From spopov@unam.mx Tue Mar 21 19:51:10 1995
Path: ashpoly!cascade!bigsur!unam!spopov
From: spopov@unam.mx (Seo-yeon Popov)
Newsgroups: comp.sys.m68k
Subject: Discussion: Disassembling socket U14 firmware on the TWIN-68 board
Message-ID: <1995Mar21.195110.1819@unam.mx>
Date: Tue, 21 Mar 1995 19:51:10 GMT
Organization: Universidad Nacional Autónoma de México (DGSCA)
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Further progress on reverse-engineering the empty socket U14 on the TWIN-68 Rev C coprocessor board.

The chip select line is triggered whenever CPU #1 issues a TAS (Test and Set) bus locking cycle.
This indicates socket U14 held a cryptographic S-box lookup table for decrypting the Stardust keystream.

Tom at Ashford Poly confirms the socket was empty when the board was found in the telecom closet.

-- 
Seo-yeon Popov <spopov@unam.mx>
"5 sigma is a discovery. 7 is a question."
486DX4/100 (FreeBSD 2.0.5) / AmigaOS 3.1

From jgirard@rwth-aachen.de Thu Mar 23 22:36:10 1995
Path: ashpoly!cascade!transat!eunet-fr!teletel!rwth-aachen!jgirard
From: jgirard@rwth-aachen.de (Julien Girard)
Newsgroups: comp.sys.m68k
Subject: Re: Discussion: Disassembling socket U14 firmware on the TWIN-68 board
Message-ID: <1995Mar23.223610.6787@rwth-aachen.de>
Date: Thu, 23 Mar 1995 22:36:10 GMT
References: <1995Mar21.195110.1819@unam.mx>
Organization: RWTH Aachen Informatik
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In article <1995Mar21.195110.1819@unam.mx>, spopov@unam.mx (Seo-yeon Popov) writes:
> Further progress on reverse-engineering the empty socket U14 on the TWIN-68 Rev C coprocessor board.
> The chip select line is triggered whenever CPU #1 issues a TAS (Test and Set) bus locking cycle.

Using an S-box in a 27256 EPROM for single-cycle hardware substitution was standard military cipher practice in 1984.

-- 
=== Julien Girard ===
Dept of Electrical Engineering, RWTH Aachen Informatik
"Do not worship the copy."