# Tag Info

## Hot answers tagged differential-analysis

13

Basically it's analysis of a cryptographic cypher by the means of finding a relationship between the difference in the input data and the output data. Ideally, the slightest difference in input data (cleartext), even a single bit, should produce a completely different cypthertext. However, if the cypher is not well-designed, a correlation between the two ...

7

Differential cryptanalysis works on differences. Linear cryptanalysis works on linearity. Neat, isn't it ? Instead of speaking of how they differ, it is easier to list their common features. Both kinds of attacks: Use a lot of known pairs plaintext/ciphertext (many input messages encrypted with the same key, and, for each of them, the attacker knows both ...

5

No, it's not flawed. You're just running into a fact of life; differential cryptanalysis generally doesn't just give you the entire key (or even subkey) in one shot. It generally gives you partial information about the key, and if you want the entire key, well, you need to work at it more. In this phase of the attack, you know that the last round subkey ...

4

There are 256! possible 8x8 S-boxes (i.e., bijective functions from $\{0,1\}^8$ to $\{0,1\}^8$. This is an absolutely enormous number. You couldn't possibly enumerate all of them within the lifetime of the universe. So, yes, this is one reason why it is not straightforward to determine whether there exists such a S-box with differential uniformity 2. ...

3

This is called an Even-Mansour cipher. Actually, for the differential cryptanalysis it does not matter what sort of difference you use, you only need that it propagates deterministically through linear transformations (whatever linearity means). In this case you use a difference modulo $2^{32}$: $$A \boxminus B \equiv (A-B)\pmod{2^{32}}.$$ You compute ...

3

The design documents for Rijndael explain exactly how the designers proved its resistance to differential cryptanalysis. Read their submission to the AES competition process, particularly Section 8.2 and the Annex. To understand their approach, it will probably help to understand differential cryptanalysis and read some of the related literature. You can ...

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