Our current Cabal directive is Unveil the truth. Since the description ist not really helpful i googled the mentioned Encrytped Data Sermons and found a one year old Thread, where someone asked the the exact same question. Where do these things drop. I tried the every Chaos Legion Vanguard mission and got zero drops. Someone else mentioned Black Legion Vanguard specifically. However, these informations are at least one year old. Did anything change after the 2.0 patch? 

Thanks in advance.