Cryptanalysis on "Secure untraceable off-line electronic cash system"

Recently, Baseri et al. proposed a secure untraceable off-line electronic cash system. They claimed that their scheme could achieve security requirements of an e-cash system such as, untraceability, anonymity, unlinkability, double spending checking, un-forgeability, date-attachability, and prevent forging coins. They further prove the un-forgeability security feature by using the hardness of discrete logarithm problems. However, after cryptanalysis, we found that the scheme cannot attain the security feature, untraceability. We, therefore, modify it to comprise this desired requirement, which is very important in an e-cash system.