Described systems and methods allow a host system, such as a computer or a smartphone, to enable a secure environment, which can be used to carry out secure communications with a remote service provider, for applications such as online banking, e-commerce, private messaging, and online gaming, among others. A hypervisor oversees a switch between an insecure environment and the secure environment, in response to a user input, or in response to an event such as receiving a telephone call. Switching from the insecure to the secure environment comprises transitioning the insecure environment to a sleeping state and loading the secure environment from a memory image (snapshot) saved to disk, after checking the integrity of the snapshot. Switching from the secure to the insecure environment comprises transitioning the secure environment into a sleeping state and waking up the insecure environment.