I've looked for the information in the documentation and the forum but didn't find it.
Does anyone know which algoritm is used to encrypt the 3cx backups, when specifying a password ?
That would be my guess too but zip file format supports AES-128, AES-256 and native Zip encryption, which is weak. So there are 3 choices, in addition to a home made / custom algorithm
On the other hand, AES encryption algorithms support any kind of passwords whereas 3CX backup encryption features limits passwords to alpha-numeric only, which weakens it a lot.
That raises a question : is it an algorithm-based or a 3CX implementation-based limitation ?