iOS NSData 常用 Category（类目）分享

1、NSData的MD5加密

#define CC_MD5_DIGEST_LENGTH    16
//计算NSData 的MD5值
+ (NSString*)getMD5WithData:(NSData *)data{
    //需要MD5变量并且初始化
    CC_MD5_CTX  md5;
    CC_MD5_Init(&md5);
    //开始加密(第一个参数：对md5变量去地址，要为该变量指向的内存空间计算好数据，第二个参数：需要计算的源数据，第三个参数：源数据的长度)
    CC_MD5_Update(&md5, data.bytes, (CC_LONG)data.length);
    //声明一个无符号的字符数组，用来盛放转换好的数据
    unsigned char result[CC_MD5_DIGEST_LENGTH];
    //将数据放入result数组
    CC_MD5_Final(result, &md5);
    //将result中的字符拼接为OC语言中的字符串，以便我们使用。
    NSMutableString *resultString = [NSMutableString string];
    for (int i = 0; i < CC_MD5_DIGEST_LENGTH; i++) {
        [resultString appendFormat:@"%02X",result[i]];
    }
    return  resultString;
}

2、NSData的AES256加密、解密

- (NSData *)aes256_encrypt:(NSString *)key   //加密
{
    char keyPtr[kCCKeySizeAES256+1];
    bzero(keyPtr, sizeof(keyPtr));
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    NSUInteger dataLength = [self length];
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    size_t numBytesEncrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128,
                                          kCCOptionPKCS7Padding | kCCOptionECBMode,
                                          keyPtr, kCCBlockSizeAES128,
                                          NULL,
                                          [self bytes], dataLength,
                                          buffer, bufferSize,
                                          &numBytesEncrypted);
    if (cryptStatus == kCCSuccess) {
        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
    }
    free(buffer);
    return nil;
}


- (NSData *)aes256_decrypt:(NSString *)key   //解密
{
    char keyPtr[kCCKeySizeAES256+1];
    bzero(keyPtr, sizeof(keyPtr));
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    NSUInteger dataLength = [self length];
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    size_t numBytesDecrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128,
                                          kCCOptionPKCS7Padding | kCCOptionECBMode,
                                          keyPtr, kCCBlockSizeAES128,
                                          NULL,
                                          [self bytes], dataLength,
                                          buffer, bufferSize,
                                          &numBytesDecrypted);
    if (cryptStatus == kCCSuccess) {
        return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
        
    }
    free(buffer);
    return nil;
}