What are the "Notary" servers regarding convergence? Who is maintaning the "Notary" servers?
Can someone please explain?
In human words: notary servers are trusted servers that add a "yet another" security level, which actually tries to eliminate MITM (Man-In-The-Middle) attacks.
Notaries act as a mediator to ascertain the validity of a Certificate Authority. Notary servers keep consistency checks on CA root certificates to ensure that a certificate presented by the web-server to the client is consistent with what the Notary server has come to know over an extended period of time.
A "Notary Service" would eliminate the need for operating system vendors to include list of trusted CAs but instead publish list of Notary servers. This option dynamically updates clients as soon as a CA is compromised. The only problem today is that currently, there are not enough "notary servers" available on the internet.
If you're looking for a good example of this type of implementation, you can find it in DNS Root Name Servers which securely maintain Zone records for the internet.
I bet that this practical example is easier to understand than my technical explanation of the definition. ;)
From the Convergence.io details page it can be anyone:
The idea is that you decide which notaries you want to trust.