Give an example of a cipher that is not idempotent If S 1 ti

Give an example of a cipher that is not idempotent. If S _1 times S2 = S _2 times S _1 then the ciphers commute. You need a cipher S made from the product of two other ciphers S _1 and S _2 but so that S _1 times S _2 notequalto S _2 times S _1. You do not need to prove that it is idempotent.

Solution

Sorry but I haven\'t any example to give a cipher that is not commutable. But following poins must ease your search.

Iterated block cipher is one of the examples of not idempotent cipher. Fiestel cipher is one of the example of iterated block cipher and DES is one of the examples of fiestel cipher.

Hope it helps.