Rc4算法加密-白红宇

Rc4算法加密

阅读量：6425 次

发布时间：2019-06-23

本文共 2964 字，大约阅读时间需要 9 分钟。

+(NSString*)HloveyRC4:(NSString*)aInput key:(NSString*)aKey{     NSMutableArray *iS = [[NSMutableArray alloc] initWithCapacity:256];    NSMutableArray *iK = [[NSMutableArray alloc] initWithCapacity:256];     for (int i= 0; i<256; i++) {        [iS addObject:[NSNumber numberWithInt:i]];    }     int j=1;     for (short i=0; i<256; i++) {         UniChar c = [aKey characterAtIndex:i%aKey.length];         [iK addObject:[NSNumber numberWithChar:c]];    }     j=0;     for (int i=0; i<255; i++) {        int is = [[iS objectAtIndex:i] intValue];        UniChar ik = (UniChar)[[iK objectAtIndex:i] charValue];         j = (j + is + ik)%256;        NSNumber *temp = [iS objectAtIndex:i];        [iS replaceObjectAtIndex:i withObject:[iS objectAtIndex:j]];        [iS replaceObjectAtIndex:j withObject:temp];     }     int i=0;    j=0;     NSString *result = aInput;     for (short x=0; x<[aInput length]; x++) {        i = (i+1)%256;         int is = [[iS objectAtIndex:i] intValue];        j = (j+is)%256;         int is_i = [[iS objectAtIndex:i] intValue];        int is_j = [[iS objectAtIndex:j] intValue];          int t = (is_i+is_j) % 256;        int iY = [[iS objectAtIndex:t] intValue];         UniChar ch = (UniChar)[aInput characterAtIndex:x];        UniChar ch_y = ch^iY;         result = [result stringByReplacingCharactersInRange:NSMakeRange(x, 1) withString:[NSString stringWithCharacters:&ch_y length:1]];    }     [iS release];    [iK release];     return result;}

　RC4算法的原理很简单，包括初始化算法（KSA）和伪随机子密码生成算法（PRGA)两大部分。假设S-box的长度为256，密钥长度为Len。先来看看算法的初始化部分（用C代码表示）：　　其中，参数1是一个256长度的char型数组，定义为: unsigned char sBox[256];　　参数2是密钥，其内容可以随便定义：char key[256];　　参数3是密钥的长度，Len = strlen(key);　　void rc4_init(unsigned char *s, unsigned char *key, unsigned long Len)　　{　　int i =0, j = 0, k[256] = {
    0};　　unsigned char tmp = 0;　　for(i=0;i<256;i++)　　{　　s[i]=i;　　k[i]=key[i%Len];　　}　　for (i=0; i<256; i++)　　{　　j=(j+s[i]+k[i])%256;　　tmp = s[i];　　s[i] = s[j]; //交换s[i]和s[j]　　s[j] = tmp;　　}　　}　　在初始化的过程中，密钥的主要功能是将S-box搅乱，i确保S-box的每个元素都得到处理，j保证S-box的搅乱是随机的。而不同的S-box在经过伪随机子密码生成算法的处理后可以得到不同的子密钥序列，将S-box和明文进行xor运算，得到密文，解密过程也完全相同。　　再来看看算法的加密部分（用C代码表示）：　　其中，参数1是上边rc4_init函数中，被搅乱的S-box;　　参数2是需要加密的数据data;　　参数3是data的长度.　　void rc4_crypt(unsigned char *s, unsigned char *Data, unsigned long Len)　　{　　int x = 0, y = 0, t = 0, i = 0;　　unsigned char tmp;　　for(i=0;i
      
       　　#include
       
        　　typedef unsigned long ULONG;　　void rc4_init(unsigned char *s, unsigned char *key, unsigned long Len) //初始化函数　　{　　int i =0, j = 0；　　char k[256] = {
    0};　　unsigned char tmp = 0;　　for(i=0;i<256;i++)　　{　　s[i]=i;　　k[i]=key[i%Len];　　}　　for (i=0; i<256; i++)　　{　　j=(j+s[i]+k[i])%256;　　tmp = s[i];　　s[i] = s[j]; //交换s[i]和s[j]　　s[j] = tmp;　　}　　}　　void rc4_crypt(unsigned char *s, unsigned char *Data, unsigned long Len) //加解密　　{　　int i = 0, j = 0, t = 0;　　unsigned long k = 0;　　unsigned char tmp;　　for(k=0;k