在iOS开发中，为了数据的安全经常对内容进行加密，在这儿我们对经常使用的加密算法进行了总结：

1、MD5

<span style="font-size:18px;">+ (NSString *)md5Hash:(NSString *)str {

    const char *cStr = [str UTF8String];

    unsigned char result[16];

    CC_MD5( cStr, strlen(cStr), result );

    NSString *md5Result = [NSString stringWithFormat:

                           @"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",

                           result[0], result[1], result[2], result[3],

                           result[4], result[5], result[6], result[7],

                           result[8], result[9], result[10], result[11],

                           result[12], result[13], result[14], result[15]

                           ];

    return md5Result;

}</span>

2. SHA1数字签名算法

<span style="font-size:18px;">const char *cstr = [str cStringUsingEncoding:NSUTF8StringEncoding];

    NSData *data = [NSData dataWithBytes:cstr length:str.length];

    uint8_t digest[CC_SHA1_DIGEST_LENGTH];

    CC_SHA1(data.bytes, data.length, digest);

    NSMutableString* output = [NSMutableString stringWithCapacity:CC_SHA1_DIGEST_LENGTH * 2];

    for(int i = 0; i < CC_SHA1_DIGEST_LENGTH; i++) {

        [output appendFormat:@"%02x", digest[i]];

    }

    return output;

</span>

3.AES加密算法

<span style="font-size:18px;">- (NSData *)AES256EncryptWithKey:(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 *)AES256DecryptWithKey:(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;

}

</span>

4、BASE64编码

<span style="font-size:18px;">+ (NSString*)encodeBase64String:(NSString * )input {

    NSData *data = [input dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES];

    data = [GTMBase64 encodeData:data];

    NSString *base64String = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease];

	return base64String;

}

+ (NSString*)decodeBase64String:(NSString * )input {

    NSData *data = [input dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES];

    data = [GTMBase64 decodeData:data];

    NSString *base64String = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease];

	return base64String;

} 

+ (NSString*)encodeBase64Data:(NSData *)data {

	data = [GTMBase64 encodeData:data];

    NSString *base64String = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease];

	return base64String;

}

+ (NSString*)decodeBase64Data:(NSData *)data {

	data = [GTMBase64 decodeData:data];

    NSString *base64String = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease];

	return base64String;

}</span>