While modifying your console's software is generally considered legal, using zRIF keys to access copyrighted content you do not own may violate local laws.
mmozeiko/pkg2zip: Decrypts PlayStation Vita pkg file ... - GitHub ps vita zrif key free
Assuming you have found a "free" ZRIF key online (via Reddit, GBAtemp, or Wololo forums), here is how you apply it on your hacked PS Vita (running Enso or HENkaku). or Wololo forums)
A is a string of compressed cryptographic data used to bypass digital rights management (DRM) on the PlayStation Vita ps vita zrif key free