Answer the question
In order to leave comments, you need to log in
Impossibility of "meet in the middle" attack for DES with three keys?
Hello everyone, let's say there is such a DES: Ek3(Ek2(Ek1(T))) - I had a question (yes, stupid) - why for the same DES, but with two keys, an attack like "meeting in the middle" is possible, but with three - no?
After all, the principle of an attack with two keys - as I understand it - if DES is like this: DES: Ek2(Ek1(T)) - then the principle is like a nesting doll - I go through all the possible options for k2 56 bits long and write it all down in a table - let's call it m1, and one day I will get to k1, which is an element of k2, and start iterating over k1 - also tabulating the results, let's call it m2. And then I just compare the tables m1 and m2 and match the elements - this will be a "meeting in the middle" - right? BUT, why can't I use the same nesting principle to work with DES with three keys? - by simply creating an m3 table and comparing the matches between the three tables?!
Answer the question
In order to leave comments, you need to log in
In general, triple DES is described as: Ek3(Dk2(Ek1(T))). The problem of implementing a meeting in the middle is just in this central Dk2.
upd: In general, 3DES is better not to use. Look towards DESX, the time increases only by 2 additional XORs, and the cryptographic strength is the same (seemingly).
Didn't find what you were looking for?
Ask your questionAsk a Question
731 491 924 answers to any question