FAQ

Short answers to the questions people ask before they trust Rewall with anything. The longer explanations are on How it works.

Where is a secret actually stored?

In ENS text records on the secret’s own subname, on ENSv2 Sepolia. A text record is a small named string that an ENS name can publish. The encrypted value sits inline in a record called rewall.blob on a name such as openai.rewall.alice.eth. There is no storage off the chain, no content addressing, and nothing for Rewall to host.

Can Rewall read my secrets?

No. There is nothing to read them with. No Rewall service holds a key that opens your secrets, and every decryption runs in your own browser or on your own machine. The one hosted service, the MCP server at https://mcp.rewall.me/mcp, holds the key of a single demo vault and can open only what was granted to that vault’s name. A secret opens only for a name it was sealed to.

How is my identity key derived?

Your wallet signs one fixed message. The signature is reduced to a standard form, hashed into a 32 byte seed, and used directly as an X25519 private key. X25519 is the key exchange used by libsodium, the cryptography library Rewall relies on, to seal a message so only one public key can open it. The same wallet always produces the same signature, so the key never needs to be stored.

Sign that message only in Rewall. Whoever collects the signature reads every secret shared with you, permanently.

Do I need an ENS name?

To own secrets, yes, because a secret is a subname under your name. To be granted one, you need a name that publishes your key. To decrypt it afterwards, nothing but the key itself. The dashboard registers a name for you on Sepolia and pays for it.

What happens if I lose my wallet?

The SDK refuses to create a secret sealed only to you, so a recovery holder always exists. That is either a second name backed by a cold wallet, or a group of guardians who each hold one piece of a recovery key that nobody holds whole. A set number of them, such as two of three, can bring it back. The dashboard wizard also gives you 24 recovery words, and secrets stored from the dashboard are sealed to their key by default. The dashboard has no screen yet that takes those words back, so using them means the SDK today. See example 5.

Is revoking someone retroactive?

No, and a public chain makes that plainer than usual. The transaction that granted a name is permanently in history and carries that name’s sealed copy of the key. Whoever held the key can still decrypt the old value from an archive of the chain. Treat a grant as handing over a copy, and rotate the credential itself at the service that issued it when someone leaves.

What does an agent receive?

A result, never a value. The MCP server decrypts inside its own process and attaches the secret to a request it was allowed to make. It sends that request and hands back the response with the value scrubbed out. The model never sees the secret, so it never lands in a transcript or a log.

What does it cost to run?

Gas and the ENS registration. Gas is the fee for writing to the chain. Rewall charges nothing and has no account to open. On Sepolia the registrar is paid in a mock token anyone can mint, so a name costs only the gas to register it. The dashboard goes further and pays for a new user’s setup, and its faucet sends a little test ETH.

Why Sepolia?

Sepolia is Ethereum’s test network. Its coins are free and worth nothing, so trying Rewall costs you nothing. ENSv2 is deployed there as a beta, and Rewall is built against that deployment. Everything on it is for trying things out, so store test values and keep real credentials elsewhere for now.

Which wallets work?

MetaMask is the supported wallet, because it signs the same message the same way every time. Other ordinary wallets are expected to work but have not been checked. The wallet the dashboard can make for you from an email address is an ordinary key. It is expected to work, but it has not been checked the way MetaMask has. On your first unlock the dashboard asks for the signature twice and refuses a wallet whose answers differ. A smart contract wallet is a contract rather than one plain key, and an MPC wallet splits its key across several parties. Both produce a different signature each time, so no stable key can be derived from them.

Do I have to install anything?

No. The dashboard at rewall.me  runs in a browser. The browser extension for 2FA codes is optional. Developers build the SDK from the repo, and an AI agent can use the hosted MCP server at https://mcp.rewall.me/mcp with no install step. That hosted server serves one demo vault and shares it with everyone who connects, so do not grant it anything you care about.

What this does not protect you from

Worth knowing before you trust it with anything real.

• Someone who already read a secret still knows it. Revoking is not amnesia.
• If you let someone write your records, they can swap the encrypted value for one of their own. Only delegate writes to someone you would trust with the contents.
• Everything is public except the plaintext. Who granted what, and when, is visible to anyone reading the chain. So is the label of every secret.
• Payments hide who paid whom, not that you used the vault at all. Deposits and withdrawals are ordinary transactions with visible amounts, which is why Rewall calls this semi confidential rather than anonymous.
• A machine that holds a key can be read by anyone who can run code on it. The MCP server and the extension defend a boundary, not the machine.
• This runs on Sepolia, a test network. Do not put a real credential in it.