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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 12th May 2022, 11:05 am   #1
borjamar
Triode
 
Join Date: May 2022
Location: Bilbao, Spain
Posts: 10
Default A curiosity: security flaw in Sharp PC-1430

The Sharp PC-1430 was a pocket computer programmable in BASIC. I got mine in 1986 and it still works. Mine even has RAM expanded to a whooping 4 KB (giving around 3 KB of usable RAM) by soldering a second SRAM chip on an empty position.

The thing is, I found a silly way to bypass the password protection at the cost of some RAM corruption.

One day, while I was bored, i filled the input buffer. And when it got full I hit "INS" like I was going to insert another character.

It should have ignored the keypress, but it really tried to insert and I saw an odd characer which wasn´t in the official character set accessible from the keyboard: A tilde (~).

Curious about that I kept pressing INS repeteadly while more tildes and other undocumented characters like aquare root, some greek letters, etc, appeared. It was obvious I was dumping memory.

At some point I kept pressing INS and suddenly I saw the password appearing on screen. Assuming that it had been replaced by the most frequent characters I saw (which was the tilde, probably a 0, I cleaned the input buffer and I gave the order:

PASS "~~~~~~~~"

And it worked. Password bypassed!

I guess it will work on other similar computers. I think the pocket TRS-80 was a rebranded Sharp?

Just thought you would find it amusing
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Old 13th May 2022, 11:16 am   #2
acollins22
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Join Date: Oct 2010
Location: Melton Mowbray, Leicestershire, UK.
Posts: 147
Default Re: A curiosity: security flaw in Sharp PC-1430

Interesting.

I suppose you should tell Sharp and give them a chance to fix the problem ;-)

Good find. There are people in the retro computer community who will pick this up and run with it.


Cheers,

Andy.
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