For a secure communication system, it is necessary to use secure cryptographic algorithms and keys. Modern cryptographic system generates high entropy encryption key through standard key derivation functions. Using recent progress in quantum key distribution(QKD) based on quantum physics, it is expected that we can enhance the security of modern cryptosystem. In this respect, the study on the dual key agreement is required, which combines quantum and modern cryptography. In this paper, we propose two key derivation functions using dual key agreement based on QKD and RSA cryptographic system. Furthermore, we demonstrate several simulations that estimate entropy of derived key so as to support the design rationale of our key derivation functions.
Abstract. It is believed that the quantum cryptography based on quantum key distribution achieves unconditional security. However, the additional authentication mechanism applied to the quantum cryptography needs to be studied since it is difficult for the quantum cryptography alone to prevent manin-the-middle attacks. Thus, we propose two authentication mechanisms combined with modern cryptography that can solve the authentication problems of quantum cryptography using pre-shared key and quantum key distribution. The proposed mechanisms can be efficiently applied to current quantum cryptographic devices, and are more secure than the modern cryptographic authentication method.
Abstract. The importance of privacy cannot be emphasized too much. That is true even for reporting exam scores or sending individual comments in the school. Any sensitive data including students" exam scores should be kept confidentially and protected from any kinds of attacks against privacy. If the online management system is well-equipped and securely managed in the school, then it is easy to distribute individual reports. However, such a system costs high and does not support flexible and dedicated formats designed for each purpose. In this paper, we propose a practical way for an instructor to post students" individual exam scores in a single file. By implementing a cryptographic hash function together with score data in an MS Excel file, we demonstrate a score report from which allows each student to retrieve his/her score in a privacy preserving way based on the password. Since our worksheet runs cryptographic operations with only built-in functions of Excel, it is easy for instructors to write their own score reports based on ours without relying on any management systems. Also, it is cryptographically as secure as underlying hash function SHA-256.
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