onbitcoinstandard

OBS//SIGNER

An amnesic, air-gapped Bitcoin signer for any spare Android phone. No key is ever stored. The app cannot touch a network. QR codes are the only wire.

Launch the signer Download APK

Best setup: install the APK on a dedicated offline Android phone — it declares zero network permissions, so the OS itself enforces the air gap. The web app is the try-it channel: install it, then switch the device to airplane mode.

what it does

Amnesic by designSeeds are entered fresh each session, held in memory only, wiped on exit. A lost or inspected device reveals nothing.

True-entropy seed creationDice rolls (Coldcard/SeedSigner-verifiable), camera noise, gyro shake — or all of them pooled and hashed together.

Signs PSBTs, catches fraudAnimated QR (ur:crypto-psbt) in and out, Sparrow/SeedSigner interoperable. Change outputs are re-derived from your own key — a swapped address is flagged before you can sign.

Backup you can trustSeedQR & CompactSeedQR export, block-by-block transcription with printable card PDFs, scan-back verification, word-quiz backup test.

verify a release — trust math, not us

gpg --import RELEASE-KEY.asc
gpg --verify SHA256SUMS.asc SHA256SUMS
sha256sum -c SHA256SUMS

Release key — Rajesh Medampudi <rajesh@medampudi.com>:
0EAE AFC5 F896 560D 56E6 8E77 3E5A 9FE1 12B0 22E6
Android publisher cert SHA-256 (constant across all releases):
2be74c6154fcb99e60f4a3083665c4287b8234ac40b9f6750e7dd7b1301cda7a