1 research outputs found
Algebraic Attack Efficiency versus S-box Representation
Algebraic analysis of block ciphers aims at finding the secret key by solving
a collection of polynomial equations that describe the internal structure of a cipher
for chosen observations of plaintext/ciphertext pairs.
Although algebraic attacks are addressed for cryptanalysis of block and
stream ciphers, there is a lack of understanding of the impact of algebraic
representation of the cipher on efficiency of solving the resulting collection of equations.
The work investigates different S-box representations and their effect on
complexity of algebraic attacks.
In particular, we observe that a S-box representation defined in the work as
\textit{Forward-Backward} (FWBW) leads to a collection of equations that can be solved efficiently.
We show that the cipher can be broken using
standard algebra software \textsc{Singular} and FGb.
This is the best result achieved so far.
The effect of description of S-boxes for some light-weight block ciphers is investigated.
A by-product of this result is that we have achieved some improvements on the algebraic cryptanalysis of LBlock, PRESENT and MIBS light-weight block ciphers.
Our study and experiments confirms a counter-intuitive conclusion
that algebraic attacks work best for the FWBW S-box representation.
This contradicts a common belief that algebraic attacks are more efficient
for quadratic S-box representation