Encryption and Big Integer Support

Is there any way to get around modern Encryption Systems in Inform?

You mean, implement a modern encryption algorithm in an Inform game?

You could do it; you’d have to write it from scratch. It would be a lot of work. It would be slow, because bignum algorithms rely on heap-allocated memory and Inform’s handling of that stuff is not efficient.

What about TADS?

BigNumber
tads.org/t3doc/doc/sysman/types.htm

But I think is better to ask questions about TADS into the proper (sub)forum (here you miss audience).