US Patent 8006299 Encryption and authentication systems and methods

Methods, apparatus, and systems are disclosed for, among other things, passphrase input using secure delay, passphrase input with characteristic shape display, user authentication with non-repeated selection of elements with a displayed set of elements, document authentication with embedding of a digital signature stamp within a graphical representation of the electronic document wherein the stamp comprises digits of a digital signature, and sub-hash computation using secure delay.