Sefer Yitzirah and Zohar 1000-1100 C.E. (Beginnings in 700s? Or Earlier?)

Known to exist and referenced by Isaac the Blind (1160-1236) -- Divine Mystery

Uses Midrash and Gematria

Gematria - A cryptographical system, by which words are assigned numbers based on the letters (numbers) that the words contain (and their order in the word).

Gematria Examples:

The 613 commandments are referred to as TaRYG since: Tov (Ta) = 400 + Resh (R) + 200 + Yod (Y) = 10 + Gimmel (G) = 3, equaling 613.

"I have sojourned (GaRTY) with Laban" (B 32:5), as Rashi (1040-1105) interprets, as
"Even though I sojourned with the evil Laban, I observed the 613 commandments"
Garty - 3 + 200 + 400 + 10 = 613.

No fewer than nine Gematira systems used by Kabbalists.

(Also Notarikon & Temurah - shorthand substitution and letter/word exchange)