Example code for calculating a UUID 5 on iOS. It does not give correct results. EXPECTED: b31c0937-b03b-5a5e-b47a-b80881530929 ACTUAL: 59F5ADDE-9E13-578E-BB37-C3200E80A1B9

NSUUID+DLExtensions.mm

#import "NSUUID+DLExtensions.h"
#import <CommonCrypto/CommonDigest.h>

@implementation NSUUID (DLExtensions)

+ (NSUUID*)withNamespaceUUID:(NSUUID*)namespace name:(NSString*)name
{
    NSString *concatenatedName = [[namespace UUIDString] stringByAppendingString:name];

    NSData *data = [concatenatedName dataUsingEncoding:NSUTF8StringEncoding];
    uint8_t digest[CC_SHA1_DIGEST_LENGTH];
    uuid_t bytes;

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

    // TEMPORARY--Just log the new UUID
    NSMutableString *dontUse = [NSMutableString stringWithCapacity:CC_SHA1_DIGEST_LENGTH];

    for (int i = 0; i < CC_SHA1_DIGEST_LENGTH; i++) {
        [dontUse appendFormat:@"%02x", digest[i]];
    }

    NSLog(@"CRYPTO'D STRING = %@", dontUse);
    // END TEMPORARY
    
    // Fill in the UUID bytes, masking in the version and reserved bits
    bytes[0]  = digest[0];   // time_low
    bytes[1]  = digest[1];
    bytes[2]  = digest[2];
    bytes[3]  = digest[3];
    bytes[4]  = digest[4];   // time_mid
    bytes[5]  = digest[5];
    bytes[6]  = ((digest[6] & 0x0F) | 0x50); // time_hi_and_version
    bytes[7]  = digest[7];
    bytes[8]  = ((digest[8] & 0x3F) | 0xB0); // clock_seq_hi_and_reserved
    bytes[9]  = digest[9];  // clock_seq_low
    bytes[10] = digest[10]; // node
    bytes[11] = digest[11];
    bytes[12] = digest[12];
    bytes[13] = digest[13];
    bytes[14] = digest[14];
    bytes[15] = digest[15];

    // TEMPORARY
    NSLog(@"Computed UUID: %@", [[[[NSUUID alloc] initWithUUIDBytes:bytes] autorelease] UUIDString]);
    // END TEMPORARY
    
    return [[[NSUUID alloc] initWithUUIDBytes:bytes] autorelease];
}

@end

BTW, you can, and I recommend it, make these private. Anybody with the link can still read them.

Is it possible to change this one?

Say guys, did you ever figure out a workable objective C implementation of UUID5 (or UUID3)? I see this was attempted some time ago (not sure if it was intended to be public from the comments there). Just curious before I attempt implementing RFC 4122 if you guys found a way beyond this.

Never mind, implementation wasn't hard, got it working.

Just in case anyone needs uuid5 calculation in url namespace https://gist.github.com/superduper/177aab4b9700e41103e3

I had problems with both Rob and Victor's implementations because I needed to interoperate with (and match) uuid5 strings generated by a python backend. Using their code as a starting point I've created a drop-in NSUUID category that works correctly. It's MIT licensed so you are free to do with it as you like.
https://gist.github.com/eliburke/1a55ed616bb15a7f908b

If you prefer to fix Rob's code, you need to use the raw bytes from the namespace UUID and change his clock_seq_hi_and_reserved line to use 0x80 instead of 0xB0.

If you prefer to fix Victor's code, change his calculation of bytes[8] from
bytes[8] = ((bytes[8] | 0x40) & 0x7F); // bad code, sets bits to 0100 xxxx
bytes[8] = ((bytes[8] & 0x3F) | 0x80); // good code, sets bits to 10xx xxxx