Cryptography and molecular biology share certain aspects and operations that allow for a set of unified principles to be applied to problems in either venue. A DNA-inspired hash code system is presented that utilizes concepts from molecular biology. It is a keyed-Hash Message Authentication Code (HMAC) capable of being used in secure mobile ad-hoc networks. It is targeted for applications without an available public key infrastructure. Ad-hoc does not mean the users are completely unknown to each other. They could be part of a military unit, police, emergency workers, mobile vendors, or any collection of users in a common geographical area that wish to communicate in a region lacking a PKI (Public Key Infrastructure).

Cryptography transforms messages between two states: plain and encrypted. Cryptography uses operations such as circular shifts, bit expansions, bit padding, and arithmetic operations to create ciphertext. These operations have analogs in molecular biology, e.g., transposable elements. Genes are capable of expressing a wide range of products, such as proteins based upon an alphabet of only four symbols. This research implements a keyed-HMAC system using a DNA-based code and certain principles from molecular biology. The system will permit Mobile Ad-hoc Networks (MANET) to distinguish trusted peers, yet tolerate the ingress and egress of nodes on an unscheduled, unpredictable basis.

There is an infinite number of DNA sequence combinations that cannot be brute-force searched within exponential time. The system will ultimately allow encryption at the genomic level of organisms. The system relies on complementarity of a portion of the hash code output at the receiver to hash code output from the sender. A traditional authentication system using hash codes requires equality of the sender and receiver hash codes. The hash code contains a cryptographic sequence that is calculated over a portion of the cleartext message and a check sum calculated over the entire ciphertext message; the check sums from sender and receiver must be equal.

An annealing function creates a one-way association in the ciphertext of the hash code output that cannot be reversed. The hash code is designed for implementation into actual DNA genomes.

This work was done by Harry Shaw of Goddard Space Flight Center and Sayed Hussein of George Washington University. GSC-16096-1

NASA Tech Briefs Magazine

This article first appeared in the December, 2014 issue of NASA Tech Briefs Magazine.

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