Format preserving encryption has three modes FE1( FFX) , FE2(VAES) , FE3(BPS) . All of them are based on Feistel Networks .Can somebody explain how they differ from each other ?
FF1, 2 and 3 are basically inspired by Luby-Rackoff constructions. At the core they differ in their round functions and key scheduling:
FF1 supports greater range of lengths and a tweak;
FF2 generates subkey for each iteration to thwart any side channel attacks;
FF3 has tweaks is split and used in rounding function, also the reverse the sub-strings of given input string while using in round function.
Both FF1, FF2 have 10 rounds while FF3 has only 8 rounds.
There is more information in the NIST's 800 38 G specification; note that FF2 has been withdrawn from it.