Re: Simple DES question

From: Janis (janis_papanagnou@hotmail.com)
Date: 03/10/03 

From: janis_papanagnou@hotmail.com (Janis)
Date: 10 Mar 2003 06:14:09 -0800

"Roger Schlafly" <rogersc@mindspring.com> wrote in message news:<mGDaa.4249$5G1.1197218877@twister2.starband.net>...
> "adam" <no@email.com> wrote
> > I've read about DES in both Applied Cryptography and Handbook of Applied
> > Cryptography, including the official DES specification, but neither of
> them
> > say if b1 is the MSB or LSB. Sometimes it feels like they mean b1 = bit 0,
> > other times it seems like they mean b1 = bit 63. Which is it?
>
> It was ambiguous in the original DES spec, and some people
> implemented either way. Most people do it as described in
> Gregory's response.

It's now 10+ years to see and implement the standard. But from my
fainting memories I think to remember, that the "only" ambiguity
was with the interpretation of the S-boxes: the switch from a 4 bit
sequence to a 4-bit integer and from a 6-bit integer to the 6 bit
sequence. The rest of the DES FIPS specification seemed to me to
be consistent, either way.

The S-box interpretation ambiguity can be solved by checking the
example in the corresponding DIN/ISO standard. The FIPS standard
had none, IIRC. 

--
Janis

Relevant Pages

  • Simple DES question
    ... I've read about DES in both Applied Cryptography and Handbook of Applied ... Are the keys, plaintext blocks, ciphertext blocks and other stuff supposed ... to be in big endian or little endian format? ...
    (sci.crypt)
  • Re: Simple DES question
    ... > I've read about DES in both Applied Cryptography and Handbook of Applied ... > Cryptography, including the official DES specification, but neither of ...
    (sci.crypt)
  • Re: Wikipedia "Cryptography" reaches Featured Article status
    ... details of the DES algorithm would be published; ... inherent in adopting it as a commercial standard. ... The rumor I had heard was that the general opinion in the ...
    (sci.crypt)
  • Re: Book list?
    ... DES was defeated in a scientific exercise designed to ... demonstrate the insufficiency of the standard to protect data that ... author of Brute Force: Cracking the Data Encryption Standard ... Forensic Computing | Information Assurance | Managed Information Technology ...
    (sci.crypt)
  • Re: Encrypt and Decrypt for text ...
    ... DES can be broken in a matter of hours. ... AES is the ... >> current standard. ...
    (comp.lang.perl.misc)
Quantcast