What you are asking for is finding the Holy Grail: it has never been done successfully. You can hide such a string
a little bit but never - by definition - completely.
A famous example being Borland trying to hide its copyright string, which was actually a decent effort, but also was demonstrated to be futile. (still on delphibasics.info with full explanation)
It only protects against the most naive type of hackers. Anyway, plenty of those Grail examples available. I also tried to do such things 35-40 years ago......
For mathematicians: there is a proof that it can not be done by the late but super famous prof. Marsalia (known for random theory). Have to look up the paper for that, it was written for fun and teaching purpose.
Note there are such naive ways in the strutils unit. May be enough for you? xorencode, xordecode and xorstring
https://www.freepascal.org/docs-html/rtl/strutils/index-5.html Xor crypt is something every programmer has done...or in your case will do...
You can make it a bit more complex with any other two way cipher, but I would not spend too much time on it....