From a very quick cursory search: this is using VB's `Rnd` to generate random "keys," which is a massive warning sign[1]. `Rnd` is not cryptographically secure[2] and you should not use it for anything remotely close to key generation.

Edit: I also can't find any evidence that this tool changes the default block mode for `RijndaelManaged`[3], which is CBC. Without any other mitigations (which I can't find), this makes this tool vulnerable to a chosen ciphertext attack.

[1]: https://github.com/miroslavpejic85/cryptopocket/blob/main/sr...

[2]: https://docs.microsoft.com/en-us/office/vba/language/referen...

[3]: https://docs.microsoft.com/en-us/dotnet/api/system.security....