KeepsakeSovereign Sync — your cloud, not ours
One vault on your PC, your phone and your browser — kept in sync through a private app folder in a cloud you already own. We never see a byte of it.
The problem
Sync is why people surrender their documents to a company cloud: keeping devices consistent is genuinely hard, so vendors make their servers the hub and your data the hostage. Stop paying, lose access. Vendor breached, you're in the disclosure letter.
The irony is that you already pay for private storage — Drive, OneDrive, a NAS — that document apps refuse to use.
How Keepsake solves it
☁️Bring your own cloud
Google Drive app-folder, OneDrive approot, any WebDAV server, or a plain folder (NAS, Syncthing, USB). The vault replicates as opaque ciphertext files.
🔀Edits merge, never clobber
Change a tag on your phone and a note on your PC — both survive. Sync is built on an operation log with deterministic merge, not last-writer-wins file copying.
💻Every platform is a peer
Windows, Android and the web app all read and write the same sync layout. Any device can restore the whole vault from the cloud copy.
Under the hood — op-log replication
- Every mutation is an operation in an encrypted, append-only journal; devices exchange operation batches and converge by field-level, order-independent merge with tombstones — proven by randomized three-device torture tests.
- Batches are AEAD-bound to device, sequence and epoch, so a replayed or reordered file is detected instead of silently applied.
- The provider sees only
KPS2ciphertext blobs with meaningless names; OAuth (where used) is scoped to an app-private folder, not your whole drive. - Full-state reconciliation after merge means a brand-new device rebuilds the exact vault, including deletions, from the cloud folder alone.
Trust through specificity: the full crypto design is documented on the security page.
Questions
Does Keepsake get access to my Google Drive or OneDrive?
No. You authorise the app on your device directly with Google/Microsoft, scoped to a hidden app-only folder. The tokens stay on your device, encrypted inside the vault.
Can I sync without any cloud at all?
Yes — point sync at any folder: a NAS share, a Syncthing folder, even a USB stick you carry between machines.
Last verified — by dotnet run --project Keepsake/Keepsake.SmokeTest. Every claim on this site is listed, with its evidence, in the claim ledger.