Systems and methods for detecting copies of documents are described. In one example, a system and method for detecting copies of documents utilizes multiple correlations of original and scanned copy detection patterns. The system captures a CDP that may be skewed or improperly sized. The system also retrieves or reconstitutes the expected CDP. In order to provide a more reliable comparison and without manipulating the captured CDP, the system manipulates the orientation or rotation and resolution or size of the retrieved or reconstituted CDP to register it with the captured CDP. Then the system performs a first correlation to determine if the captured CDP indicates the correct document identification and then if necessary, a second correlation to determine authentication such as by performing a 1 pixel shift multiple autocorrelation comparison of the two CDPs.