Verify calls from family, colleagues, sources against deepfake impersonation.
About this app
When someone who sounds like your mother calls in a panic asking for bail money, Signet lets you verify it's actually her.
Each paired contact generates a rotating 4-word phrase that only the real person's phone can produce. You ask her to read her phrase aloud; you type what you hear. Green banner: verified. Red banner: something's wrong — hang up and call her back on a number you already trust.
Signet works over any channel. Voice calls, video calls, text, email, in person. The only requirement is that the two of you paired once, in person or over a trusted channel, before the crisis.
Built for a world where AI voice cloning is commodity. Defends against:
* Real-time voice and video deepfakes * Pre-recorded deepfake voicemails * Vishing using scraped biographical knowledge * Compromised messaging accounts where the attacker has chat history but not the paired device * SIM swaps * Reflection attacks: the rotating code is direction-aware, so an attacker echoing your own phrase back at you fails
Core properties:
* No server. No cloud. No account. No INTERNET permission. * No telemetry. No analytics. No ads. * Hardware-backed secrets via Android Keystore, StrongBox when available. * Offline-first; airplane mode does not affect any flow. * RFC-validated crypto (X25519, HKDF-SHA-256, AES-256-GCM, BIP-39). * Open source, AGPL-3.0.
v0.3 includes in-person pairing, long-distance pairing, lost-phone recovery via paper or file, multi-relationship storage, in-person rekey, bulk backup (every paired relationship in one encrypted file with a single 8-word unlock), a printable challenge-response grid for when the other side can't reach their phone, liveness prompts for video calls, and screenshot blocking on sensitive screens.
Not included: duress codes (gated on an abuse-analysis pass), account recovery (there is no account), cloud backup (out of scope forever).
Licensed under AGPL-3.0-only, by digital-grease.
What's New in v0.3.6
Imported from the F-Droid repository index.
- v0.3.6
- New: Opt-in Debug Logging (Settings). Off by default. If you hit a
- bug, turn it on, reproduce it, then Export to send us a diagnostic
- log. Secrets are removed and your contacts' names become anonymous
- tags like before anything leaves your phone. It auto-erases
- after 24 hours, and a banner shows whenever it's recording.
Version history
Jun 14, 2026 · 25.1 MB · Android API 28–36 · code 300063
Imported from the F-Droid repository index.
- v0.3.6
- New: Opt-in Debug Logging (Settings). Off by default. If you hit a
- bug, turn it on, reproduce it, then Export to send us a diagnostic
- log. Secrets are removed and your contacts' names become anonymous
- tags like before anything leaves your phone. It auto-erases
- after 24 hours, and a banner shows whenever it's recording.
SHA-256 defc53fbf543606637a359b46e005f0106a8ae8ffc236e79375b1009088f4107
Jun 14, 2026 · 23.6 MB · Android API 28–36 · code 300062
Imported from the F-Droid repository index.
- v0.3.6
- New: Opt-in Debug Logging (Settings). Off by default. If you hit a
- bug, turn it on, reproduce it, then Export to send us a diagnostic
- log. Secrets are removed and your contacts' names become anonymous
- tags like before anything leaves your phone. It auto-erases
- after 24 hours, and a banner shows whenever it's recording.
SHA-256 e618885926f0a897611d88bb7910178ff92e4e251f4b9703af2c18f1a9909ead
Jun 14, 2026 · 21 MB · Android API 28–36 · code 300061
Imported from the F-Droid repository index.
- v0.3.6
- New: Opt-in Debug Logging (Settings). Off by default. If you hit a
- bug, turn it on, reproduce it, then Export to send us a diagnostic
- log. Secrets are removed and your contacts' names become anonymous
- tags like before anything leaves your phone. It auto-erases
- after 24 hours, and a banner shows whenever it's recording.
SHA-256 e4b54732b35deac092b773a2ef1ac2d85a0d445359f23b4db721a1f79e7c8b12
Will it run on your device?
74%
- Targets newer Android builds, so legacy devices may be excluded.
- Multiple CPU architectures are covered.
- Aligned with the latest Android target SDK expectations.
Installation Guide
Open Settings on your Android device
Go to Security → Unknown sources (or Install unknown apps)
Enable "Allow from this source" for your browser or file manager
Open the downloaded APK file from your Downloads folder
Tap "Install" and wait for installation to complete
Launch the app from your home screen
Make sure to re-enable Unknown Sources restrictions after installation for security.
How to install this safely
How to verify the file you downloaded
Before you install anything, confirm the file is the one described here. On a computer, run shasum -a 256 your-download.apk (macOS or Linux) or certutil -hashfile your-download.apk SHA256 (Windows), then compare the output character-for-character with the SHA-256 on this page. If a single character differs, the file is not the build we recorded — delete it.
What the signing certificate proves
Every Android app is signed with a private key that only its developer holds. The fingerprint on this page is a hash of the matching public certificate, and it proves continuity rather than identity: it tells you a build came from whoever signed the earlier ones. Android enforces this at install time — if a package claiming to be dev.digitalgrease.signet is signed with a different key, the system will refuse to install it over your existing copy. A fingerprint that changes between releases is worth pausing on, because a repackaged app that has been modified by someone else cannot keep the original signature.
How to roll back to an earlier version
If the current release misbehaves, 0.3.6 is the last build before it. Android will not install an older version code over a newer one, so you must uninstall Signet first — which clears its local data unless you have a backup. Reinstall the older APK only if its signing fingerprint matches the build you already trust, and check the API range: an older release may target an Android version your device has moved past.
Why we list sources instead of hosting everything
The official store channel is almost always the right choice: it updates automatically and carries the publisher's own distribution guarantees. A direct APK is useful when a device has no store access, when a rollout has not reached your region, or when you need a specific version — and only when the publisher has authorized that copy. APKBrowse does not list pirated, cracked, or unauthorized rebuilds of Signet, and a listing is removed when the evidence for it stops holding up.
Get Signet
Every source we list for dev.digitalgrease.signet is legality-reviewed. Pirated or cracked builds are never offered.
Other sources
F-Droid listing
officialF-Droid builds this app from source and signs it. This is its official listing, with older builds and full release notes.
Source code
verified publisherThe upstream repository this build is compiled from.
We check legality and signature continuity, but device behaviour still varies. Install at your own discretion.
App Information
Security Verification
We record provenance; we do not run malware scans. Verify the hash yourself before installing.
SHA-256 Hash
defc53fbf543606637a359b46e005f0106a8ae8ffc236e79375b1009088f4107
Signing certificate
dcf0ee507c8a7d2dbf18a38b8d232f7dc6afeb3f78cea7cdeb91ac6c3b0b1d36
Permissions Required
What each permission lets Signet do. A highlighted one is worth a second look — not necessarily wrong, just worth asking whether this app needs it.
Previous Versions
The signing certificate fingerprint for this release is on record, so a build that does not match it did not come from this publisher.
More Social apps
More from F-Droid
Report a problem with this listing
A listing is only as good as its corrections. If a source is broken, a signature looks wrong, or this app should not be here, tell the moderation team.