Original sentence: The back of a mezuzah parchment carries an inscription whose meaning is unclear:  This is a   Caesar cipher -  a one letter shift of the third, fourth, and fifth words of the Shema, "Adonai, Eloheinu, Adonai", "The Lord, our God, the Lord".This inscription, probably Kabbalistic in origin, has appeared on mezuzot for centuries
Edited sentence: Also inscribed on the back of the parchment is a mysterious phrase in Hebrew sofer script:  This phrase, seemingly meaningless gibberish, is in fact, a Caesar cipher, a one letter shift of the third, fourth, and fifth words of the Shema itself, "Adonai, Eloheinu, Adonai", "The Lord, our God, the Lord".It's meaning has been shrouded in mystery but it has appeared on mezuzah parchment for a millennium