Access to the TalkShade system using a username and password allows users to remain independent from the mobile device used to make or receive video communications.

This means that it is possible to place and receive calls from any internet-connected smartphone, even one temporarily borrowed for the occasion.

Outgoing Calls.

Lets assume that the user with alias 1 logs into TalkShade using this device.
They can make calls by entering their own alias and the alias of the person they want to speak with in this case, 2.
If the same user now logs in from a second device, they will be able to make calls normally, while the previous device will become unusable.

Incoming Calls.

The behavior is similar for incoming calls.
The user with alias 2 can be reached anywhere on the internet when the user with alias 1 calls them.
If the user with alias 2 later logs in through a second smartphone, the previous one will no longer receive any calls.

In practice, each login to the TalkShade system activates the current device while disabling any other device previously used.

This design feature of the communication system is called instant portability.

It can be demonstrated that instant portability, both for outgoing and incoming communication, is the necessary condition to ensure user anonymity and to allow any strategy against spyware, even the most advanced.

All communication systems that do not include the feature of instant portability can be attacked in order to compromise the confidentiality of personal communications.