Combining security solutions in order to achieve stronger (combined) security properties is not straightforward. This paper shows that security-preserving alphabetic language homomorphisms can be used to derive security results for combined security solutions. A relatively simple example of the combination of two different authentication properties (device authentication using a trusted platform module and user authentication using SSL) are integrated. Using security-preserving language homomorphisms it is shown that previously proposed combinations of solutions do not satisfy the desired integrated security properties. Finally, an improved integration of the two solutions is shown to satisfy the desired properties.