iOS 超大文件MD5加密，超大文件hmac加密

1、在文件超过1G的时候，不能一次性放入内存之中，但是我们还是需要将这个文件进行md5加密，或者hmac系列的加密

这个时候我们需要用到一个系统的api——update系列的方法

注意：参数path为大文件所在的路径。

//MARK:大文件的MD5加密
+(NSString*)fileMD5:(NSString*)path
{
    NSFileHandle *handle = [NSFileHandle fileHandleForReadingAtPath:path];
    if( handle== nil ) return @"ERROR GETTING FILE MD5"; // file didnt exist

    CC_MD5_CTX md5;

    CC_MD5_Init(&md5);

    BOOL done = NO;
    while(!done)
    {
        NSData* fileData = [handle readDataOfLength:256];
        //        CHUNK_SIZE
        CC_MD5_Update(&md5, [fileData bytes], [fileData length]);
        if( [fileData length] == 0 ) done = YES;
    }
    unsigned char digest[CC_MD5_DIGEST_LENGTH];
    CC_MD5_Final(digest, &md5);
    NSString* s = [NSString stringWithFormat: @"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
                   digest[0], digest[1],
                   digest[2], digest[3],
                   digest[4], digest[5],
                   digest[6], digest[7],
                   digest[8], digest[9],
                   digest[10], digest[11],
                   digest[12], digest[13],
                   digest[14], digest[15]];
    return s;
}

//MARK:大文件的hmacSHA256加密
+ (NSString *)hmac:(NSString *)path withKey:(NSString *)key
{
    NSFileHandle *handle = [NSFileHandle fileHandleForReadingAtPath:path];

    if( handle== nil ) return @"ERROR GETTING FILE hmac"; // file didnt exist

    CCHmacContext ctx;

    const char *cKey  = [key cStringUsingEncoding:NSASCIIStringEncoding];

    unsigned char cHMAC[CC_SHA256_DIGEST_LENGTH];

    CCHmacInit(&ctx, kCCHmacAlgSHA256, cKey, strlen(cKey));

    BOOL done = NO;
    while(!done)
    {
        NSData* fileData = [handle readDataOfLength:256];

        CCHmacUpdate(&ctx, [fileData bytes], [fileData length]);

        if( [fileData length] == 0 ) done = YES;
    }

    CCHmacFinal(&ctx, cHMAC);

    NSData *HMACData = [NSData dataWithBytes:cHMAC length:sizeof(cHMAC)];

    const unsigned char *buffer = (const unsigned char *)[HMACData bytes];

    NSMutableString *HMAC = [NSMutableString stringWithCapacity:HMACData.length * 2];

    for (int i = 0; i < HMACData.length; ++i){
        [HMAC appendFormat:@"%02x", buffer[i]];
    }

    return HMAC;
}

原文地址：https://www.cnblogs.com/yyyyyyyyqs/p/11451618.html