Abstract: A fully homomorphic encryption and decryption apparatus and method are provided, which provide efficient (in terms of computational speed and resource consumption) encryption and decryption operations in fully homomorphic encryption schemes. The apparatus comprises a control module configured to obtain a secret key (SK) in response to a configuration message and provide the SK to both encryption and decryption modules via an interconnect bus. The encryption module is configured to obtain a public key (PK), encrypt a plaintext into a ciphertext based on the PK and SK, divide the ciphertext into a set of ciphertext slices based on a PK length and an interconnect bus width, and concurrently provide the set of ciphertext slices together with the PK to the decryption module. The decryption module is configured to concatenate the set of ciphertext slices into the ciphertext and decrypt the ciphertext into the plaintext based on the PK and SK.