Information security. 5. Information security based on secret key ciphers. Standardization and FEAL ciphers.

Security Analysis of Key-Alternating Feistel Ciphers

We study the security of key-alternating Feistel ciphers, a class of key-alternating ciphers with a Feistel structure. Alternatively, this may be viewed as the study of Feistel ciphers where the pseudorandom round functions are of the form Fi(x⊕ ki), where ki is the (secret) round key and Fi is a public random function that the adversary is allowed to query in a black-box way. Interestingly, ou...

Tight Security Bounds for Key-Alternating Ciphers

A t-round key-alternating cipher (also called iterated Even-Mansour cipher) can be viewed as an abstraction of AES. It defines a cipher E from t fixed public permutations P1, . . . , Pt : {0, 1} → {0, 1} and a key k = k0‖ · · · ‖kt ∈ {0, 1} by setting Ek(x) = kt⊕Pt(kt−1⊕Pt−1(· · · k1⊕P1(k0⊕ x) · · · )). The indistinguishability of Ek from a truly random permutation by an adversary who also has ...

On the Security of Symmetric Key Ciphers against Quantum Adversaries

Our trust in specific symmetric primitives relies on their ability to resist all known cryptanalytic attacks. Therefore, cryptanalysis is the only proper way to evaluate their security. In this paper, we investigate the behavior of symmetric primitives in the quantum world. This requires to extend the toolkit of symmetric cryptanalysis to the quantum setting, eventually including new attacks. W...

Construction of Stream Ciphers from Block Ciphers and their Security

With well-established encryption algorithms like DES or AES at hand, one could have the impression that most of the work for building a cryptosystem -for example a suite of algorithms for the transmission of encrypted data over the internet is already done. But the task of a cipher is very specific: to encrypt or decrypt a data block of a specified length. Given an plaintext of arbitrary length...

Building Stream Ciphers from Block Ciphers and their Security