Certificates for a pioneering course on cryptocurrencies by the University of Nicosia in Cyprus were recorded on the block chain yesterday, allowing anyone to verify their authenticity.
The free online course, titled DFIN-511: Introduction to Digital Currencies, was taught by Antonis Polemitis and Andreas M Antonopoulos.
The duo published a comprehensive explanation of how they designed the certificates to be block chain verifiable. This means that course graduates no longer have to rely on the university to verify that they completed the course successfully.
"Even if the University of Nicosia and its website were to disappear, so long as the validated hash still exists as a public record, people can [...] authenticate any certificate," the course website said.
How it works
Verifying the university's certificates relies on the OP_RETURN field that is contained in each transaction. The field was designed to allow a small amount of extra data to be stored in the block chain, as a first step towards allowing assets like property or documents like contracts to be exchanged using the protocol.
The course instructors created hashes of the PDF versions of each certificate, collated all the certificates into an index document, and then generated a hash of that. This hash was then entered into the OP_RETURN field of an unspendable transaction.
Hashes are unique strings of characters that can be generated by any input, using an algorithm. In this case, the SHA-256 algorithm, which is also used in the bitcoin protocol, was used. Hashes are only one-way, so someone with a particular certificate can replicate a hash using the algorithm, but that hash can't regenerate the certificate.
Hashes of hashes
The instructors have published the hash of the certificate index on the university's website. Anyone who wishes to verify a certificate must first check that he has the correct index document. This is done by checking the OP_RETURN field of the particular transaction sent by the instructors.
Once the index has been verified, then individual certificates can be verified. This is done by creating a SHA-256 hash of a given certificate, and then comparing it against the hashes listed in the authenticated index document.
For the validation process to work, the index document has to be readily available. The course instructors note that students are encouraged to host the index document themselves to reduce reliance on the document located on the university's website.
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