Contemporary cryptocurrencies are based on a decentralized “blockchain” structure and process. For Bitcoin and other cryptocurrencies, the blockchain records the global ledger of all transactions, and hence “where all the coins are”. The consensus process uses cryptography and hashing to keep the blockchain valid without a single central server.
But, our current motto is, “You can put anything in a blockchain.” For example, we have noted ConfessionCoin, which records “secrets” in a blockchain.
This week, we learn of yet another use of a blockchain: a course offered at the University of Nicosia (Cyprus) issues certificates of completion, recorded in the Bitcoin blockchain.
What they did is to publish a hashed checksum of the certificate document (i.e., the SHA of the official PDF document). The official list of hashes is in turn hashed, and this hash is stored in a transaction in the Bitcoin blockchain.
This outer hash is permanently and publicly available, and cannot be altered without detection. To confirm a certificate is valid, you:
- locate a copy of the index list (PDF), and compute the hash.
- extract the hash from the Bitcoin blockchain
- If these hashes agree, you have the valid index.
- compute the has for the certificate to be tested.
- if that has is in the index, it is valid.
QED. (This is actually quite simple, even if it sounds complex.)
OK, this class studies cryptocurrency and blockchain technology, so this is a fun exercise for them. But is this a good use of a blockchain?
First, this illustrates the right approach: in general, the blockchain is most useful for publishing the “root” of various chains of authority.
Second, this process is extremely similar to common practice on the Internet, in which the hash checksum for a file is published alongside the file. If you obtain the checksum from a trusted source, then you can verify a file, which can contain other checksums (i.e., an index). E.g., we could get the checksum from the U. Nicosia, assuming we could trust we have found the real source.
The blockchain replaces the authoritative, trusted service. Also, the blockchain will remain valid even if Nicosia goes off the net or out of business.
However, using the Bitcoin blockchain is questionable. This is essentially “spam”, a parasite on the payment system.
It would be much better to have a separate blockchain for certifications like this.
Or, this might simply use something like NameCoin, which is a blockchain for domain names. Simply add another link to the chain: find University of Nicosia’s hash, use that to look up the index for UN’s courses, and then find the class index, etc.
So.
Full marks for demonstrating the principle.
But I think this should not be done on top of the Bitcoin blockchain.
Robert McGrath's Blog 