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U.S. officials urge Americans to use encrypted apps amid unprecedented cyberattack
(www.nbcnews.com)
This is a most excellent place for technology news and articles.
Thats not what it means. It means that a third party cannot decrypt it on their servers.
Of course if the "third party" is actually decrypting it on your device, then they can read the messages. I dont know why this is not clear to you.