step 1 · recompute
Every hash, re-derived
Your browser hashes the contents of each record with SHA-256 and confirms it matches the hash on file. Change one character and the hash changes.
Proof you can run yourself
Don’t trust us. Verify us.
Below is a real Watchtower evidence pack: four signed records of configuration changes across three Microsoft 365 tenants. Press verify and your browser recomputes every SHA-256 hash and checks the Ed25519 signature, entirely on your device, with nothing sent anywhere. Then tamper with a record and watch the maths catch it.
blk#1not checked
Northwind Prod2026-06-30T02:14:07Z
Security defaultsoff→enabledinfo
Legacy authenticationallowed→blockedhigh
sha256 29a44d1c3e49b35ed13891aee1b5746c5207115d…
blk#2not checked
Northwind Prod2026-07-01T02:16:44Z
Mailbox auditingoff→onmed
sha256 830b0bf1970517d15c86df87cecf257c3f22527c…
blk#3not checked
Contoso (EU)2026-07-02T02:15:09Z
Guest sharinganyone→existing-guestsmed
Idle session sign-outnever→15 minlow
sha256 1c9a29cbfcb102fd3f8aedef12c646394602667e…
blk#4not checked
Northwind Prod2026-07-03T09:14:31Z
Legacy authenticationblocked→high
sha256 ce4ba02906b02f7816b5458cc717057f4d0001b9…
ed25519 signature over head ce4ba02906b02f7816b5…not checked
Ready. Press "Verify the pack" to check it on your device.
Tip: verify the pack, then tamper with the highlighted value in block #4 and verify again.
What just happened
Three checks. No trust required.
step 2 · the chain
Every record, linked
Each record carries the hash of the one before it. To rewrite history, an attacker would have to re-hash every later record too, not just one.
step 3 · the signature
Signed by Watchtower
The head of the chain is signed with an Ed25519 key. Without the private key a forged chain cannot be re-signed, so tampering is caught. The maths held the trust, not us.
This is what a record actually is.
Every other tool stores its evidence in its own cloud and asks you to trust the dashboard. This pack needed no dashboard, no login, and no trust in us - the one thing a management tool cannot hand you.