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Telegram relies on its proprietary custom cryptographic protocol named MTProto. The protocol's second iteration, MTProto 2.0, addresses earlier cryptographic criticisms and improves integrity checks.
Cryptographic Primitives Used in MTProto 2.0
MTProto 2.0 combines strong, standard primitives to safeguard communication:
- 256-bit AES Encryption: Used in Infinite Garble Extension (IGE) mode to encrypt payload data.
- SHA-256 Hashing: Replaced SHA-1 for Message Authentication Code (MAC) generation to prevent collision attacks.
- 2048-bit RSA Encryption: Utilized during the key exchange phase to authenticate servers.
Improvements over MTProto 1.0
MTProto 2.0 mitigated chosen-ciphertext attacks by including random padding bytes inside the encrypted message envelope before calculating the SHA-256 hash digest, providing stronger cryptographic bounds.
