Key Escrow Scheme With Flexible Features

A key escrow encryption system is an encryption system with a backup decryption capability that allows authorized persons(users,officers of an organization, and government officials),under certain prescribed conditions,to decrypt ciphertext with the help of information supplied by one or more trusted parties who hold special data recovery keys.Key escrow becames one of the most hot issues concered by cryptograpgy field and information security field after"Key escrow"concept was proposed.A key escrow scheme which can set the number of escrow agents and the respective importance of escrow agents arbitrarily and a new dynamic(k,n)threshold scheme based on ElGamal public key cryptosystem and elliptic curve cryptosystem are proposed by this artical.Shemes not only have good security,but they are also flexible and schemes have the following properties:(1)The user's ElGamal(elliptic curve)private key is generated by management authority,so it can prevent subliminal attack;(2)Monitor department can verify correctness of the secret shadow which was given by escrow agent during monitor procedure,it can prevent attacktion and destrution from interior and legitimate escrow agents;(3)The problem of"once monitor,monitor forever"is solved.