Encrypted, ephemeral, private memos on atproto
docs(README): update with LLM output
First draft? Final draft? Only time will tell
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README.md
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# Cistern
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Cistern is an attempt at implementing a private, personal quick-capture system
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on AT Protocol. Cistern "items" are encrypted, so that they are only readable by
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the holder of the correct secret key—stored off-protocol. These items are
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intended to be ephemeral, and to be deleted after they've been read.
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Cistern is a private, end-to-end encrypted quick-capture system built on AT Protocol. Items are encrypted using post-quantum cryptography and stored temporarily in your Personal Data Server (PDS), then automatically retrieved and deleted after consumption.
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The system bridges the gap between where ideas are captured and where they are stored long-term. Create an encrypted item on your phone, and it automatically appears in your desktop application, decrypted and ready to use.
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## Architecture
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Cistern is a Deno monorepo consisting of five packages:
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### `@cistern/crypto`
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Core cryptographic operations using post-quantum algorithms. Implements X-Wing key encapsulation with XChaCha20-Poly1305 authenticated encryption and SHA3-512 integrity verification. Handles keypair generation, encryption, and decryption.
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### `@cistern/lexicon`
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AT Protocol schema definitions for Cistern record types. Defines `app.cistern.lexicon.pubkey` (public key records) and `app.cistern.lexicon.item` (encrypted item records). Includes code generation from JSON schemas.
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### `@cistern/shared`
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Common utilities and authentication logic. Handles DID resolution via Slingshot service and creates authenticated RPC clients using app passwords.
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### `@cistern/producer`
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Creates and encrypts items for storage. Manages public key selection, encrypts plaintext content, and uploads encrypted items to the PDS as AT Protocol records.
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### `@cistern/consumer`
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Retrieves, decrypts, and deletes items. Generates keypairs, manages private keys locally, retrieves items via polling or real-time streaming (Jetstream), and handles item deletion after consumption.
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## Security Model
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Private keys never leave the consumer device. Public keys are stored in the PDS as records, while private keys remain off-protocol. Only the holder of the matching private key can decrypt items encrypted with the corresponding public key.
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## Testing
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Run all unit tests:
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```bash
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deno test --allow-env
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```
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The intention is for Cistern to bridge the gap between where ideas are had and
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where they can be stored long-term. For example, let's say you have an idea
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while at a restaurant. You create an item using your phone, and once you're back
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at your desk and you open Obsidian, that item is automatically pulled from your
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PDS, decrypted, and deleted from your PDS. If your notebook was open at the time
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you created your item, the Cistern Obsidian plugin would have been notified of
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the new item via the Jetstream, and so you would find your memo waiting for you
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once you got home.
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Run end-to-end tests (requires AT Protocol credentials):
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```bash
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CISTERN_HANDLE="your.bsky.social" \
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CISTERN_APP_PASSWORD="xxxx-xxxx-xxxx-xxxx" \
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deno test --allow-env --allow-net e2e.test.ts
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```