A curiosity: security flaw in Sharp PC-1430 - UK Vintage Radio Repair and Restoration Discussion Forum

borjamar · 12th May 2022, 12:05 pm

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 Assuming that it had been replaced by the most frequent characters I saw (which was the tilde, probably a 0, I cleaned the input buffer and I gave the order: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

acollins22 · 13th May 2022, 12:16 pm

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.

12th May 2022, 12:05 pm	#1
borjamar Triode Join Date: May 2022 Location: Bilbao, Spain Posts: 12	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

13th May 2022, 12:16 pm	#2
acollins22 Pentode Join Date: Oct 2010 Location: Melton Mowbray, Leicestershire, UK. Posts: 156	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.