The private key is linked to the certificate, so if you use the same certificate at different places, you also need to use the same private key.
If you want each server to have a different key, you need to generate different certificates.
Since the question was asked, the landscape has changed considerably. Today, there are two points that favor a single SSH key for all hosts.
Hardware keys are getting more popular. At least the arguably most popular brand, Yubikey, only supports a single SSH key.
If you are using an LDAP server for authentication, you can add an LDAP schama to store an SSH ...
Actually, the naiive approach of just grabbing a key from a keyserver isn't vulnerable so much to a man-in-the-middle attack as to a poisoning attack.
In a poisoning attack, an attacker provides an alternative piece of information, in this case a public key, and somehow tricks you into using that instead of the real one.
In a man-in-the-middle attack, the ...
You seem to instinctively understand that an out of band trust model is important.
With PKI, your OS/Browser/Institution provides, at install or via MDM/GP, you with a list of "Trusted"(deserved or not) CAs that your system will use to extend into a tree of trusted keys/certs.
With PGP/GPG, the developers don't ask you to implicitly trust any one who they ...
Am I correct that this is the way public keys are distributed usually?
Through a central publicly available server?
Yes you use a public key server.MIT public key server is a popular one for that
To my understanding: in nowadays internet systems to gain the public
key of someone usually you (or the client software) looks for the
public key from a ...
Reasons to use symmetric encryption in your case:
It is way faster then asymmetric encryption
Asymmetric encryption is quite expensive when it comes to computing time.
You already have everything in place to use symmetric encryption.
You are distributing Private Keys anyway so why not just distribute a symmetric key.
Asymmetric encryption is not well ...
Yes, there's a reason; public key encryption is very slow and CPU-intensive, and not at all suitable for encrypting chat data, which may well include images, audio or video as well as text. That's why wherever it's used, it's only used to transmit a shared symmetric encryption key which is then used to encrypt the actual content. But in any case, it's never ...