Cerridwyn Llewyellyn <ceridwyn@wolfenet.com> writes:
I need an algorithm/protocol that is capable of encrypting numerous files with separate keys, but there also needs to be a master key that will be able to decrypt all of them. Is there such a system that is relatively secure? I'd prefer the system to be as secure as possible, but in this application, security is secondary to functionality.
You can get the basic functionality you require by using a regular hybrid PKE system (pubkey encrypts symmetric session key) and encrypting the session key with the public key of a "master key" as well. For example, assuming a user A and a master key C you just have the program A uses to encrypt files operate in a manner similar to that used by PGP and other public-key encryption systems [pubkeyA(sessionkey),IDEA(sessionkey,data)] except in addition to the pubkeyA(sessionkey) which encrypts the random key used to encrypt the actual data you add a masterpubkeyC(sessionkey) section to the beginning of the file as well. The resulting data packet is [pubkeyA(sessionkey),masterpubkeyC(sessionkey),IDEA(sessionkey, data)] This system is as secure as the public-key system used for encryption and would actually be fairly easy to hack in to PGP, although the modified PGP messages which contain the master key information would not be usable by regular PGP. jim