An encryption key generating engine includes a random number pool, an entangling string generator, and a control circuit. The random number pool stores a plurality of random bits, and values of the plurality of random bits are generated randomly. The entangling string generator provides an entangling string according to an input key. The control circuit is coupled to the random number pool and the entangling string generator. The control circuit retrieves a sequence of random bits from the plurality of random bits stored in the random number pool according to the input key, receive the entangling string from the entangling string generator, and entangle the entangling string with the sequence of random bits to generate a secret key.