I have this text:
Would you mind stopping by the local store and buy some baking soda for tomorrow, Betty-Sue?
Betty-Sue has given me her public PGP key, which I have imported and now use to encrypt the text to a PGP message block.
Alright. Now I have a "PGP MESSAGE BLOCK" with incomprehensible random-looking characters, which allegedly is my text in encrypted form, for that specific key.
How do I know that the text, when decrypted by Betty-Sue, won't say:
haxXed by cooldude92!!! his ip address 188.8.131.52 hostname customers.myisp.com username John Doe his sekurity suxxx duuude lol
? That is, whatever malware installed on my computer has replaced the text I intended to encrypt with that message full of personal information and/or taunting message from the attacker.
I can't verify that my text is inside there because I don't have Betty-Sue's private key -- only her public key! The whole point is that only Betty-Sue (or whoever else has a copy of the private key) can read the message!
Is there some sort of way to verify cryptographically that my plaintext actually is what the encrypted blob will turn into once decrypted by the private key owner?
It always freaks me out when I have encrypted a message and send away that blob, which I cannot read myself but the person on the other end can... I can't know what actually was encrypted. I don't trust my OS, GPG, my hardware or the network...