We have a set of public and private keys and certificates on the server. The problem is that while public encryption works fine, the passphrase for the .key file got lost.

So, when trying to execute the following command:

openssl rsa -in the.key


It will obviously ask for the passphrase. Is it possible to get the lost passphrase somehow?

The whole point of having a passphrase is to lock out anyone who does not know it. Allowing it to be recovered would defy the principle and allow hackers who get access to your certificate to recover your keys.

So no, there is no such thing.

What you should do is declare the keys as lost to the issuer so that they revoke your certificate. Then, you have to create a new one from scratch. 
