Abstract: In 1984, Shamir introduced the concept of an identity-based cryptosystem. In this system, each user needs to visit a Key Authentication Center (KAC) and identify him self before joining a communication network. Once a user is accepted, the KAC will provide him with a secret key. In this way if a user wants to communicate with others he only needs to know the identity of his communication partner and the public key of the KAC. There is no public file required in this system. However, Shamir did not succeed in constructing an identity based cryptosystem but only in constructing an identity-based signature scheme. Meshram and Agrawal have proposed an id-based cryptosystem based on double discrete logarithm problem which uses the public key cryptosystem based on double discrete logarithm problem. In this study, we propose the modification in an id based cryptosystem based on the double discrete logarithm problem and we consider the security against a conspiracy of some entities in the proposed system and show the possibility of establishing a more secure system.