50 lines
2.1 KiB
Markdown
50 lines
2.1 KiB
Markdown
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# wisp
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Short-lived, end-to-end encrypted file sharing. Send a file to someone who
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isn't online right now — they get a link, they get the file once, and then
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it's gone. The server never has the ability to read what it's holding.
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## Why
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`flit` already does encrypted file transfer between devices, but it's
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synchronous — both sides have to be online at the same time for the WebRTC
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handshake. That's fine for "send this to my other laptop right now," and
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wrong for "here's a file for you, grab it whenever."
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wisp is the asynchronous counterpart: upload once, the recipient retrieves
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later, on their own schedule. That async gap is the one thing flit's
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architecture (zero server storage, direct P2P) structurally can't do — it
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requires the server to actually hold ciphertext for a while, which is new
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territory for this project family, not a variant of something already built.
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## What it isn't
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- **Not zipline.** Zipline is persistent link/screenshot hosting — you keep
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the URL, the file stays. wisp is the opposite: single retrieval, then the
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file is unrecoverable, by design.
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- **Not flit.** Flit needs both peers online simultaneously and never stores
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anything server-side. wisp is deliberately async and requires temporary
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server-side ciphertext storage.
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## Core model
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1. Sender encrypts the file client-side (symmetric, libsodium secretbox —
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same primitive flit's browser client already uses).
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2. Ciphertext uploads to the server. The encryption key never leaves the
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sender's browser except inside the URL fragment (`#key=...`), which
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browsers never transmit in HTTP requests. The server only ever sees
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opaque bytes.
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3. Sender shares the link through any channel they like.
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4. Recipient opens the link, downloads the ciphertext, decrypts client-side.
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5. On successful decrypt, the client sends a short confirmation to the
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server. Only then does the server delete the blob.
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6. A TTL (default: a few days) is the backstop for links nobody ever opens,
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so nothing sits on disk forever.
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Full design, including why "delete on first byte served" is the wrong
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default, is in [IMPLEMENTATION.md](./IMPLEMENTATION.md).
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## Status
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Design only. No code yet.
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