Threshold cryptosystem based on multiple cryptographic assumptions

A cryptosystem is a cryptographic scheme that allows a sender to encrypt and send a confidential message or document by using public key, while the receiver can decrypt the encrypted message into its original form by using secret key. Most of the existing cryptosystems are constructed based on single hard number theoretical problems. Furthermore, the concept of group-oriented cryptosystem, known as threshold cryptosystem gives an important role in developing a cryptosystem. In this research, a threshold cryptosystem based on two hard number theoretical problems is presented. The strength of this new threshold cryptosystem is the difficulty to solve both factoring and discrete logarithm problems simultaneously. The security analysis of the scheme shows that it is secure against common security attacks.