Creating SHA1 Hash from NSString

I quite like hypercrypt's answer, but I've been encouraged to post my comment.

You could look at CC_SHA1, or this related SO question.

- (NSString *)sha1:(NSString *)str {
const char *cStr = [str UTF8String];
unsigned char result[CC_SHA1_DIGEST_LENGTH];
CC_SHA1(cStr, strlen(cStr), result);
NSString *s = [NSString  stringWithFormat:
           @"%02x%02x%02x%02x%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],
           result[16], result[17], result[18], result[19]
           ];

return s;
}

I have this in a category on NSString (available at https://github.com/hypercrypt/NSString-Hashes):

#import <CommonCrypto/CommonDigest.h>

...

- (NSString *)sha1
{
    NSData *data = [self dataUsingEncoding:NSUTF8StringEncoding];
    uint8_t digest[CC_SHA1_DIGEST_LENGTH];

    CC_SHA1(data.bytes, (CC_LONG)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;
}

Starting with Xcode 10.0, you should use import CommonCrypto instead since it is now natively available in Swift! If you have recently migrated to Xcode 10.0 and use the old approach, this can be your cue to make the change:

Command CompileSwift failed with a nonzero exit code

It took me a while to port @hypercrypt solution to Swift so I decided to share it with others that might have the same problem.

One important thing to note is that you need CommonCrypto library, but that library does not have Swift module. The easiest workaround is to import it in your bridging header:

#import <CommonCrypto/CommonCrypto.h>

Once imported there, you do not need anything else. Just use String extension provided:

extension String
{
    func sha1() -> String
    {
        var selfAsSha1 = ""

        if let data = self.dataUsingEncoding(NSUTF8StringEncoding)
        {
            var digest = [UInt8](count: Int(CC_SHA1_DIGEST_LENGTH), repeatedValue: 0)
            CC_SHA1(data.bytes, CC_LONG(data.length), &digest)

            for index in 0..<CC_SHA1_DIGEST_LENGTH
            {
                selfAsSha1 += String(format: "%02x", digest[Int(index)])
            }
        }

        return selfAsSha1
    }
}

Notice that my solution does not take effect of reserving capacity what NSMutableString has in original post. However I doubt anyone will see the difference :)