iOS AES/Des解密 偏移量取加密数据的前16位(Byte

最近在弄AES解密,解密方法是 iv取加密文件内容的前16位,然后解密之后把内容里面的填充字符b"\0"去掉

1.首先是把data转成Byte数组 然后取前16位

Byte *testByte = (Byte *)[data bytes];
Byte *bytes =malloc(sizeof(*bytes)*data.length);
for(int i=0;i<16;i++){
    bytes[i] = testByte[i];
}

2.跟后端同步好补位方法 我这里是不补位填0 其他补位方法自行查找

3.去掉数据里面补位的0,我这里是把data转换成字符串 ,我这边是不足16位,会补够0到16位

+(NSString *)AES128Decrypt:(NSData *)data key:(NSString *)key{
    char keyPtr[kCCKeySizeAES128 + 1];
    memset(keyPtr, 0, sizeof(keyPtr));
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];

    NSUInteger dataLength = [data length];
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    
    //16字节的偏移量
    Byte *testByte = (Byte *)[data bytes];
    Byte *bytes =malloc(sizeof(*bytes)*data.length);
    for(int i=0;i<16;i++){
        bytes[i] = testByte[i];
    }
    size_t numBytesCrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
                                          kCCAlgorithmAES128,
                                          0,//不补位
                                          keyPtr,
                                          kCCBlockSizeAES128,
                                          bytes,
                                          [data bytes],
                                          dataLength,
                                          buffer,
                                          bufferSize, &numBytesCrypted);
    if (cryptStatus == kCCSuccess) {
        //原始数据
        NSData *resultData = [NSData dataWithBytesNoCopy:buffer length:numBytesCrypted];
        //原始数据去掉前面16位的偏移量
        NSData *subData = [resultData subdataWithRange:NSMakeRange(16, resultData.length-16)];
        //方法:https://www.jianshu.com/p/fb9d3a69d3d3
        NSString *plaintext = @"";
        char termChar[1] = {'\0'};
        NSMutableData *data = [NSMutableData dataWithBytes:subData.bytes length:subData.length];
        [data appendBytes:termChar length:1];
        plaintext = [[NSString alloc] initWithCString:data.bytes encoding:NSUTF8StringEncoding];
        return plaintext;
    }
    free(buffer);
    return nil;
}

AES解密使用方法

    NSData *testData = [NSData dataWithContentsOfFile:[[NSBundle mainBundle]pathForResource:@"1.txt" ofType:@""]];
    NSString *laststr = [QLAESDecrypt AES128Decrypt:testData key:@"keykeykey"];
    NSLog(@"laststr::%@",laststr);

下面是Des解密 单纯MARK下

//Des解密
+(NSData *)decryptUseDES:(NSString *)plainText key:(NSString *)key{

    NSData *plaindata = nil;
    NSData *cipherdata = [[NSData alloc] initWithBase64EncodedString:plainText options:NSDataBase64DecodingIgnoreUnknownCharacters];
    
    size_t bufferSize = cipherdata.length;
    void * buffer = malloc(bufferSize);

    NSData * date = [key dataUsingEncoding:NSUTF8StringEncoding];
    size_t numBytesDecrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
                                          kCCAlgorithmDES,/* 算法 */
                                          kCCOptionPKCS7Padding,
                                          [key UTF8String],
                                          kCCKeySizeDES,
                                          [date bytes],
                                          [cipherdata bytes],
                                          [cipherdata length],
                                          buffer,
                                          bufferSize,
                                          &numBytesDecrypted);
    if(cryptStatus == kCCSuccess)
    {
        plaindata = [NSData dataWithBytes:buffer length:(NSUInteger)numBytesDecrypted];
        return plaindata;
        
    }
    
     return plaindata;
}