rc4

#ifndef RC4_H
#define RC4_H

#define KEYLEN256 256
class rc4
{
public:
    rc4();
    ~rc4();

    void swap(unsigned char *a, unsigned char *b);
    //initial state
    int KSA(unsigned char *S, unsigned char *K, int keylen);
    int KSA(unsigned char *K, int keylen);
    //keystream gen
    void PGRA(unsigned char *key, int plainlen);

//protected:
    unsigned char m_S[KEYLEN256];
};

#endif // RC4_H

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include "rc4.h"


rc4::rc4()
{
    memset(m_S, 0x00, sizeof(m_S));
    printf("rc4::rc4()\n");
}

rc4::~rc4()
{
    printf("rc4::~rc4()\n");
}

void rc4::swap(unsigned char *a, unsigned char *b)
{
    unsigned char tmp;
    tmp = *a;
    *a = *b;
    *b = tmp;
}

int rc4::KSA(unsigned char *S, unsigned char *K, int keylen)
{
        int i;
        //Temp is tmp vector
        unsigned char Temp[256] = {0};
        //init
        for (i = 0; i < KEYLEN256; ++i) {
            S[i] = i;
            Temp[i] = K[i % keylen];
        }

        //S initial seq
        int j=0;
        for (i = 0; i < KEYLEN256; ++i) {
            j = (j+S[i]+Temp[i]) % KEYLEN256;
            swap(&S[i], &S[j]);
        }
        return 0;
}

int rc4::KSA(unsigned char *K, int keylen)
{
    int i;
    //T is tmp vector
    unsigned char Temp[256] = {0};
    //init
    for (i = 0; i < KEYLEN256; ++i) {
        m_S[i] = i;
        Temp[i] = K[i % keylen];
    }

    //S initial seq
    int j=0;
    for (i = 0; i < KEYLEN256; ++i) {
        j = (j+m_S[i]+Temp[i]) % KEYLEN256;
        swap(&m_S[i], &m_S[j]);
    }
    return 0;
}

void rc4::PGRA(unsigned char *key, int plainlen)
{
    int i = 0, j = 0;
    int t=0;
    //*key = (uc *)malloc(sizeof(uc)*plainlen);
    for (int var = 0; var < plainlen; ++var) {
        i = (i+1) % KEYLEN256;
        j = (j+m_S[i]) % KEYLEN256;
        swap(&m_S[i], &m_S[j]);
        t=(m_S[i] + m_S[j]) % KEYLEN256;
        key[var]= m_S[t];
    }
}

//C v0.1 AC
#include<stdio.h>
#include <stdlib.h>
#include <string.h>
#include <alloca.h>
#include "rc4.h"
using namespace std;
typedef unsigned char uc;
int main(void)
{
    rc4 r4;
    uc key[] = "123a7872bef214518908d";
    uc buf[1024] = { 0 };
    uc ts[256] = { 0 };

    uc plain[] = "we are good friends";
    int plen = sizeof(plain);
    uc *tmpk = (uc *) malloc(sizeof(uc) * plen);

    int keylen = sizeof(key);
    r4.KSA((uc *) key, keylen);
    for (int var = 0; var < KEYLEN256; ++var) {
        ts[var] = r4.m_S[var];
        printf("%c", ts[var]);
    }
    printf("\ntmpk:\n");
    r4.PGRA(tmpk, plen);
    for (int var = 0; var < plen; ++var) {
        printf("%c", tmpk[var]);
    }
    printf("\n");
    printf("plain:%s\n", plain);
    printf("cipher:\n");

    for (int var = 0; var < plen; ++var) {
        buf[var] = tmpk[var] ^ plain[var];
        printf("%c", buf[var]);
    }
    printf("\n");
    for (int var = 0; var < plen; ++var) {
        printf("%c", tmpk[var] ^ buf[var]);
    }
    printf("\n");
       if (tmpk != NULL) {
       free(tmpk);
       tmpk = NULL;
       }

    return 0;
}