 
Documents published by Suprayi, each with a digital fingerprint recorded on a public blockchain, so you can check that a copy you hold is exactly the one we published, and whether it is still the current version.
- Published here. We publish each document on this page with its date and version.
- Fingerprint timestamped. The file’s fingerprint (not the file) is timestamped on a public blockchain through OpenTimestamps, a free public service.
- Check any copy. Choose a PDF below and your own device tells you whether it matches.
Check your copy
Received a Suprayi document from someone else? Check it here before you rely on it.
Nothing is uploaded. Your browser reads the file and computes its fingerprint on your own device.
Certificates and authorisations
IQAir certificate for PT Supratechnic Instrumentasi Indonesia (Indonesia)
CurrentConfirmed on the public blockchain: block 973,625, 29 Oct 2026, 09:54 (Singapore time). View block
Technical details
SHA-256 fingerprintc483476e9cc6f61e11e1226dbec8001fb2f2278e28b5ff2e5f5dd30112bf4431
Download proof (.ots) · Verify on OpenTimestamps
To check independently, download the document and its proof file, open opentimestamps.org and drop both files onto the page.
How this works
What is a fingerprint?
A fingerprint (SHA-256) is a short code calculated from every byte of a file. Change even one character and the fingerprint changes completely, so matching fingerprints mean identical files.
What does the public blockchain timestamp prove?
That a file with this exact fingerprint existed no later than the time of the public blockchain block shown. Nobody, including Suprayi, can backdate or alter that record.
What does it not prove?
It does not vouch for what the document says, and it is not an endorsement by OpenTimestamps, by the public blockchain, or by any organisation named in a document. It only proves that this is the file Suprayi published, unchanged, and when.
Why are some versions marked "Superseded"?
When a document is updated, the old file is removed from this site. Its fingerprint and proof stay listed so that an older copy can still be recognised as genuine but out of date.
How can I check without trusting this page?
Download the document and its .ots proof, then drop both onto opentimestamps.org. It checks the proof against the public blockchain independently of this website.