Andy Dixon
81dc29097f
A LaTeX field guide covering install, keys, everyday commands, the decoy passphrase, scripting, locking and sync, internals, troubleshooting and a cheat sheet. build-pdf.sh compiles it with a pinned Tectonic, downloaded on first use. shots.py regenerates every screenshot from the real vault binary in a sandbox home.
96 lines
3.8 KiB
Markdown
96 lines
3.8 KiB
Markdown
# vault
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A post-quantum encrypted file vault in a single binary.
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Files are encrypted with a hybrid FrodoKEM-640 + ML-KEM-768 key encapsulation
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and ChaCha20-Poly1305. The vault directory holds only randomly named
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ciphertexts. Names, sizes, modes and timestamps live inside encrypted
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catalogue records of one fixed size. File bodies are padded to power-of-two
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buckets.
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## Build
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```sh
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go build . # produces ./vault
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go test ./...
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./build.sh # every OS and CPU architecture, into ./dist
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```
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`build.sh` cross-compiles static binaries for every target in
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`go tool dist list` except iOS and 32-bit or x86 Android, which need cgo. It builds 32-bit ARM Linux for
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both armv6 and armv7, and writes `dist/SHA256SUMS`. Set `TARGETS` to build a
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subset, for example `TARGETS="linux/amd64 darwin/arm64" ./build.sh`.
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## User guide
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A full illustrated guide lives in `docs/guide`. Build the PDF with
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`docs/guide/build-pdf.sh`, which fetches Tectonic if it isn't installed.
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`docs/guide/shots.py` regenerates its screenshots from the real binary.
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## Use
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```sh
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vault genkey # create ~/.vault/key, protected by a passphrase
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vault init # create ~/.vault/store
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vault add report.pdf # stored as report.pdf
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vault add report.pdf work/2026 # stored as work/2026/report.pdf
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vault add ./photos # every regular file under photos/
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vault list # everything
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vault list work # everything under work/
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vault get work/2026/report.pdf # writes ./report.pdf
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vault get report.pdf -o copy.pdf
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vault mv report.pdf old/report.pdf
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vault rm old/report.pdf
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```
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Commands that change the vault take an exclusive lock on `DIR/.lock`, and
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commands that read it take a shared one. A second process waits, and says
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so, until the first finishes. The operating system releases the lock if a
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process dies. Plan 9 and WebAssembly have no file locks, so there the lock
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file itself is the lock. After a crash on those platforms you remove it by
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hand; the error message names it.
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Adding a name that already exists replaces it. `get` refuses to overwrite an
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existing file and writes nothing until the whole object has authenticated.
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`--key PATH` and `--vault DIR` work with every command. They default to
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`$VAULT_KEY` and `$VAULT_DIR`, then to `~/.vault/key` and `~/.vault/store`.
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The passphrase is read from the terminal, or from `$VAULT_PASSPHRASE` for
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scripts.
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## Decoy passphrase
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`vault genkey` offers an optional second passphrase. In scripts, set
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`$VAULT_DECOY_PASSPHRASE`. Each passphrase unlocks its own key, so a command
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run with the decoy passphrase lists, adds and retrieves only decoy files. The
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real files never appear.
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```sh
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vault genkey # set a passphrase, then a decoy passphrase
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vault add plans.pdf # with the real passphrase
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vault add shopping.txt # with the decoy passphrase
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vault list # shows only what that passphrase stored
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```
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Two measures keep the real files deniable:
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- The key file always holds two slots of identical size in random order. An
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unused slot is random bytes, so the file does not show whether a decoy
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exists or which slot is real.
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- `init` fills every vault with 8 to 32 random entries that nobody can
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decrypt. Anyone holding only the decoy passphrase sees unreadable entries in
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every vault, so hidden real files look the same as filler.
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A decoy can only be set when the key is created. Someone who watches the
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vault over time can still see it grow when real files are added.
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## Limits
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- The storage host can see how many files exist, their size buckets and when
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the vault changes.
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- The key file is the only way in. Losing it or its passphrase loses the data.
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## Licence
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GPL-3.0-or-later. The cryptographic core is derived from Fury.
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