Abstract:
Symmetric key cryptography refers to the encryption methods in which the same key is used by both the sender and the receiver. Cryptanalysis is a process of finding vulnerabilities in cryptographic algorithms in order to distinguish the algorithm, or to retrieve the plaintext from ciphertext without the knowledge of the secret key, or sometimes to recover the secret key also. In this work, in addition to using existing cryptanalysis techniques to analyze some recent ciphers, we also develop novel cryptanalysis techniques. The cryptanalysis techniques that are involved here are based on both classical and quantum computing models. In classical cryptanalysis, first of all, we break the authenticated encryption scheme FlexAEAD by mounting forgery using the devised iterated truncated differentials. Further, we mount key recover attacks on the underlying keyed permutation of FlexAEAD. We develop new techniques of cryptanalysis by augmenting yoyo game with classical, impossible and improbable differentials and its impact is shown by applying it on public permutation AESQ and AES in the known-key setting. Another new technique is developed by embedding a boomerang attack within a yoyo game, which is shown to be effective by breaking the claimed security of AES-like block ciphers. In quantum cryptanalysis, we analyze several symmetric key schemes by using Simon's algorithm or by combining Simon's with Grover's algorithms. We also provide cost estimation for mounting Grover's attack on lightweight block ciphers KATAN and Present. To strengthen the validity of our results, all practical attacks are experimentally verified.
