How do we encrypt a password using another password?

Question

Heys all I've got a nub question, I was wondering

What does it mean to encrypt a password using another password?

For example I want to encrypt a password foo using a password bar, does it mean that I append bar to foo (barfoo in other words) and then do a HASH("barfoo") ?

Or does the article really mean another thing when it says in Scene II:

This ticket contains a version of your username that has been ENCRYPTED USING the MAIL SERVER'S PASSWORD.

Answer 1

This is about real, reversible, symmetric encryption. It is not related to storing a one way hash of a password.

encryptedData = encrypt(data, key)
data = decrypt(encryptedData, key)

The very simple implementation of encrypt("bar", "foo") could return "hpg".

key is the shared secret known to both Charon and the mail service. The linked article calls this key a password.

data of course can be another password. But in this case it is not a password, but some information that Charon wants you to pass on to the mailserver. It is called Ticket. The symmetric encryption ensures that neither you nor anyone else can read it. More needs to be done in order to make it secure, but that is dealt with in later scenes of the play.

By the way Wikipedia has an explanations of Kerberos that is closer to the actual technique. The different way to present it may help to understand it.