应该是特定的序列组合。有什么问题吗？

An encryption key is typically a random string of bits generated specifically to scramble and unscramble data. Encryption keys are created with algorithms designed to ensure that each key is unique and unpredictable. The longer the key constructed this way, the harder it is to break the encryption code.

但是产生/接受后是双方agree的”固定"序列组合。