#include <iostream>
#include <fstream>
#include <cstring>
using namespace std;
typedef unsigned long int WORD; /* Should be 32-bit = 4 bytes */
#define w 32 /* word size in bits */
#define r 12 /* number of rounds */
#define b 16 /* number of bytes in key */
#define c 4 /* number words in key */
/* c = max(1,ceil(8*b/w)) */
#define t 26 /* size of table S = 2*(r+1) words */
WORD S [t],L[c]; /* expanded key table */
WORD P = 0xb7e15163, Q = 0x9e3779b9; /* magic constants */
/* Rotation operators. x must be unsigned, to get logical right shift*/
#define ROTL(x,y) (((x)<<(y&(w-1))) | ((x)>>(w-(y&(w-1)))))
#define ROTR(x,y) (((x)>>(y&(w-1))) | ((x)<<(w-(y&(w-1)))))
void RC5_ENCRYPT(WORD *pt, WORD *ct) /* 2 WORD input pt/output ct */
{ WORD i, A=pt[0]+S[0], B=pt[1]+S[1];
for (i=1; i<=r; i++)
{ A = ROTL(A^B,B)+S[2*i];
B = ROTL(B^A,A)+S[2*i+1];
}
ct [0] = A ;
ct [1] = B ;
}
void RC5_DECRYPT(WORD *ct, WORD *pt) /* 2 WORD input ct/output pt */
{ WORD i, B=ct[1], A=ct[ 0];
for (i=r; i>0; i--)
{ B = ROTR(B-S [2*i+1],A)^A;
A = ROTR(A-S [2*i],B)^B;
}
pt [1] = B-S [1] ;pt [0] = A-S [0];
}
void RC5_SETUP(unsigned char *K) /* secret input key K 0...b-1] */
{ WORD i, j, k, u=w/8, A, B, L [c];
/* Initialize L, then S, then mix key into S */
for (i=b-1,L[c-1]=0; i!=-1; i--) L[i/u] = (L[i/u]<<8)+K[ i];
for (S [0]=P,i=1; i<t; i++) S [i] = S [i-1]+Q;
for (A=B=i=j=k=0; k<3*t; k++,i=(i+1)%t,j=(j+1)%c) /* 3*t > 3*c */
{ A = S[i] = ROTL(S [i]+(A+B),3);
B = L[j] = ROTL(L[j]+(A+B),(A+B));
}
}
void printword(WORD A)
{ WORD k;
for (k=0 ;k<w; k+=8) printf("%c");
}
int main()
{
WORD i, j, k,ptext, pt1 [2], pt2 [2], ct [2] = {0,0};
ifstream in("key1.txt");
ifstream in1("plt.txt");
ofstream out1("cpt.txt");
if(!in)
{
cout << "Cannot open file.\n";
return 1;
}
if(!in1)
{
cout << "Cannot open file.\n";
return 1;
}
unsigned char key[b];
in >> key;
in1 >> pt1[0];
in1 >> pt1[0];
if (sizeof(WORD)!=4)
printf("RC5 error: WORD has %d bytes.\n",sizeof(WORD));
RC5_SETUP(key);
RC5_ENCRYPT(pt1,ct);
printf("\n plaintext "); printword(pt1 [0]); printword(pt1 [1]);
printf(" ---> ciphertext "); printword(ct [0]); printword(ct [1]);
printf("\n");
RC5_SETUP(key);
RC5_DECRYPT(ct,pt2);
out1<<ct[0];
out1<<ct[1];
out1 <<"\n";
printf("\n plaintext "); printword(pt1 [0]); printword(pt1 [1]);
return 0;
}
Let the plt.txt file contain
101
100
let the key be
111
