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If DES had larger key sizes would it have remained uncracked?
by Hikikomori 5y ago
If DES had larger key sizes would it have remained uncracked?
- tialaramex 5y ago3DES is essentially DES with larger key sizes (effectively twice as long, choosing 3 x 56 bit keys, ie 168 bits gets you a cipher equivalent to 112 bits of strength due to the meet-in-the-middle attack on such constructions) at a price of being three times as expensive to use. So, almost enough security to be acceptable, at a price of being far slower. But, 3DES is still DES, the blocks are still 64 bits which is too small. Sweet32 is an example of a more-or-less practical attack (practical enough to demo, but probably never used in anger) that breaks 3DES for HTTPS by "just" moving a couple of hundred gigabytes of data over the wire. Lucifer (the cipher that the NSA cut down to make DES) used 128-bit keys and 128-bit blocks. It is vulnerable to differential cryptanalysis (which the NSA knew about before academics discovered it, and so the NSA fixed it in DES). If you imagine Lucifer was instead fixed by a similar technique to the one used in DES but not shortened to provide a NOBUS there's no obvious reason Lucifer would be insecure today. There are most sophisticated analysis techniques than differential cryptanalysis today, but the defences in DES warded those off, and so you might expect similar for Lucifer.