NSData to Hex String

Hello!

I have a SecKeyRef () from generating a private/public key pair with the CryptoExercise from Apple (CryptoExercise).

This is a NSData which I will transform to a hex string.
I found these two implementations:

@interface NSData (NSData_HexAdditions)
- (NSString*) stringWithHexBytes1;
- (NSString*) stringWithHexBytes2;
@end

@implementation NSData (NSData_HexAdditions)
- (NSString*) stringWithHexBytes {
	NSMutableString *stringBuffer = [NSMutableString stringWithCapacity:([self length] * 2)];
	const unsigned char *dataBuffer = [self bytes];
	int i;
	for (i = 0; i < [self length]; ++i) {
		[stringBuffer appendFormat:@"%02X", (unsigned long)dataBuffer[i]];
	}
	return [[stringBuffer copy] autorelease];
}

- (NSString*)stringWithHexBytesss {
	static const char hexdigits[] = "0123456789ABCDEF";
	const size_t numBytes = [self length];
	const unsigned char* bytes = [self bytes];
	char *strbuf = (char *)malloc(numBytes * 2 + 1);
	char *hex = strbuf;
	NSString *hexBytes = nil;

	for (int i = 0; i<numBytes; ++i) {
		const unsigned char c = *bytes++;
		*hex++ = hexdigits[(c >> 4) & 0xF];
		*hex++ = hexdigits[(c ) & 0xF];
	}
	*hex = 0;
	hexBytes = [NSString stringWithUTF8String:strbuf];
	free(strbuf);
	return hexBytes;
}
@end

And I use it so:

[publicKey stringWithHexBytes1]
[publicKey stringWithHexBytes2]

Both results are the same, but which one is faster and should I use?

And: I put the above source code in my ABCController.m. I think it is not a good idea to do that. Should I create a NSData.h and NSData.m class for that code or what's the best solution?

Thanks & Regards.