Abstract: A system and method to general cryptographically secure digital signatures using universal composition is disclosed herein. An example system includes a first secure device that generates a first private key according to a first cryptographic scheme, and in response to receiving document data, generates a first signature according to the first cryptographic scheme using the document data and the first private key. The example system also includes a second secure device that generates a second private key according to a second cryptographic scheme, generates a second signature according to the second cryptographic scheme using composite data and the second private key, generates a total signature based on the first signature, the second signature, and the supplemental data, and appends the total signature to a digital document from which the document data was derived.