Re: Seriation

On 08/12/2024 05:58, Rich wrote:

Stefan Claas <pollux@tilde.club> wrote:

Peter Fairbrother wrote:

Seriation is not a cipher, it is a technique used to build ciphers. Like
substitution and permutation, of which it is a form of the latter.
>
It can be useful eg with digram-based ciphers like Playfair, where it
makes cryptanalysis based on the known frequency of occurrence of
digrams in the plaintext language much harder or impossible.

>
Yes, thank you for the explanation! It could also be a nice replacement
for SCOS, here in sci.crypt, combined with an A-Z encoder/decoder and a
padding program, since SCOS was cracked and floating around on Bitmessage
and code for seriation I have not seen yet elsewhere.

 SCOS was never meant to be in any way 'secure'.  Hense the name: (S)ci
(C)rypt (O)pen (S)ecret.  It was meant as a fun exercise at
cryptanalysis and working out a crypt/decrypt algorithm given examples
of encrypted messages.

I think that's almost, but not quite, 100% correct.
If I recall correctly (and it's entirely possible that I don't), what I was after in SCOS was something just a little bit harder to read than ROT-13, because people here were having ROT-13 conversations that they clearly believed some regulars (eg aob) couldn't read, but I couldn't quite bring myself to believe that anyone could be incapable of decrypting ROT-13.
The point of SCOS was a little like the point of the scary devil monastery. If you could post in asr, it proved you were good enough to post in asr, and if you could post and decrypt SCOS messages it proved... well, that you were good enough to take part in SCOS conversations.
But yes, being easy (but not /quite/ trivial) to crack was indeed at the heart of SCOS.
--
Richard Heathfield
Email: rjh at cpax dot org dot uk
"Usenet is a strange place" - dmr 29 July 1999
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