The present disclosure describes methods of encrypting and decrypting blocks of data stored in computer readable memory for a device using a block cipher with a nonce. In particular, methods of encrypting and decrypting blocks of data where the value of the nonce is based on previous execution instructions of a program executed by the device for a previously executed block are described. Embodiments disclosed include a method of encrypting blocks of data bits stored in computer readable memory for a device using a block cipher with a nonce and a key, the method comprising for each block of data: generating a value of the nonce based on previous execution instructions of a program executed by the device for a previously executed block of data; and encrypting the block of data with the nonce and key using the block cipher.