An encryption device includes a counter, an encryption/decryption unit, and a timer. The counter is configured to generate a first timestamp for a first time. The encryption/decryption unit is configured to concatenate security data and the first timestamp, encrypt the concatenated data into encryption data, transmit the encryption data to a memory device, and decrypt read data transmitted from the memory device into decryption data. The timer is configured to inform the counter and the encryption/decryption unit that a time elapses from the first time to a second time such that the counter generates a second timestamp for the second time and the encryption/decryption unit decrypts the read data into the decryption data. Checking logic implemented by the encryption device is configured to check whether a decryption timestamp of the decryption data is identical to the first timestamp.