[schlowmo]

If their own FAQ is correct, then definitively NO.

Q: So how do you encrypt data?

We support two layers of secure encryption. Server-client encryption is used in Cloud Chats (private and group chats), Secret Chats use an additional layer of client-client encryption. All data, regardless of type, is encrypted in the same way — be it text, media or files.

Our encryption is based on 256-bit symmetric AES encryption, RSA 2048 encryption, and Diffie–Hellman secure key exchange. You can find more info in the Advanced FAQ.

https://telegram.org/faq#q-so-how-do-you-encrypt-data