Best way to serialize an NSData into a hexadeximal string

I am looking for a nice-cocoa way to serialize an NSData object into a hexadecimal string. The idea is to serialize the deviceToken used for notification before sending it to my server.

I have the following implementation, but I am thinking there must be some shorter and nicer way to do it.

+ (NSString*) serializeDeviceToken:(NSData*) deviceToken
{
    NSMutableString *str = [NSMutableString stringWithCapacity:64];
    int length = [deviceToken length];
    char *bytes = malloc(sizeof(char) * length);

    [deviceToken getBytes:bytes length:length];

    for (int i = 0; i < length; i++)
    {
        [str appendFormat:@"%02.2hhX", bytes[i]];
    }
    free(bytes);

    return str;
}