This article is for Amanda Enterprise (AE)
PFX (Personal Information Exchange) certificates are used for encrypting ZWC backup archives.
There are two kinds of PFX certificates Ã¢â‚¬â€œ signed certificates and self-signed ones.
Signed certificates are issued by a recognized/trusted certificate authority (CA) such as Verisign, Comodo. The list of Certificate Authorities approved by Microsoft is here. You can find an explanation of the differences between signed and self-signed certificates here.
Unless your backup data is to be sent to some external party (which may want to verify the authenticity of data), self-signed certificates can be safely used for encryption with ZWC. You can generate your own self-signed certificate for free using OpenSSL or Abylon SELFcert tool.