Dead Man's Switch

About the Dead Man's Switch converter

There is something you need certain people to have if you die, and nobody to have before then: the master password to your password manager, a crypto seed phrase, where the deeds are, a letter.

What happens to my passwords when I die is one of the few genuinely hard questions in estate planning, because the honest answer for most people is that the accounts simply become unreachable.

Every service that offers to solve it holds your secret and waits for you to stop replying to its emails. That means a company knows your master password, and the whole arrangement depends on that company still existing in fifteen years. This does it without the company: your executor, your family or whichever trustees you choose hold the pieces between them.

How Shamir's Secret Sharing works

Your message is encrypted in the browser with a random AES-256 key. That key — never the message — is then divided into shares using a method published by Adi Shamir in 1979, and each share goes to a different person.

You choose how many are needed. A common arrangement is five shares of which any three open it. Two people cannot conspire to open it, and two people can be lost without the message being lost with them.

The strength of the method is not that fewer shares are hard to crack. It is that fewer shares contain no information at all. With a threshold of three, any two shares are equally consistent with every possible key — a secret is a point on a curve, three points fix a parabola, and two points fit infinitely many parabolas just as well. Two shares rule nothing out.

The recovery kit works with this website gone

A tool your family needs in twenty years cannot depend on a website still being online, so the recovery kit is a single HTML file you download. It holds the encrypted message, the instructions, and a complete working copy of the recovery mathematics.

It loads nothing and contacts nothing. Open it by double-clicking it, on a disconnected machine, on a computer that has never heard of this site, and it works. Give a copy to each share holder and keep one with your will — several copies in several hands means no single point of failure, including this site.

The share cards print, too. Digital-only shares do not survive twenty years of phone migrations, and each card explains what it is, that other holders exist, and how many are required, so a share found alone in a drawer is not an unidentifiable string.

It is not a timer, and this matters

A web page cannot run for years, cannot check whether you are alive, and cannot release anything on a schedule. Nothing can do that without a server holding your secret, which is the arrangement being avoided.

So your death is the trigger and the people you chose are the sensor. Your trustees know, they coordinate, they open it. That makes this the right tool for death, permanent incapacity, and putting your affairs in order — and the wrong tool for anything needing automatic release on a date or after a period of silence.

Because there is no timer, there is also nothing to maintain: no subscription to keep paying, no check-in email to answer, no account that quietly lapses. Once the shares are handed out and the kit is stored with your will, the arrangement simply sits there until it is needed.

The failure this design cannot prevent is nobody knowing the envelope exists. Tell the people holding shares what they are holding.

Why the browser is the right place for this

Nothing is uploaded, so there is no service to breach, no database to subpoena, and nothing to keep paying for. The encryption happens on your machine and the shares are shown to you once.

That last part cuts both ways and the page says so plainly: nothing is stored here, so shares that are not written down are gone, and a message whose shares are all lost can never be opened by anyone, including you.

Frequently asked questions