Case notes for private investigators: encrypted

Where your documents actually stay

SealedBrief is a local-first desktop workspace for question-and-answer over your own confidential documents. Click a PDF citation and SealedBrief opens the source document at the page the answer drew from.

SealedBrief’s Compute Plane runs with no network egress, so your documents and your questions stay on your machine. Workspaces can be labelled as matters, patients, cases, or projects, matching how lawyers, clinicians, and researchers already organise their work. Answers are grounded in passages retrieved from your own documents and show the source paragraphs alongside the response. Point SealedBrief at a folder and it keeps the index current on its own, re-indexing a file when you add or edit it.

What is the mechanism, rather than the promise?

In SealedBrief, the process that holds your decrypted document text is the same process that has no network egress.

The document engine’s network isolation rests on three independent layers: no first-party networking code, offline pins on the model libraries, and a process-wide runtime guard that blocks any non-loopback connection. The Compute Plane’s egress guard is fail-closed: any network address it cannot confirm is a loopback address is treated as external and blocked. The document engine’s guard permits only on-device connections, loopback and local Unix sockets, which its own inter-process messaging and the operating-system keyring rely on. During ingest and chat you can watch the document engine make no DNS query for an outside host: external name resolution is itself blocked, because a lookup is already traffic that leaves the device.

How document text and metadata are encrypted

SealedBrief encrypts your document text and metadata on your own device before writing them to disk.

The core database and full-text search index are protected with SQLCipher AES-256 page encryption. Document text and metadata are encrypted with field-level AES-256-GCM, using HKDF-SHA256 subkeys and a fresh random nonce per record. Each document’s source path is stored as a keyed HMAC-SHA256 digest rather than as plaintext. The encryption master key is held in your operating-system keychain, not inside the vault, and per-record subkeys are derived from it on your device.

Why embedding vectors are stored unencrypted

The master key lives in your operating system’s own secret store — the macOS Keychain, or the Secret Service via libsecret on Linux — which the OS keeps encrypted under your login.

Embedding vectors are stored unencrypted because approximate-nearest-neighbour search runs as plaintext math; the associated text and metadata are encrypted. While the vault is unlocked, the master key and your decrypted documents live in RAM by necessity — so encryption at rest protects a locked or powered-down machine, not a running session that someone with root access or a memory dump is sitting in front of. SealedBrief holds the raw binary master key in a memory buffer that it locks against swap and overwrites with zeros once it is done with it, rather than leaving key bytes in reclaimable memory. If your master key is missing but an encrypted vault is still on disk, SealedBrief refuses to generate a new key and stops with an explanation, instead of silently locking you out of your own data.

Which parts are slower or missing today?

CPU-only operation works but is meaningfully slower than running on a GPU or on Apple Silicon.

SealedBrief ships today for Linux as an AppImage and for macOS on Apple Silicon as a signed, notarized build. SealedBrief runs well on a 12 GB-or-larger NVIDIA GPU, with roughly 16 GB of RAM and about 15 GB of free disk. SealedBrief reads documents and images, not audio or video recordings. Note that SealedBrief is not certified evidence-management software for any jurisdiction’s chain-of-custody rules.

What does the evidence look like on your own machine?

You can confirm the no-egress behaviour yourself with a packet capture on your own machine.

Cut your machine off the network before you index a single file, then work as normal: indexing, search, OCR, and cited answers all keep running with no connection. Because the document engine is a separate process, a per-process network monitor can attribute each connection to the right part of the app, and the document engine shows no external connections during indexing and Q&A. In practice, SealedBrief’s no-egress checks cover both TCP and UDP traffic, so newer transports such as QUIC cannot slip past unobserved. Run strings over a SealedBrief core.db and you find no readable document text and no file paths — only high-entropy noise.

What does it cost, and what happens after three years?

The free 14-day trial is the full product and needs no account and no card. Every purchase is backed by a 30-day refund, separate from the free trial. Year one includes updates and support in the purchase price, and an annual support fee applies in years two and three of the term.

After the first launch the document work runs offline, because the models ship inside the app and nothing is fetched at runtime. The licence is an Ed25519-signed file that is verified offline, so activation keeps working for the rest of your term even without the vendor. The Personal tier is a 3-year term licence priced at $199, with support in years two and three billed separately. If the term lapses, the vault opens read-only and nothing is deleted.

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This article was drafted with AI assistance.