[Jami] Usernames

[amuza]

Hello there!

I'm new here and have many questions!

Secure distributed apps normally require the use of unreadable long
strings to identify users. However Jami quickly finds a friend just by
entering their username.

I once heard Ring was using Ethereum for human-readable name
registration and search. Is that correct?

If so, why Ethereum instead of Namecoin?

And, how can it find them so quickly?
That would require every Jami app include the whole blockchain for name
lookups, and I am sure that is not the case. So, is it using some kind
of light blockchain client (kind of Electrum for Bitcoin)?

If that is the case, I guess it is connecting to some trusted real nodes
of the blockchain. How are they chosen? Can they be manually selected?

Cheers!