I suggest that you get this person and his management to sign a legally enforceable agreement that forbids all forms of reverse engineering, and any other means of gaining access to the stuff you want to protect.
Obfuscation cannot protect you against a determined attempt to reverse engineer. It is theoretically and practically impossible.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…