Polynomial-time solutions of computational problems in noncommutative-algebraic cryptography
This work addresses a critical problem for cryptographers and security practitioners by breaking widely used protocols in noncommutative-algebraic cryptography, representing a significant rather than incremental advancement.
The paper tackles the security of key exchange protocols in noncommutative-algebraic cryptography by introducing the linear centralizer method, which provides a provable polynomial-time solution to break the Commutator and Centralizer key exchange protocols, marking the first such cryptanalysis for these protocols.
We introduce the \emph{linear centralizer method}, and use it to devise a provable polynomial time solution of the Commutator Key Exchange Problem, the computational problem on which, in the passive adversary model, the security of the Anshel--Anshel--Goldfeld 1999 \emph{Commutator} key exchange protocol is based. We also apply this method to the computational problem underlying the \emph{Centralizer} key exchange protocol, introduced by Shpilrain and Ushakov in 2006. This is the first provable polynomial time cryptanalysis of the Commutator key exchange protocol, hitherto the most important key exchange protocol in the realm of noncommutative-algebraic cryptography, and the first cryptanalysis (of any kind) of the Centralizer key exchange protocol. Unlike earlier cryptanalyses of the Commutator key exchange protocol, our cryptanalyses cannot be foiled by changing the distributions used in the protocol.