A cryptographic key is a bit string used to control cryptographic algorithms, such as those for data encryption and digital signatures. The security of cryptographic operations relies on both key length and the unpredictability, or min-entropy, of the random source that generates the key. Keys derived from provably random sources significantly enhance security, ensuring resistance against both brute-force attacks and future advances in computational power. Real-world security failures have highlighted the risks of low-quality randomness, underscoring the necessity for high-quality keys in cryptographic systems.