http://gbatemp.net/threads/how-to-play-legit-7-x-encrypted-cias-without-gateway-mt-card-4-1-4-5-only.383990/
that's what i followed..it worked flawlessly for me, i was already on 4.2 sysnand to begin with...now i can play my legit MH4 cart without me getting tempted to update my sysnand...and...