strypt-core 0.1.0

Photos carry GPS coordinates and camera serial numbers. PDFs carry author names, organisation names, and editing timestamps. Word documents carry all of that plus the editing sessions they were written in, and the photographs pasted into them arrive with their own GPS still attached. None of it is visible in a normal viewer, and all of it survives to publication. strypt finds it and strips it out.

A single self-contained binary. Memory-safe Rust. No network access in any code path.

Status: 0.1.0, the first release. No external audit. Read docs/KNOWN_LIMITATIONS.md before relying on strypt. Phases 0–3 are complete; packaging is Phase 4 (docs/ROADMAP.md).

A synthetic test photo from corpus/; its GPS, serial number and author are invented.

Formats

Photographs inside a document are stripped by the image handlers. Every other format is reported as unsupported and never passed through. What each handler removes, keeps, and refuses: docs/THREAT_MODEL.md §7.

For other formats, use mat2 or ExifTool: both mature, actively maintained, and covering far more formats. Where mat2 is the better tool for a file strypt does support, docs/KNOWN_LIMITATIONS.md says so.

Why trust the output

Evidence, not an audit: each point links to where it is checked.

• It fails closed. A file strypt cannot fully process produces no output, and an unsupported format is reported as unsupported, never passed through.
• It re-reads its own output. Every stripped file is detected and inspected afresh, and discarded (exit 5) if anything the handler recognises survived. That proves consistency, not omniscience (docs/THREAT_MODEL.md §4.8).
• It cannot phone home. CI rejects any dependency that can open a network connection, transitive ones included, and proves that check fails on every push (ADR-0004).
• No unsafe in strypt's own code, enforced by the compiler; dependencies are checked against RustSec advisories on every push and weekly.
• Every parser is fuzzed. 20 of 22 fuzz targets meet the bar of 24 CPU-hours with saturated coverage (ADR-0044); jxl and png do not yet. All 22 run for a minute on every push.
• Every format is compared against mat2 and ExifTool, and each difference is recorded as a bug or a deliberate choice (docs/THREAT_MODEL.md §7).

What strypt will not do

• It does not redact. A PDF with a black box drawn over text still contains that text.
• It does not change what your document says, or anonymise your writing style.
• It does not clean filenames, and budget_final_jsmith_home.pdf identifies you regardless.
• It does not protect against metadata a platform adds after you upload.
• It cannot defeat fingerprinting. Encoder quirks and camera sensor noise can identify a device from pixel data alone, with no metadata present at all.
• No tool can guarantee complete metadata removal from complex formats. strypt will never claim otherwise.

Before you publish

1. Rename the file. strypt keeps the name you gave it, plus .stripped.
2. Look at what is visible: faces, screens, reflections, street signs, and the text itself.
3. Check the stripped copy with strypt show, and read what strip said it kept.
4. Upload only the stripped copy. A platform may store the file you send even when it shows a re-encoded one.

If strypt calls a file clean and it still carries metadata, that is a security vulnerability. Report it privately through SECURITY.md, not in a public issue.

Install

Download the binary for your platform from the latest release, with SHA256SUMS, and check it before running it:

shasum -a 256 -c SHA256SUMS --ignore-missing                  # prints OK for your file
gh attestation verify strypt-0.1.0-<target> -R FadeHack/strypt  # built by this repository's CI
chmod +x strypt-0.1.0-<target>                                 # Linux and macOS

On Windows, compare Get-FileHash strypt-0.1.0-x86_64-pc-windows-msvc.exe in PowerShell with its line in SHA256SUMS.

The binaries are not code-signed (ADR-0051). Windows may show a SmartScreen warning. On macOS, a file downloaded in a browser must be allowed once in System Settings → Privacy & Security; one fetched with curl does not.

With a Rust toolchain, cargo install strypt builds it instead. strypt-cli on crates.io is the same tool under its original name, yanked on 2026-08-23 (ADR-0026); replace it with strypt.

Tested in CI on Linux, macOS and Windows. On Windows, output takes the permissions of the folder it is written to (docs/KNOWN_LIMITATIONS.md).

Usage

strypt show photo.jpg                  # report what metadata is present; changes nothing
strypt strip photo.jpg                 # write a sanitised copy beside the original
strypt strip --output-dir out/ *.pdf   # write copies elsewhere
strypt strip --in-place report.docx    # overwrite the original (opt-in, never the default)
strypt show --json --recursive ./docs  # machine-readable output for scripting

A failure is loud: a file strypt cannot fully process produces no output. Commands and exit codes: INSTRUCTIONS.md.

show exits non-zero when anything is left to deal with, so a publishing script or CI job can refuse to ship metadata:

strypt show --recursive public/images > /dev/null   # 1: metadata found; 4: a file strypt cannot check

Documentation

Licence

Dual-licensed under MIT or Apache-2.0, at your option. Contributions are accepted under the same dual licence, per the Apache-2.0 contribution clause, unless you state otherwise.