使用iOS进行Rc4加密解密

搜了一次，网络上绝大部分，都转的是下面的这个封装的：

http://www.cocoachina.com/bbs/read.php?tid-77608.html

首先非常感谢楼主的分享，但是使用后发现这个里面的代码实际上是有问题的：

为了帮后人摆脱此坑的困扰，本人稍微做了一下修正，具体如下：

+(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;
　 //改动1，s-box的长度应当是256，楼主之前写的是255
    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<256; 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;

    

    Byte byteBuffer[aInput.length];

    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];

        //改动2:增加交换is_i和is_j的具体内容

        [iS exchangeObjectAtIndex:i withObjectAtIndex:j];

        UniChar ch = (UniChar)[aInput characterAtIndex:x];
        UniChar ch_y = ch^iY;

        

        byteBuffer[x] = ch_y;

    }

    [iS release];
    [iK release];

    return result;
}

+ (NSString *)byteToBase64String:(Byte [])byteBuffer lengh:(NSInteger)buffLen

{

    NSData *adata = [[NSData alloc] initWithBytes:byteBuffer length:buffLen];

    NSString *string = [adata base64EncodedStringWithOptions:0];

    return string;

}

参考资料：

http://baike.baidu.com/link?url=GDR7_BqVSKStCioLhfGikGMJ_MBwiGCsuB1bowM3ZRvZ0tNGesVt15AKLPXVjV5qfCaAMxwjolEM9dNy9ca3qa

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