Where better to store them? Blockchain?
Oh, this fashion.
The blockchain is a protection against fakes.
Assuming that someone will conduct themselves regardless of double transaction.
Thus, you do someone will not be able to cheat.
Will you be someone (an independent organisation/independent person)?
If not - then no blockchain, it does not benefit from buduet.
Otherwise - the usual neradovac server DBMS with synchronous replication, but at least PostgreSQL.
And the rank and file of the signature, even though the RSA algorithm