High security tagging system for evidence marking and verification

Optically encoded tags can provide highly secure, inexpensive assistance in verifying the identity and integrity of items including documents, containers, and parcels. An optically encoded tag system comprises means for producing the tag, means for affixing the tag, means for archiving the tag for future comparison, security provisions to restrict access to the archives, means for verifying the tag at a future time, security provisions to prevent duplication or removal and reapplication of the tags, management of distribution of overlays to authorized parties, and procedures to be followed when verification is successful and when it is not. Scenarios for its use in verification tagging applications, and mechanisms for production of the tags and overlays are described. The techniques developed are highly robust, in that they allow the pattern to be segmented and allow for dirt and other masking effects as well as partial defacement without loss of identity. They may be verified from unknown distances, and the verification process itself will provide distance information to facilitate lock-on for targeting purposes. Proof of principle has been demonstrated