Validation bug in Extended RSA Cryptosystem (org.jcryptool.visual.extendedrsa)

[tassadarius]

I found out that this plugin has some input validation issues:

Manage keys → create keys

p and q must be at least 13 and prime. By fiddling a little bit around, this check breaks weirdly:

The validation for e just seems to print wrong messages, as you can see in this GIF.
The requirement is, that the common divisor of (p-1)*(q-1) = 1.
I have here the example with 540. Only for 5 the correct message is displayed.

It may be there are further bugs.

Also

The usability is problematic, because it says it must be below phi(N), but you have to calculate phi(N) yourself, if you want to know it.