Cryptology and Security of Protocols

Researchers

Rogério Reis, António Machiavelo ( CMUP), Bruno Ribeiro, João Mendes, Bruno Caxeira, José Borges, Alexandra Queirós, Ivone Amorim,

Cryptanalysis of classical symmetric ciphers
A full automated cipher-text-only cryptanalysis attack on the Bifid cipher was developed and implemented. This work was reported in [1]. We also analysed and studied the plausibility of the polish cryptanalysis attacks of the Enigma (1932-1939) described in the literature.

Ongoing and future work: An algebraic characterization of the Enigma machine as well as some generalization of these kind of cyphers. Study of the fundamental weaknesses of this family of cyphers and possible alternatives to difficult its attacks even for an opponent with access to an actual time computer [2].

[1] A. Machiavelo and R. Reis, Automated ciphertext-only cryptanalysis of the Bifid cipher, Cryptologia, 31,2, 112-124, 2007.

[2] B. Ribeiro, The Enigma cryptanalysis: 1932-1939. MSc in Mathematical Engineering, FCUP.2007
Formal analysis of the security features of cryptographic protocols
We aim to study security proprieties of modern protocols using symmetric and public-key cryptography.

Ongoing and future work: A network simulator was developed for the analysis of the security properties of peer-to-peer protocols. We plan to analyse their security promises, produce proofs of their weakness and programs that can exploit these vulnerabilities, and construct tentative solutions to fix them.
We also working in the following topics:

A python module that implements Elliptic Curve arithmetics and thus permits easy implementations of Elliptic Curve Cryptography algorithms.
An implementation of Pomerance quadratic sieve integer factoring algorithm.
An implementation of a secure electronic voting system using Pallier's Public Key Cryptosystem.
Development of an open source public key infrastructure (PKI) that can scale to a realistic dimension and that uses the concept of measure of trust for each public key stored.