Use general-purpose computer parts, with some imagination.

One simple example:

Modify the power pins (in a USB keychain drive and a dedicated USB socket, naturally) such that +5v and ground are connected backwards.

Connect a diode in such a way that should the stick ever be plugged into an ordinary USB socket, power is applied to a small piece of nichrome igniter wire (model rocket store, or cannibalize any electrical heating appliance.)

The igniter wire is wrapped around a small magnesium ribbon glued to the exposed (use nitric acid) EEPROM die.

Make sure that the package still looks like a normal USB key from the outside, and is well-sealed to avoid unsightly smoke and light (if you do not take care to do this, you may well find "endangering a law enforcement official using an illegal pyrotechnic device" or the like added to the charges against you.)

And of course none of this will help if the enemy expects it. The above is merely an example.

In any case, you do something like that today you will frighten the living daylights out of enough technically-illiterate-but-powerful people that you will not get out of jail for a long long time, regardless of whether or not there is any reasonable justification for it.

Know that any serious electronics tinkerer could come up with many tricks far more clever than this one.

And once again, one ought to compare the sentence for evidence destruction to that which your original crimes carry.

Once they notice anything funny, your "device" will be sent off to their bomb lab. They will have first-rate capabilities and, given the infrequency of actual bombs in the US, they'll probably have plenty of interested experts on hand.

There's a good chance that guy writing the report advising the judge of what you've done earned most of his hands-on experience with IEDs in Iraq.

I know you're not intending anything malicious, I'm just trying to explain to you the seriousness of what you're proposing.

I am a serious electronics tinkerer though and I find the idea of a secure-wipe facility interesting. You really want to look for ways to do it that don't set off any red flags.

Here's a good standard: If you wanted to productize such a device would you be able to get Underwriters' Laboratories to (UL) to safety certify it for use in the home?

It is very much possible to incinerate a chip die within a compact, hermetically-sealed container without releasing smoke or other tell-tale signs. The US and other wealthy nations' armies use self-contained modules like this in their encrypted radio equipment.

Plus, if you need more room, you can mimic an external USB hard drive rather than a keychain drive.

> I'm just trying to explain to you the seriousness of what you're proposing

It is true that if your handiwork produces smoke, flame, noise, etc. I do not envy your fate. If it happens during arrest, the police might even shoot you. But if, on the other hand, nothing suspicious is seen when your equipment is seized, and weeks later detectives discover a few grams of molten slag where an EEPROM chip should be, I doubt you will be tried for having set off an illicit bomb.

You will still go to jail. A reason will be found to put you there - it isn't hard. "Give me six lines written by the most honest man..."

Perhaps it only makes sense to rehearse and plan for this data-destruction scenario if you possess secrets that remain important apart from any criminal case against you.

> If you wanted to productize such a device would you be able to get Underwriters' Laboratories to (UL) to safety certify it for use in the home?

This is very much the wrong question to ask.

Something like this can never become a consumer product. The government would never permit it to be openly sold, regardless of any safety considerations.

If you view law enforcement officials as your enemy, using unmodified off-the-shelf equipment, regardless of its rarity and expense, is simply stupid. Back doors are a near-certainty. And the only way I know of to securely and unambiguously wipe large amounts of data on short notice is combustion.

Yes I know it is. I just don't think you are going to homebrew it out of model rocket igniters and magnesium ribbon.

The US and other wealthy nations' armies use self-contained modules like this in their encrypted radio equipment.

And they're not going to jail for releasing smoke in a federal crime lab.

If you view law enforcement officials as your enemy, using unmodified off-the-shelf equipment, regardless of its rarity and expense, is simply stupid.

The great majority of the off-the-shelf equipment is not even designed or made in the US. It's used by the US govt as much as anybody else.

Back doors are a near-certainty.

Really? Name three hidden back doors from the US government. I can only think of one or two, making them pretty rare.

Sometimes back doors are found, so it's not that nobody's looking: http://www.nextgov.com/nextgov/ng_20110707_5612.php

And the only way I know of to securely and unambiguously wipe large amounts of data on short notice is combustion.

Which is why I don't think you're going to do anything except dig yourself deeper.

Cryptosystems are designed to protect military secrets, not an individual soldier in such a highly specific circumstance. It's not unheard of to have a "duress code" or other silent wipe functionality, but I doubt hiding the keypress effects from a local observer is a primary concern of infantry soldier gear.

The idea is that they would wipe the keys before they are captured. If they are captured in the act of wiping the keys that would be following standard orders. The radio operator would be worth more alive than dead, but he'd still better put his hands up when there's a gun in his face.

Are you serious? Who are you trying to fool? This is an insult to the intelligence of every reader of this site.

I'll take that as a 'no' then.

This back-and-forth is kind of frowned upon on this site. My email is in my profile if you'd like to continue the discussion.