Contents: 1 Introduction 1.1 Trust problem 1.2 Ciphertext access control problem 1.3 Efficiency problem in multi-message cryptology 1.4 The challenges from quantum and biological computing 1.5 Organization 2 Proxy re-cryptography 2.1 Introduction 2.2 Proxy re cryptography 2.3 Proxy re-encryption 3 Attribute-based cryptography 3.1 Introduction 3.2 Universal definitions 3.3 Bo…