Cryptanalyses and improvements of two cryptographic key assignment schemes for dynamic access control in a user hierarchy

摘要

Recently, Wu and Chang and Shen and Chen separately proposed a cryptographic key assignment scheme for solving access control problem in a partially ordered user hierarchy. However, this paper will show the security leaks inherent in both schemes based on polynomial interpolations. That is, the users can have access to the information items held by others without following the predefined partially ordered relation. Finally, we proposed two improvements to eliminate such security flaws. [References: 6]