Explore a groundbreaking paper on post-quantum cryptography presented at Eurocrypt 2017. Delve into the concept of quantum-secure symmetric key cryptography based on hidden shifts. Examine classical functions, block ciphers, and Simon's algorithm to understand the foundations of this approach. Investigate the Hidden Shift Problem and its implications for cryptographic security. Learn about coset sampling, random self-reducibility, and the decisional version of the problem. Analyze security reductions and consider the potential impact on future cryptographic systems. Gain insights into the challenges and opportunities in developing quantum-resistant encryption methods.