How is Telegram encrypted?

Question

Cryptography

Everyone writes about the impossibility of transferring encryption keys, explaining this by the fact that during a dialogue between users, encryption keys are created (public and private), that is, there are thousands of algorithms. Is it true ?? I want to figure out how and what really, if there is someone who understands a little bit - tell me.

Answer 1

1. There are not thousands of algorithms. But the number of options for keys is incalculable.
Telegram uses symmetric 256-bit AES encryption and RSA 2048 encryption. The key exchange is based on the Diffie-Hellman method. Also read the technical FAQ
2. Not all messages and chats are encrypted, but only if you create a secret chat.
3. Read corny Wikipedia - what is a public key.
Briefly.
1. Vasya creates a pair of keys. One is longer (private), the other is shorter (public). One can be encrypted, the other can be decrypted.
2. Vasya gives Anya the public key
3. Anya encrypts the message with them and sends it to Vasya
4. Vasya decrypts it.
At the same time, everyone can intercept and see Vasya's public key, but without the private key they will not be able to decrypt Anya's message.
Anya, in her first message, can transfer her public key so that Vasya can use it to encrypt messages that only Anya can decrypt.
Ideally, a temporary key pair can be generated separately for each chat/session - this is how https works.
PS Useful links:
https://medium.com/@tglive/stop-reading-gizmodo-7f...

Answer 2

https://ru.wikipedia.org/wiki/Cryptosystem_with_open...