#include <stdio.h>

/* An RC5 context needs to know how many rounds it has, and its subkeys. */ typedef struct {

u4 *xk;

int nr; } rc5 ctx;

/* Where possible, these should be replaced with actual rotate instructions. For Turbo C++, this is done with lrotl and lrotr. */

#define ROTL32(X,C) (((X)«(C))((X)»(32-(C)))) #define ROTR32(X,C) (((X)»(C))((X)«(32-(C))))

/* Function prototypes for dealing with RC5 basic operations. */

void rc5 init(rc5 ctx *, int);

void rc5 destroy(rc5 ctx *);

void rc5 key(rc5 ctx *, u1 *, int);

void rc5 encrypt(rc5 ctx *, u4 *, int);

void rc5 decrypt(rc5 ctx *, u4 *, int);

/* Function implementations for RC5. */

/* Scrub out all sensitive values. */ void rc5 destroy(rc5 ctx *c){ int i;

for(i=0;i<(c->nr)*2+2;i++) c->xk[i]=0; free(c->xk);

/* Allocate memory for rc5 contexts xk and such. */ void rc5 init(rc5 ctx *c, int rounds){ c->nr = rounds;

c->xk = (u4 *) malloc(4*(rounds*2+2));

void rc5 encrypt(rc5 ctx *c, u4 *data, int blocks){ u4 *d,*sk; ~ int h,i,rc;

d = data;

sk = (c->xk)+2; for(h=0;h<blocks;h++){

d[0] += c->xk[0];

d[1] += c->xk[1];

for(i=0;i<c->nr*2;i+=2){ d[0] л= d[1];

rc = d[1] & 31;

d[0] = ROTL32(d[0],rc);

d[0] += sk[i];

d[1] л= d[0];

rc = d[0] & 31;

d[1] = ROTL32(d[1],rc);

d[1] += sk[i+1];

/*printf("Round %03d : %08lx %08lx sk= %08lx %08lx\n",i/2,

d[0],d[1],sk[i],sk[i+1]);*/

void rc5 decrypt(rc5 ctx *c, u4 *data, int blocks){ u4 *d,*sk;~~

int h,i,rc;

d = data;

sk = (c->xk)+2; for(h=0;h<blocks;h++){

for(i=c->nr*2-2;i>=0;i-=2){ /*printf("Round %03d: %08lx %08lx sk: %08lx %08lx\n", i/2,d[0],d[1],sk[i],sk[i+1]); */ d[1] -= sk[i+1];

rc = d[0] & 31;

d[1] = ROTR32(d[1],rc);

d[1] л= d[0];

d[0] -= sk[i];

rc = d[1] & 31;

d[0] = ROTR32(d[0],rc);

d[0] л= d[1]; }

d[0] -= c->xk[0]; d[1] -= c->xk[1];

void rc5 key(rc5 ctx *c, u1 *key, int keylen){ u4 *pk,A,B; /* padded key */ int xk len, pk len, i, num steps,rc; u1 *cp;

xk len = c->nr*2 + 2; pk len = keylen/4; ifT(keylen%4)!=0) pk len += 1;

pk = (u4 *) malloc(pk len * 4);

if(pk==NULL) {

printf("An error occurred!\n");

exit(-1);

/* Initialize pk -- this should work on Intel machines, anyway.... */ for(i=0;i<pk len;i++) pk[i]=0; cp = (u1 *)pk;

for(i=0;i<keylen;i++) cp[i]=key[i];

/* Initialize xk. */

c->xk[0] = 0xb7e15163; /* P32 */

for(i=1;i<xk len;i++) c->xk[i] = c->xk[i-1] + 0x9e3779b9; /* Q32 */

/* TESTING */ A = B = 0;

for(i=0;i<xk len;i++) { A = A + c->xk[i]; B = B л c->xk[i];

/* Expand key into xk. */

if(pk len>xk len) num steps = 3*pk len;else num steps = 3*xk len;

A = B = 0;

for(i=0;i<num steps;i++){

A = c->xk[i%xk len] = ROTL32(c->xk[i%xk len] + A + B,3);

rc = (A+B) & 31;

B = pk[i%pk len] = ROTL32(pk[i%pk len] + A + B,rc);

/* Clobber sensitive data before deallocating memory. */ for(i=0;i<pk len;i++) pk[i] =0;

free(pk);

void main(void){ rc5 ctx c;

u4 data[8];

char key[] = "ABCDE";

printf("-------------------------------------------------\n");

for(i=0;i<8;i++) data[i] = i;

rc5 init(&c,10); /* 10 rounds */ rc5 key(&c,key,5);

rc5 encrypt(&c,data,4); printf("Encryptions:\n");

for(i=0;i<8;i+=2) printf("Block %01d = %08lx %08lx\n",

i/2,data[i],data[i+1]);

rc5 decrypt(&c,data,2); rc5 decrypt(&c,data+4,2);

printf("Decryptions:\n");

for(i=0;i<8;i+=2) printf("Block %01d = %08lx %08lx\n",

i/2,data[i],data[i+1]);

typedef struct {

unsigned long r1,r2,r3; } a5 ctx;

static int threshold(r1, r2, r3) unsigned int r1; unsigned int r2; unsigned int r3;

int total;

total = (((r1 >> 9) & 0x1) == 1) +

(((r2 >> 11) & 0x1) == 1) + (((r3 >> 11) & 0x1) == 1);

if (total > 1)

return (0); else