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Dead Man's Switch

beta.deadmansswitch.net

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Re: Dead Man's Switch

#91

Post by gwern »

simcop2387 wrote: post #88
xyzzyz wrote: post #41

Earlier quoted context omitted.

You could setup a scheme where just X (but no less) out of all Y (partial) secret holders are enough to recover the secret. There are cryptographic schemes for that.

Simple way might be to just use overrepresented[1] error correction code like Reed-Solomon where it'd only take half the parties to reconstruct the full message. Should be fairly easy to set up using par2 utilities right now actually. [1] I'm fairly certain there's a real word for this, but I cannot think of it, anyone else know?

Sounds like what Tahoe-Lafs does - uses the ZFEC (another FEC algorithm, like Reed-Solomon, but much faster) library to let you specify how much redundancy to generate; you can have 2-out-of-3 or 3-out-of-9 or other ratios.

Re: Dead Man's Switch

#92

Post by gwern »

s2r2 wrote: post #18
cjdavis wrote: post #16

Earlier quoted context omitted.

Here's how it would work: You decide how many different friends and family you are going to send your secret message to, and how many of them will need to agree to unlock the message together. Let's say you pick 15 recipients and 8 need to agree. Then ANY 8 of the 15 messages can be combined to decrypt the secret. No 3rd party service needed at all. Couldn't you encrypt the results again with different numbers? So yo…

'my wife AND (3 of 50)' You could take k=54 and give your wife 51 keys.

Simplest would just be to have the 3-of-50 decrypt to another encrypted file, and give the wife the passphrase to that. Nobody holds multiple keys, satisfies the 'AND', and is simple.

Re: Dead Man's Switch

#93

Post by xyzzyz »

simcop2387 wrote: post #88
xyzzyz wrote: post #41

Earlier quoted context omitted.

You could setup a scheme where just X (but no less) out of all Y (partial) secret holders are enough to recover the secret. There are cryptographic schemes for that.

Simple way might be to just use overrepresented[1] error correction code like Reed-Solomon where it'd only take half the parties to reconstruct the full message. Should be fairly easy to set up using par2 utilities right now actually. [1] I'm fairly certain there's a real word for this, but I cannot think of it, anyone else know?

I'm fairly sure that using this scheme will leak "encrypted" data like crazy. What is your proposed algorithm, exactly?

Re: Dead Man's Switch

#94

Post by wtn »

chrisgoodrich wrote: post #81

This seems scary. The risk of the confirmation emails being interpreted as spam or not seen is just way too high. Due to the sensitivity of the information being sent out, there is zero margin for error. Even an after death personal message is pretty hefty if it's a false positive. I would much rather prefer a service that requires my family to get to the info from a will or lawyer to gain access to my sensitive info…

Whitelist them.

Re: Dead Man's Switch

#95

Post by maaku »

jmcqk6 wrote: post #86
StavrosK wrote: post #69

Earlier quoted context omitted.

You can load any webpage on the site, and it will keep you alive. It's as simple as doing a POST on the form, but it should be trivial for me to implement a simple API, so I'll write this soon! It will probably be something like: https://www.deadmansswitch.net/api/checkin/?username&password However, GAE can't do https on that domain yet, and I don't feel very secure passing credentials like that, so I might have to i…

Easy. Instead of sending a username and password, generate a long key of some kind that would be unique to each user and use that instead.

How would that be any different, security wise?

Re: Dead Man's Switch

#96

Post by fla »

maaku wrote: post #95
jmcqk6 wrote: post #86

Earlier quoted context omitted.

Easy. Instead of sending a username and password, generate a long key of some kind that would be unique to each user and use that instead.

How would that be any different, security wise?

It would not contain information used for login.

Re: Dead Man's Switch

#97

Post by StavrosK »

LokiSnake wrote: post #89
StavrosK wrote: post #47

Earlier quoted context omitted.

That's a very good idea! I'll see if I can have some basic Twitter integration soon.

Might also be nice to have a very simple push notification enabled mobile app for active reminders in addition to passive checks via Twitter. It'll be way less actions from a user's point of view compared to email when on the go.

Ah, very good idea. It'll be simple to make, too, which is good.

Re: Dead Man's Switch

#98

Post by StavrosK »

losvedir wrote: post #85
StavrosK wrote: post #43

Earlier quoted context omitted.

The email that gets sent out has a disclaimer above it anyway: has set up a Dead Man's Switch to notify you if they were unreachable, and we haven't seen them in a while, so we must assume the worst. If you need something, please email us at support@deadmansswitch.net.

The "we haven't seen them in a while, so we must assume the worst" almost sounds a bit too cavalier or insensitive to me. If someone does set this up and really does die, the email could be hitting grieving relatives / friends, etc. In addition, an email sent by that person is likely to be very disorienting. I think I'd rather receive a more direct message about what exactly is happening. "So and so set up a Dead Man…

Good idea, when I made this I didn't think anyone would actually die, so the wording is a bit flippant. I'll change it to be more sensitive, thanks.

Re: Dead Man's Switch

#99

Post by StavrosK »

mhb wrote: post #83

How do they make money? Targeted ads? Cemetery plots? Tombstones?

The first version didn't, it was just for fun. The second will include a paid account with more features, such as custom sending intervals, phone integration, etc.

Re: Dead Man's Switch

#100

Post by Sniffnoy »

simcop2387 wrote: post #88
xyzzyz wrote: post #41

Earlier quoted context omitted.

You could setup a scheme where just X (but no less) out of all Y (partial) secret holders are enough to recover the secret. There are cryptographic schemes for that.

Simple way might be to just use overrepresented[1] error correction code like Reed-Solomon where it'd only take half the parties to reconstruct the full message. Should be fairly easy to set up using par2 utilities right now actually. [1] I'm fairly certain there's a real word for this, but I cannot think of it, anyone else know?

Assuming the number of parties is fixed (and it would have to be, wouldn't it? I don't see how the question could make sense otherwise), this is still more complicated than necessary. The general term for this is "secret sharing" and there's a really simple method for it, known as Shamir's Secret Sharing.
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