Stamp and Verify

Stamp a file to prove it existed at a point in time, and check any proof against Ethereum Classic.

Stamp a File

We send one 32-byte hash to the calendar and give you back a .ots proof. Keep the proof next to the file.

Choose FilesOr drop files here. Any size, any number.

Your file never leaves this device. Hashing runs in a Web Worker on your machine. The page sends only sha256(sha256(file) || nonce), where the nonce is 16 random bytes made here, so the calendar never sees the file or its plain hash. Open the network panel of your browser to check.

Verify a Proof

Check a .ots proof against Ethereum Classic from this browser. The check reads the anchor transaction from the ETC nodes below and asks Etchd nothing.

1Proof

Choose the .ots FileOr drop it here. From Stamp or any OpenTimestamps client.

2Original Fileoptional

Choose the Original FileOr drop it here. Hashed here, never sent.

Or paste the original file's SHA-256

Choose a proof to start

Advanced, ETC Nodes

ETC nodes to ask, one per line

Nodes that must agree

One node decides the result. A single node can lie about the chain, so add a second one you trust.

The default is the local devnet node.

From the Command Line

The Etchd CLI does both from a terminal. It hashes on your machine and sends only the digest.

etchd stamp -c https://etchd.app file.pdf
etchd upgrade file.pdf.ots
etchd verify file.pdf.ots