Creating UUID and UDID in iOS 7

Question

I want to create UUID, I have code below which can create UUID, how can I create UDID with multiple vendors same ID in iOS7?

+ (NSString*) stringWithNewUUID
{
    CFUUIDRef uuidObj = CFUUIDCreate(nil);
    NSString *newUUID = (NSString*)CFUUIDCreateString(nil, uuidObj);
    CFRelease(uuidObj);
    return newUUID;
}

Answer 1

I have created a vendor ID and then saved it with keychain, which I am retaining for next time using KeychainWrapper keychainStringFromMatchingIdentifier:...