, A&31) + ctx->s[(i+1)*2+1];
32 void rc5_dec(void* buffer, const rc5_ctx_t* ctx){
34 for(i=ctx->rounds; i>0; --i){
35 B = ROTR32(B - ctx->s[i*2+1], A&31) ^ A;
36 A = ROTR32(A - ctx->s[i*2+0], B&31) ^ B;
42 P32 = 10110111111000010101000101100011 = b7e15163
43 Q32 = 10011110001101110111100110111001 = 9e3779b9
45 #define P32 0xb7e15163
46 #define Q32 0x9e3779b9
49 void rc5_init(void* key, uint16_t keysize_b, uint8_t rounds, rc5_ctx_t* ctx){
51 uint32_t a,b,l[(keysize_b+31)/32];
55 ctx->s = malloc(t*sizeof(uint32_t));
57 memset(l, 0, sizeof(uint32_t)*c);
58 memcpy(l, key, (keysize_b+7)/8);
62 ctx->s[i] = ctx->s[i-1] + Q32;
69 a=ctx->s[i]=ROTL32(ctx->s[i]+a+b, 3);
70 b=l[j]=ROTL32(l[j]+a+b, (a+b)&31);
76 void rc5_free(rc5_ctx_t* ctx){