Differential Cryptanalysis
Differential cryptanalysis, introduced by Biham and Shamir, exploits the differential propagation properties of S-boxes to trace how input differences propagate through the rounds and recover the key.
Purpose
It evaluates a block cipher’s resistance to differential propagation and is the main driver behind S-box differential uniformity and round-count design.
Mechanism
A high-probability differential characteristic is built across rounds to predict the output difference for a given input difference; large numbers of chosen-plaintext pairs verify it and recover round keys. The AES S-box caps the maximum differential probability at 2^-6, limiting differential characteristics.
Use cases
- Differential attack assessment of DES
- Differential design of the AES S-box
- Block-cipher security analysis