While preparing this Glossary, we tried to find a good definition for that term, but found this to be a muddled area. Experts did not agree. Experts disagree about the basic ideas involved. There also is the idea that compromise of a single key will compromise only the data protected by the single key. In Internet literature, the focus has been on protection against decryption of back traffic in the event of a compromise of secret key material held by one or both parties to a communication.
Experts disagree about forward secrecy in the context of symmetric cryptographic systems.