NSData+Hash.m

#import "NSData+Hash.h"
#import <CommonCrypto/CommonDigest.h>

@implementation NSData (Hash)

- (NSData *)SHA1
{
    unsigned char hash[CC_SHA1_DIGEST_LENGTH];
    if (CC_SHA1([self bytes], [self length], hash))
    {
        return [NSData dataWithBytes:hash
                              length:CC_SHA1_DIGEST_LENGTH];
    }
    return nil;
}

- (NSString *)SHA1String
{
    NSMutableString *output = [NSMutableString stringWithCapacity:CC_SHA1_DIGEST_LENGTH];
    NSData *SHA1 = [self SHA1];
    if (SHA1.length == CC_SHA1_DIGEST_LENGTH)
    {
        uint8_t digest[CC_SHA1_DIGEST_LENGTH];
        [SHA1 getBytes:&digest length:CC_SHA1_DIGEST_LENGTH];
        for (int index = 0; index < CC_SHA1_DIGEST_LENGTH; index++)
        {
            [output appendFormat:@"%02x", digest[index]];
        }
        return output;
    }
    return nil;
}

@end