Avira uses the 256 Advanced Encryption Standard (AES-256), which is the norm used worldwide to encrypt data. 256 refers to the key size – the larger the size, the more possible key combinations.
It would require tremendous effort to try all possible combination keys: 256-bit encryption offers more combination possibilities than there are stars in the universe (a septillion or 1042 stars), and the time it takes for billions of computers to crack the encryption goes beyond the age of our universe (13.8 billion years).