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I understand the functions of PGP key-pairs as:

  1. Public key is used to encrypt files so only the private key holder can read them
  2. Private key is used to decrypt files that were encrypted using the associated public key
  3. Private key is used to sign files so that it can be verified the file could have only come from the private key holder
  4. Public key is used to verify a file signed with the associated public key

That makes sense to me. In all those cases the private key is unique to only a single entity and the public key can be used by anyone.

This comes into question because in Kleopatra, the File menu options are organized with the following:

  • Decrypt/verify files...
  • Sign/encrypt files...

This confuses me because based on my understanding of the 4 functions above, the two options would be organized with the private key functions together (decrypt/sign) and vice versa for pub key (encrypt/verify).

Am I misunderstanding the relationship between signing/verifying and the parts of the key-pair, or do I just have different intuition about U/I than Kleopatra's designers?

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    You're right about usage of keys but files are a little different; the sender signs (with own private key) and/or encrypts (with receiver's public key), and the receiver decrypts (with own private key) and/or verifies (with sender's public key) – dave_thompson_085 Dec 2 '17 at 2:00
  • Ah, I see how the functions are paired as they are in Kleopatra then: You would decrypt/verify at the same time, or sign/encrypt at the same time, though to do either pair of functions would use both a public & private key. – cr0 Dec 2 '17 at 2:52
  • If you want to write that as an answer I'll accept it. If you or no one else does I'll answer it myself later and wrap this up. Thanks! – cr0 Dec 2 '17 at 2:53
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Decrypt/verify would be used on a received file; use your private key to decrypt, and the sender's public key to verify their signature.

Sign/encrypt would be used when preparing a file to send to someone else, using your private key to sign and their public key to encrypt it.

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