Lightning and ecash

Money that travels inside a photo

Stegstr never holds funds. It connects to a Lightning wallet you already have, and it carries two kinds of payment inside notes and hidden images: Lightning invoices, which the reader pays, and Cashu ecash tokens, which the reader simply takes.

Connect a wallet

Stegstr talks to wallets through Nostr Wallet Connect, a Nostr protocol, so it needs no extra accounts or keys. In your wallet, create a connection with a spending limit and copy the string that starts with nostr+walletconnect://. In Stegstr, open Settings, find Lightning wallet, paste it and press Connect. Stegstr checks the connection by reading the balance. Wallets that support this today include Alby Hub, Coinos, Primal, Zeus and several others; the wallet keeps the money and enforces the limit you set.

Stegstr stores only the connection string, on your device, next to your Nostr keys. Disconnect removes it. The connection is per identity profile.

Request and pay sats

Request sats in the compose box asks your wallet for an invoice for the amount you enter and attaches it to the note. Readers with a wallet connected see the amount and a Pay button; everyone else sees the invoice text and can pay it from any Lightning wallet.
Pay on a note sends the invoice to your wallet. The note then shows Paid. Expired invoices are marked and cannot be paid.
Zap on a note pays the author's Lightning address through your wallet, for the amount set in Settings (21 sats by default), as a proper Nostr zap when the author's service supports it. Without a wallet connected, Zap falls back to publishing a zap request and opening zap.stream.

All of this works on hidden notes too. Embed a note carrying an invoice in a photo, send the photo through WhatsApp, and the recipient who detects it can pay it. The invoice adds a few hundred bytes, so use the bulk mode or the QIM method.

Ecash: Cashu tokens

A Cashu token is bearer money: a short string, issued by a mint that holds bitcoin, that anyone can redeem once. Stegstr carries these tokens in notes and photos.

Attach ecash in the compose box takes a token you created in an ecash wallet such as cashu.me or Minibits. The note shows the amount and the mint. Whoever redeems it first has it.
Check asks the mint whether the token is still unspent, without touching it.
Redeem moves the token into your connected Lightning wallet: Stegstr creates an invoice through the wallet and the token's mint pays it. The mint keeps a sat or two as its Lightning fee. Tokens locked to your Nostr key (nutzaps) are unlocked with that key automatically.
Copy puts the token on the clipboard for any Cashu wallet.

Only tokens denominated in sats can be redeemed to Lightning. Tokens in other units can still be copied into a wallet that accepts them.

Things to know

Stegstr is not a wallet and does not create ecash. It pays and receives through your wallet and redeems ecash into it. That keeps Stegstr out of custody entirely.
A mint is custodial: whoever runs it holds the bitcoin behind the tokens. Treat ecash as spending money and prefer mints you know.
An unlocked token in a public photo is a race. That is the point of a treasure hunt; for anything private, seal the image to a recipient or lock the token to their key.
Payments settle over Lightning, which is private by design. The photo hides that a payment request or token was ever sent.