Cryptography Teaching Based on Problem Oriented: Take the Knowledge Point of Designated Verifier Signature as an Example

In traditional digital signature, anyone who knows the public key of the signer can verify the signer which is not suitable for applying in some environments of needing privacy. Designated verifier signature (DVeSi) scheme can solve this problem in where only the designated verifier can verify the validation of a signature. DVeSi's property makes it broadly be applied into many sences. DVeSi also becomes the main content of the cryptography course in many universities. However, DVeSi's complex makes it be hard to master for students. In our cryptography course, we try to adopt the problem oriented teaching method which has some good effect. In this paper, combining our actual teaching experience and problem oriented teaching method, we analyze the security of two DVeSi schemes which were proposed recently and we find that the two schemes exist some drawbacks. We present the knowledge of DVeSi scheme by presenting their drawbacks and demonstrating the forgery attack and delegation attack existing in the two schemes. Finally, we also give some improvement methods to overcome these drawbacks. Our teaching method has achieved good results for students to acquire knowledge, which has the reference value for other educators.