This book deals with the upcoming threat that may be posed by quantum computers on modern-day security standards, particularly those involving symmetric key ciphers. Considering the progress in the field of quantum computing over the past few years, there is an ever-growing need to analyze the ciphers that are being employed in ensuring security. The symmetric key ciphers are generally considered safe against quantum computers, though one must consider the possible impact due to Grover's search algorithm (that reduces the security claim to the square root bound of what is expected against a...