What is the block size and key size of the SHARK cipher?
The SHARK cipher operated with a 64-bit block size and a 128-bit key size. This configuration created a six-round SP-network that alternated between key mixing and transformation layers.
Questions about Shark
Short answers, pulled from the story.
How did the SHARK cipher achieve data diffusion?
The SHARK cipher utilized an MDS matrix derived from a Reed, Solomon error correcting code to guarantee excellent diffusion of data across the cipher. This linear transformation ensured that a change in a single bit of the input would ripple through the entire output block.
When was a vulnerability discovered in the SHARK cipher?
A specific vulnerability emerged in the late 1990s when researchers Jakobson and Knudsen demonstrated that five rounds of a modified version of SHARK could be broken in 1997. This attack used an interpolation method to reconstruct the secret key by analyzing the relationship between the input and output of the S-boxes.
How did the SHARK cipher influence the Advanced Encryption Standard?
The SHARK cipher laid the mathematical groundwork for Rijndael, the algorithm that eventually won the competition to become the Advanced Encryption Standard. Designers Joan Daemen and Vincent Rijmen drew heavily from the structural concepts established by SHARK, including the use of MDS matrices and the specific configuration of S-boxes.
What mathematical function did the SHARK cipher use for its S-boxes?
The nonlinear layer of the SHARK cipher relied on eight 8×8-bit S-boxes constructed from the function F(x) equals x to the power of negative one over the Galois Field GF(2 to the 8th power). This specific mathematical operation provided a high degree of nonlinearity to make it difficult for cryptanalysts to establish linear relationships between the plaintext and the ciphertext.