Good news, that Skype is going to work with Signal to encrypt messaging end to end.
The danger of using the same protocol for many applications is the idea of “monoculture” – when all the rice or bananas are the same strain or variety, they can all succumb to a single virus or other infection. If the protocol is found to be vulnerable, all the messaging applications would be broken.
from the article:
Skype finally getting end-to-end encryption
It’ll use the Signal protocol, also used in WhatsApp, Facebook Messenger, and others.
Since its inception, Skype has been notable for its secretive, proprietary algorithm. It’s also long had a complicated relationship with encryption: encryption is used by the Skype protocol, but the service has never been clear exactly how that encryption was implemented or exactly which privacy and security features it offers.
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