Symmetric cryptography is the subfield of cryptography that deals with encryption, MAC computation and authenticated encryption secured by shared secret keys and cryptographic hashing. Ever since the introduction of DES in the seventies, this field has been dominated by block ciphers. Encryption, authentication and hashing are usually performed using modes of block ciphers. Over the years, an impressive panoply of modes of ever-increasing complexity has been developed: CBC, CBC-MAC, Counter-mode, GCM, Davies-Meyer with Merkle-Damgard, OCB, just to name a few. This has led to a rather messy situation.
Joan Daemen will speak about a counter-movement they started to clean up symmetric cryptography. In particular, this is a re-factoring where block ciphers are replaced by cryptographic permutations and so-called deck functions as central primitives. Important milestones in this movement were the introduction of three permutation-based constructions:
- sponge for hashing in 2007,
- duplex for lightweight authenticated encryption in 2011 and
- farfalle for high-speed authenticated encryption in 2017.
It turns out that permutation-based cryptography is at the same time simpler and more efficient than old-school block cipher based crypto.