HKDF-Based Encryption Method with Very Long Keys for QKD and RKD

Established symmetric encryption schemes rely on short keys, with their length typically ranging between 128 and 256 bits. However, well-known physical key exchange schemes such as QKD (Quantum Key Distribution) and RKD (Radio-signal Key Distribution) generate megabits of new key material on a regular basis (i.e., daily, weekly, or otherwise). This article presents a new encryption scheme, OTPH, which is specifically designed to handle these megabits of regularly generated new key material. In this scheme, the key material is treated as a very long key, and its enormous entropy is fully exploited. OTPH first uses a bit selection procedure that randomly selects bits from the circularly arranged key, thereby extending the key many times over. From this, an HKDF (Hash Key Derivation Function) derives many new keys, and the result is a bit sequence that serves as the key for encryption using an XOR operation. OTPH uses only the XOR operation and hash function, which are also used in QKD and RKD during postprocessing (albeit with a different hash function). An initial cryptanalysis is also performed. OTPH operates in a manner entirely contrary to established methods, requiring a completely new perspective. It will not compete with AES, ChaCha20, etc., but instead be used primarily in the context of QKD and RKD.