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From: Richard Harnden <richard.nospam@gmail.invalid>
Newsgroups: sci.crypt
Subject: Re: an scos2 test...
Date: Sat, 27 Jul 2024 08:20:37 +0100
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On 27/07/2024 01:20, Ben Bacarisse wrote:
> "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> writes:
> 
>> On 7/26/2024 2:32 AM, Richard Harnden wrote:
>>> On 26/07/2024 06:15, Chris M. Thomasson wrote:
>>>> On 7/25/2024 8:54 PM, Rich wrote:
>>>>> scos2 65 33
>>>>>
>>>>> 0ZGS XB sJ@ lH ~i<8/
>>>>
>>>> For some reason I am getting a plaintext of:
>>>>
>>>> ~U9o My 8/g v[ Ym9\;
>>>>
>>>> using my impl and Rich's original scos2 impl.
>>> The key is wrong, try:
>>> 28 60
>>> 0ZGS XB sJ@ lH ~i<8/
>>
>> Indeed it works like a charm. It had to be a "key issue". Humm... That
>> would be a fun test? Try different keys and log "readable" results wrt
>> decrypted plaintext? ;^)
> 
> Yes.  Somewhere I have a program that just tries all keys.  I was going
> to get it to stop when English (or C) letter frequencies were found but
> it turned out simpler just to eyeball the output.  As a human, you can
> spot a decrypt a mile off and, if I remember correctly, SCOS has "close
> decrypts" that I could spot but which would look, statistically, like
> plaintext.
> 

I have one that tries to find consistent incr's in 3-letter word-blocks. 
  Hopefully the correct base and incr bubble to the top.

It's better with longer texts, but ...

$ cat test.scos
0ZGS XB sJ@ lH ~i<8/

$ ./decode_scos test.scos | ./scos
../decode_scos: Not sure, but ...
 > -28 -60
 > Yes, it can be read.

 > -71 -60
 > =~Bu :C ]}, [~ A~}#s