To go along with the earlier NCA builder by @SimonMKWii, here's his latest release: A NAX0 Encryptor & Decryptor!
If you been using and enjoying @SimonMKWii's NCA Builder release, then you will love playing around with his latest release NAX0-Cryptor.
GITHub Project Page: --> https://github.com/simonmkwii/NAX0-Crypter
NEWS SOURCE: NAX0-Cryptor - Encrypt (and decrypt) SD card NCAs! (via) GBATemp