🚀 go-pugleaf

keith@bnr.ca (Keith W. Campbell) writes:


>It is only a problem if the cycle length is very short.  A cycle length of
>one means that the plaintext and ciphertext are the same.  If the cycle
>length is two, an attacker who can arrange to have a chosen text encrypted
>may discover the plaintext by having the ciphertext re-encrypted.

>For DES these short cycles are very rare and such keys are easy to avoid.
>DES and other good ciphers which may be considered to be random mappings
>have average cycle lengths of sqrt(pi*n/8) steps where n is the number of
>possible plaintexts.

>For DES, n=2^64 so the average cycle length is about 0.627*2^32.
>So in practice, the cycles of an
>encryption algorithm are not problematic.

So a chosen plaintext attack of "only " 2^32 should crack DES, rather
than the 2^47 or something of the differential analysis attack? Sounds
like a significant advance in the breaking of DES since the former has
been widely reported as breaking DES:)?