In a coding method for the encryption of information worth protecting on a holographic data storage medium, an item of information (I; I1, I2) to be encrypted is converted into a graphic data image (D1, D2), which is in turn converted into a hologram in order to write the holographic data storage medium (4) therewith. The invention provides for the hologram to be changed graphically before the writing of the holographic data storage medium (4). As a result of the manner in which the hologram is changed graphically, encryption which is less susceptible to faults is achieved in a simple way, which presents increased resistance to a parallelized brute force attack.