Vortrag von Josua Rutishauser
Datum: 28.09.22 Zeit: 15.00 - 16.00 Raum: Y27H25
Digital signatures are used to confirm the legitimate sender of a message or key of a symmetric cryptosystem. The receiver of a message (or key) is able to verify with a public shared key if the signature, and thus the message has been sent from the person that it claims to be from. To do so one uses asymmetric cryptosystems, and therefore trapdoor one-way functions.
In my master thesis two connected signature schemes are introduced: The unbalanced) Oil & Vinegar and Rainbow signature scheme; both of which use multivariate quadratic polynomials to produce signatures. The (unbalanced) Oil & Vinegar scheme uses a trapdoor which allows the signer to solve a linear set of multivariate equations, while a forger trying to attack the system needs to solve a set of multivariate quadratic equations. For well chosen parameters, the forgers task is way harder. The Rainbow signature scheme is based on (unbalanced) Oil & Vinegar and uses multiple layers of this scheme to make it more complex and more efficient. This talk will give a brief overview at different approaches to attack the signature schemes and explains which parameters are the most effective dependant on the attacks. Moreover, we’ll see that implementation wise, both signature schemes can be kept short in the programmin language python and compare the computation times of both algorithms while discussing other aspects of security in foresight of Rainbow being a third-round finalist at NIST for the standardizising process in post-quantum cryptography.
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