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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 55475 (02)
- University: Sharif University of Technology
- Department: Mathematical Sciences
- Advisor(s): Khazaei, Shahram
- Abstract:
- In many sciences, including computer science, generating random numbers have always been an interesting problem.Pseudo-random generators are one of the most important solutions to this problem and one of the primitives, used especially in cryptography and computer science, which have made it easier for us to generate random numbers.The main purpose of these generators is to increase the length of an n-bit string to an l-bit string where l>n.We need an initial value called Seed in this definition. We will present a new and stronger definition in this essay, called the Hinting Pseudorandom Generator, which has different outputs as well. Thus, our input is n bits and our output is n.l bits. We have a hit that is the same as the seed as the name implies, but an attacker is still unable to determine whether the output is a random string or the seed.In this regard, we will examine the methods of constructing a Hinting Pseudorandom Generator, which can be "weak unpredictable homomorphic functions", cryptographic principles, the Φ assumption, and the DDHI assumption.Lastly, we will examine the applications of the Hinting Pseudorandom Generator, including conversion of ciphertext-policy attribute-based encryption, and chosen-ciphertext attack.Furthermore, we compare this security with key-dependent message (KDM) security which requires that ciphertexts preserve secrecy even when the messages are encrypted depending on the secret keys
- Keywords:
- Primitive Model ; Seed ; Weak Unpredictable Homomorphic Function ; Pseudorandom Generator ; Hinting Pseudorandom Generator ; Key Dependent Message