If I'm the second party participating in a three pass protocol (for simplicity, let's say Shamir's Three Pass Protocol) such that:
- Bob sends me a ciphertext
- I encrypt it and send it back
- He removes his encryption and sends it back to me
- I decrypt it fully
Using the information in steps 1 (ciphertext) and 4 (plaintext), how difficult is it for me to determine the key that Bob is using?
I know that this is a somewhat esoteric use-case, but I'm curious.