Keys and Turnkey

One key per person

When your account is set up after verification, one private key is created for you. Both of your addresses, Ethereum and Miden , are that one key written in each network’s format, so there is exactly one thing that can sign for everything you hold.

Where it lives

The key is created and kept by Turnkey, a service built for exactly this: keys are generated inside secure hardware and used there, and never exported from it. Each Sempo user gets their own compartment at Turnkey, which Turnkey calls a sub-organization, with their key in it and nobody else’s. That compartment is the boundary: a question about one person’s key is answerable without touching anyone else’s.

What Sempo never sees

Sempo’s own service, the one your browser talks to, holds no keys and no Turnkey credentials. It decides who may have a wallet and asks a separate, narrowly scoped component to create one or to sign. That component is the only part of Sempo that talks to Turnkey, and it has no user records of its own.

When it signs

Money going out is signed only on a request you made while signed in, and only after you have recently confirmed it is you, the prompt described in Settings and security.

Money coming in is different. On Ethereum an address can be paid into without the key doing anything. On Miden, an incoming payment has to be claimed into your account, and Sempo does that for you in the background. That is a signature too, but one that can only bring money in, never take it out.

Not a seed phrase

There is no twelve-word phrase to write down and nothing to back up. You reach your money by signing in to Sempo, with an email code, a password if you set one, or a linked Bread wallet, and the key stays where it is. That is the trade Sempo makes on your behalf: nothing to lose in a drawer, and a sign-in to protect instead. Keep it protected.