Microsoft Teams uses Transport Layer Security (TLS) for encrypted communication. The exact encryption protocol version used for API communication with Teams is TLS 1.2. This ensures that data transmitted between your bot and Teams is encrypted and secure.
The supported cipher suites include those that use AES-256 (in GCM mode) for encryption, which is a strong and secure encryption method.
https://learn.microsoft.com/en-us/microsoftteams/teams-security-guide
https://learn.microsoft.com/en-us/microsoftteams/teams-end-to-end-encryption