1. A method comprising: performing operations as follows on a processor of an electronic device: establishing a programmatic association in a one-to-one relationship between mathematical operators and directions of movement that a user can make when selecting number keys among an arrangement of number keys that can be displayed on a display device; receiving a first number from a user selection of a first number key of the arrangement of number keys displayed on the display device; receiving a second number from a user selection of a second number key of the arrangement of number keys; determining a first direction of user movement from the first number key to the second number key; selecting a first mathematical operator among the mathematical operators that is programmatically associated with the first direction; combining the first and second numbers using the first mathematical operator to generate an output number; providing the output number to a secure program to control user access to a protected operation of the secure program.