Cryptocurrencies and credit?

I'm basically new to crypto currencies and the concept of block chains. I've watched a number of videos dealing with block chains and crypto currencies and I get that the main idea appears to be replacing the idea of one government agency or large company providing a necessary element of trust with the idea of that element of trust residing in a peer to peer network. In the case of currencies, the first thing which is prevented is the possibility of criminal replication of value elements.

Nonetheless, real banks and particularly any kind of a national bank has to be able to create credit both for legitimate business purposes and for infrastructure spending on the part of governments. That's the question: assuming for the moment that some enlightened government were to investigate the idea of using a crypto currency for the purposes of a national bank, how would the creation of credit work with such a crypto currency?

Notice that such creation of credit for credit worthy actors does not necessarily even create inflation, particularly where the creation of real physical wealth is involved. Banks generally want us to believe that government spending always creates inflation, but consider the following simpleminded case:

Two shipwreck survivors on an island with five dollars between them left over from the previous life and five clams on the island: a dollar is obviously worth one clam if that's the entire economy of the island. Nonetheless, one of the two finds a machete amongst the remains of their lifeboat, hacks a coconut tree into a crude printing press, kills an octopus, uses the press and the octopus ink to print up five new dollar bills, and pays them to his companion to dig up 15 more clams. There are now $10 bills and circulation and 20 clams on the island, i.e. the guy has just doubled the value of money on the island by printing it. No gold or anything else was required, the only two meaningful things in this picture were productivity and an element of trust.

A question might also arise as to whether some crypto currency might could be used as an international monetary system, at least for commercial banking and physical economics.