An information processing apparatus, a software update method, and an image processing apparatus capable of encrypting and decrypting information using values uniquely calculated from booted primary modules or booted backup modules with less effort are disclosed. The information processing apparatus includes primary modules and the same kinds of backup modules, and includes a value storage unit storing values calculated from the modules, an encryption information storage unit storing information unique to the modules, an information decryption unit decrypting the information unique to the modules using the values in the value storage unit, and an encryption information update unit, when the module is updated, encrypting the information unique to the modules based on a value calculated from the each kind of the primary modules or the backup modules after the update.