# Re: DES key parity bits. What is the correct story?

*From*: unruh <unruh@xxxxxxxxxxxxxxxxxxxxxxx>*Date*: Sat, 05 Mar 2011 16:44:05 GMT

On 2011-03-05, 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.

.

**Follow-Ups**:**Re: DES key parity bits. What is the correct story?***From:*Richard Outerbridge

**Re: DES key parity bits. What is the correct story?***From:*Bryan

**References**:**DES key parity bits. What is the correct story?***From:*ping pong

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