I'm not up to date, but didn't Telegram had a bounty for someone who could read a conversation even by knowing the phone numbers involved? If so, why the writer here didn't got the bounty?
https://moxie.org/blog/telegram-crypto-challenge/
https://www.schneier.com/crypto-gram/archives/1998/1215.html...
Because their contest is a dumb gimmick that doesn't encompass chosen-ciphertext attacks.