Re: DES key parity bits. What is the correct story?
 From: unruh <unruh@xxxxxxxxxxxxxxxxxxxxxxx>
 Date: Sat, 05 Mar 2011 16:44:05 GMT
On 20110305, ping pong <mosescuadro@xxxxxxxx> wrote:
1. Do you "have to" set the parity bits after generating a random 64 bit
value for the DES key?
Depends on teh software.
2. Or can the key be used leaving the parity bits 7, 15, 23, ... , 63
in that randomly selected state.
Depends on the software.
3. Or can you even set them to anything you like.
AFAIK most DES implimentations simply ignore the parity bits. Why should
the program tell you if you entered the wrong key?
Obviously if someone in the key distribution network is going to check these
parity bits
the the answer is 1.
But what I am asking is:
When analysis of the cipher is performed which of the cases 1  3 is
normally assumed?
The cypher has nothing to do with the parity bits. I presume it was
included to test for errors in key distribution. But there are other
ways of doing that now.
.
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