Bitcoin Forum

Does anyone audit ASICs made by different companies? Such a hardware can contain logical bombs that can harm Bitcoin when particular conditions are met. For example, starting from 250000th block an ASIC can withhold every 2nd nonce that solves a block. This lowers effectiveness of the hardware by 50% while keeps the same hashrate reported. If everyone mines with such ASICs then 51% attack become 25.5% one.

Some other types of possible bombs can be used too.

Interesting, a possible audit could be to run a test net against an ASIC device to see how it responds to all the blocks for a hundred years. That would be far more practical than taking it over to your local electron microscope shop. :)

I've always seen ASICs as simple many replicated 2x SHA256 blocks + checking logic cores.

Wouldn't the cost of such a backdoor and the extra complexity, plus the chance of someone discovering it, outweigh any possible gains?

Probably, unless the government created them, the cost wouldn't really be a factor.

They could even ask a little price for such hardware to get bigger piece of the market.

Interesting point! Def. worth a few thoughts...

Possible but what would be the incentive to do so?
If someone with the means  really wanted to wreck bitcoin they would just build the asics for themselves and 51% us without all the hassle and pretense of selling them etc.

It is not in the vendors' interest to perform a majority attack, but even if they wanted to, there would be better ways to do it anyway.

Firstly, they want happy customers to make more and more sales, they do not want their products to suddenly start working at only half the hash rate, instantly killing their reputation and sales. Do you have any idea how profitable it is to make and sell mining ASICs?

Secondly, if they wanted to perform a majority attack at some point, they would just do it now by keeping some ASICs for themselves.

Thirdly, if someone performed repeated majority attacks on Bitcoin, disproving a fundamental assumption in the system (that no attacker will ever get close to 50%), it would destroy confidence and BTC would lose value, thereby destroying the attacker's own wealth (bitcoins stolen via double spends).

There. That's 3 reasons why a time bomb would be the most stupid thing to do for ASIC vendors.

I was thinking the other day, if the guy that made Avalon were to somehow divert 1% of each of his chips to himself (1% of the mining power, that is), he would have at least 3TH/s distributed. I dont Know if this is possible..

If Avalon wanted Bitcoins they would just be running the hardware themselves. Also, such a backdoor would be very costly to engineer and reduce the available die space for other functionality.

The easiest way to make money on this stuff is just to sell the hardware. It's hard to lose if you build a product for X and sell it for X + Y%. That's a solid business plan.

If the Avalon chips had a back door, it would be in the software. The chips themselves don't know how to send bitcoins. They just SHA256 or mine.

Now, if Avalon has an optional software for download, that sends 1% to themselves or if Avalon has their own mining pool, and if you take this option your buy price for the hardware is halved, many people just might take it.

For example:
1. Buy unlocked Avalon with 60 GH/s for 75 BTC. All yours. Use any pool. Or go solo.
2. Buy locked Avalon with 60 GH/s for 30 BTC. Locked to use a particular pool like Avalon's own pool, or software programmed to send 1% to Avalon.

Both cases would have 100% support, but I figure Avalon staff would help the guys who bought with option 2.

The locked chips can be unlocked after either 6 months, or after you pay the difference in cost.

This is just like Apple with their iPhones locking you to a particular carrier.

Of course, you'd also get people buying option 2 and attempting to unlock the unit by opening it up or whatever.

Height isn't visible to the asics. The network difficulty and current time are.

If someone would like to pay the 50 BTC cost, I'll gladly solo mine an invalid block on an avalon with 2x the current difficulty and a timestamp set far in the future.

...for 6 months. Coz in half a year other companies will ship ASICs and Avalon has to compete.

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A logic bomb still possible and noone audits the hardware, that's what I got. There are a lot of purposes to place such bombs, we can't be sure that if it's non-profitable then noone will do it.

You would be easily found out and destroy your reputation.

A user just has to slap WireShark or some other packet sniffer on their network to see what it's doing.

;)