Took an English exam with Trinity College recently and was excited to see this on the "certificate" link the give you. 

The thing is, they put an Ethereum logo and hash there, but literally nothing else. I wanted to do some digging to understand how this works.

Overall kind of cool to see, but I wish this wasn't calldata so it could be proven on-chain.

The "blockchain id" is actually a transaction hash on mainnet: https://etherscan.io/tx/0xe1d51281bbbb8d276de787a369c1f0621c999ba39c73112a4b58786f46aee9be It's a 0-value transfer to a 0xdead address, with some binary input data attached.

This took some luck to find, but the whole seems to be a system called https://blockcerts.org/ and their certificate issuance code is open source: https://github.com/blockchain-certificates/cert-issuer 

Basically, they are committing about two merkle hashes per day on-chain to represent batches of certificates, and you are able to proof that your certificate is real via a Merkle proof. 

They don't seem to be exposing the proof data in an obvious way, but to be fair to them, when clicking on "Verify Credential" it appears that they are running some code to do the verification, and you can grab your certificate data and proof from the network request.