A memory device includes nonvolatile memory cells, and a secure module to process first data including information about the device stored in the cells to generate a first password key, process second data including information about the device stored in the cells to generate a second password key, generate a public key and a secret key by a public-key cryptography algorithm, using the first password key and the second password key, and provide the first password key, the second password key, the public key, and the secret key to the cells to store the first password key, the second password key, the public key, and the secret key, where the second data is different from the first data, a value of the first password key value and a value of the second password key are prime numbers, and the public key is provided to a host connected to the device.