Suppose Alice has at some point in time produced ciphertext $C$ from message $M$ with key $k$. Suppose Alice has then passed $C$ to Bob, and also made a commitment to her key $k$ (thanks to nightcracker for this addition).
Bob then stored it and passed it to a third party Dave, who also possesses $k$ and decrypts to get $M$, and based on $M$, performs certain operations.
Assume that Dave has no contact with Alice and Bob.
Now Alice is incentivised to lie about the contents of $M$ to Bob.
Suppose at a later time that Alice provides Bob with the message $M$. Is there any sequence of actions that Alice can perform to prove to Bob that $M$ was the message she encrypted to give $C$, without handing over the key $k$?
Is there any connection with this: Zero knowledge password proof?