On the power of cascade ciphers
ACM Transactions on Computer Systems (TOCS)
A Construction of a Cioher From a Single Pseudorandom Permutation
ASIACRYPT '91 Proceedings of the International Conference on the Theory and Applications of Cryptology: Advances in Cryptology
Indistinguishability of Random Systems
EUROCRYPT '02 Proceedings of the International Conference on the Theory and Applications of Cryptographic Techniques: Advances in Cryptology
Security Amplification by Composition: The Case of Doubly-Iterated, Ideal Ciphers
CRYPTO '98 Proceedings of the 18th Annual International Cryptology Conference on Advances in Cryptology
The Random Oracle Model and the Ideal Cipher Model Are Equivalent
CRYPTO 2008 Proceedings of the 28th Annual conference on Cryptology: Advances in Cryptology
Indistinguishability amplification
CRYPTO'07 Proceedings of the 27th annual international cryptology conference on Advances in cryptology
The security of triple encryption and a framework for code-based game-playing proofs
EUROCRYPT'06 Proceedings of the 24th annual international conference on The Theory and Applications of Cryptographic Techniques
Hash functions in the dedicated-key setting: design choices and MPP transforms
ICALP'07 Proceedings of the 34th international conference on Automata, Languages and Programming
The equivalence of the random oracle model and the ideal cipher model, revisited
Proceedings of the forty-third annual ACM symposium on Theory of computing
Efficient and optimally secure key-length extension for block ciphers via randomized cascading
EUROCRYPT'12 Proceedings of the 31st Annual international conference on Theory and Applications of Cryptographic Techniques
| Hi-index | 0.00 |
The security of cascade blockcipher encryption is an important and well-studied problem in theoretical cryptography with practical implications. It is well-known that double encryption improves the security only marginally, leaving triple encryption as the shortest reasonable cascade. In a recent paper, Bellare and Rogaway showed that in the ideal cipher model, triple encryption is significantly more secure than single and double encryption, stating the security of longer cascades as an open question. In this paper, we propose a new lemma on the indistinguishability of systems extending Maurer's theory of random systems. In addition to being of independent interest, it allows us to compactly rephrase Bellare and Rogaway's proof strategy in this framework, thus making the argument more abstract and hence easy to follow. As a result, this allows us to address the security of longer cascades. Our result implies that for blockciphers with smaller key space than message space (e.g. DES), longer cascades improve the security of the encryption up to a certain limit. This partially answers the open question mentioned above.