中文的异或加密有一个很诡异的现象，就是可能会secretKey的值不一样而导致异或后得到的数据为nil，所以在异或加密之前，我们需要将所要加密的字符串转义。代码如下

/**
 异或加密
 
 @param plainText 要加密的字符串
 @param secretKey 秘钥
 @return 加密后返回的字符传
 */
- (NSString *)stringXOREncryptWithPlainText:(NSString *)plainText secretKey:(NSString *)secretKey {
    
    NSData *codeKeyData =  [secretKey dataUsingEncoding:NSUTF8StringEncoding];
    Byte codeKeyByteAry[codeKeyData.length];
    for (int i = 0 ; i < codeKeyData.length; i++) {
        NSData *idata = [codeKeyData subdataWithRange:NSMakeRange(i, 1)];
        codeKeyByteAry[i] =((Byte*)[idata bytes])[0];
    }
    
    NSMutableData *returnData = [[NSMutableData alloc] init];
    
    NSString *charactersToEscape = @"?!@#$^&%*+,:;='\"`<>()[]{}/\\| ";
    NSCharacterSet *allowedCharacters = [[NSCharacterSet characterSetWithCharactersInString:charactersToEscape] invertedSet];
    // 对需要加密的数据进行转义
    plainText = [plainText stringByAddingPercentEncodingWithAllowedCharacters:allowedCharacters];
    NSData *strData =  [plainText dataUsingEncoding:NSUTF8StringEncoding];
    for (int i = 0 ; i < strData.length; i++) {
        NSData *idata = [strData subdataWithRange:NSMakeRange(i, 1)];
        Byte byte =((Byte*)[idata bytes])[0];
        Byte byte2 = codeKeyByteAry[i%codeKeyData.length];
        Byte returnbyte = byte^byte2;
        Byte returnbyteAry[1];
        returnbyteAry[0] = returnbyte;
        [returnData appendBytes:returnbyteAry length:1];
    }
    NSString *returnStr =  [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];
    return returnStr;
}

当然，在解密的时候要移除转义

/**
 异或解密
 */
- (NSString *)stringXORDeocodeWithPlainText:(NSString *)plaintext secretKey:(NSString *)secretKey {
    
    NSData *codeKeyData =  [secretKey dataUsingEncoding:NSUTF8StringEncoding];
    Byte codeKeyByteAry[codeKeyData.length];
    for (int i = 0 ; i < codeKeyData.length; i++) {
        NSData *idata = [codeKeyData subdataWithRange:NSMakeRange(i, 1)];
        codeKeyByteAry[i] =((Byte*)[idata bytes])[0];
    }
    
    NSData *strData =  [plaintext dataUsingEncoding:NSUTF8StringEncoding];
    
    NSMutableData *returnData = [[NSMutableData alloc] init];
    for (int i = 0 ; i < strData.length; i++) {
        NSData *idata = [strData subdataWithRange:NSMakeRange(i, 1)];
        Byte byte =((Byte*)[idata bytes])[0];
        Byte byte2 = codeKeyByteAry[i%codeKeyData.length];
        Byte returnbyte = byte^byte2;
        Byte returnbyteAry[1];
        returnbyteAry[0] = returnbyte;
        [returnData appendBytes:returnbyteAry length:1];
    }
    NSString *returnStr =  [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];
    // 要移除转义
    returnStr = [returnStr stringByRemovingPercentEncoding];
    return returnStr;
}

运行测试结果如下

    NSString *input = @"这里是中文异或";
    NSString *codeKey = @"secretkey";
    NSString *encodeString = [self stringXOREncryptWithPlainText:input secretKey:codeKey];
    NSString *decodeString = [self stringXORDeocodeWithPlainText:encodeString secretKey:codeKey];
    NSLog(@"加密前：%@",input);
    NSLog(@"加密后：%@",encodeString);
    NSLog(@"解密后：%@",decodeString);

1546605145262.jpg

OK!