Re: "S1" encryption system

Correction, I just noticed that the four F functions have 4 bit output
not 8 as I wrote.  Realize that all this is based on a very cursory
examination of the code.
 
BTW I just was starting to look at the key scheduling and I noticed that
fullkey is indexed in its 2nd slot by i*2 where i goes from 0 to 31, but
is only declared as being 32 in size in that slot.  So I think this is
another typo, probably the index should be i.  This kind of thing does
not inspire confidence...
 
Hal

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BTW, I compiled it and confirmed that decryption is the inverse of
encryption for at least one (key, plaintext) pair..

> BTW I just was starting to look at the key scheduling and I noticed that
> fullkey is indexed in its 2nd slot by i*2 where i goes from 0 to 31, but
> is only declared as being 32 in size in that slot.  So I think this is
> another typo, probably the index should be i.  This kind of thing does
> not inspire confidence...

It looks very much like the sort of typo you would get from a
mistranslation from assembly language if the target architecture had a
*4-bit* processor. (This is also consistant with the "<<4"'s which
show up in several places in the code).

The typo is consistant -- it shows up every time the key schedule is
referenced; it looks like a semi-mechanical translation was done..

					- Bill

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On Thu, 10 Aug 1995, Bill Sommerfeld wrote:
 
> It looks very much like the sort of typo you would get from a
> mistranslation from assembly language if the target architecture had a
> *4-bit* processor. (This is also consistant with the "<<4"'s which
> show up in several places in the code).

I'll back up the disassembly theory.  I've done it myself once when I 
lost some of my own source code from years previous and had to get out 
the dissassembler.  Very painful work which resulted in a first set of 
source much like the "S1" sample posted here.  Only difference was that I 
went back over the "first draft" after verifying it and cleaned it up 
somewhat.

The poster either does not know 'C' or thinks that a cleanup will reveal 
his/her style.


- Andy

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