1. A data processing system, comprising: an application processor comprising a memory; a memory device comprising a memory core; and a channel connecting the application processor and the memory device, wherein the application processor is configured to store first data as plaintext data in the memory, encrypt the plaintext data into first encrypted data using a first encryption key and a first initialization vector in response to a write command, and transmit the first encrypted data to the memory device through the channel, the memory device is configured to decrypt the first encrypted data into first decrypted data using a second encryption key and a second initialization vector, and store the first decrypted data in the memory core, the first encryption key and the first initialization vector are stored in the application processor, the second encryption key and the second initialization vector are stored in the memory device, the first encryption key is identical to the second encryption key, and the first initialization vector is identical to the second initialization vector, and the application processor is configured to count a number of issues of the write command and determine whether to update the first initialization vector according to a count result obtained by counting the number of issues of the write command, wherein encrypting the plaintext data into the first encrypted data using the first encryption key and the first initialization vector protects the first encrypted data from an external physical attack while the first encrypted data is transmitted from the application processor to the memory device through the channel.