Q: What is the origin of the Hebrew letters?
A: The Talmud and Kabbalah teach that the Hebrew letters used today were those used by Moses. The origin of the Hebrew letters is discussed in the Talmud (Sanhedrin 21b-22a) The original letters were the Assyrian script that we presently use to write Torah scrolls and mezuzot. The Torah was originally given in Assyrian script as we have it. This later became a sacred script, holy and "hidden," which was reserved only for the Torah scrolls and use in the Temple. The general script used throughout the First Temple period was the Ivri script. Beginning from the Second Temple period, the Assyrian script was revealed by the masters to the general public, and returned to general use. Nonetheless, there were some remnants of the Ivri script that remained for use in non-religious contexts such as coining, etc. Later generations have developed other scripts in order not to copy the holy script. These include Rashi script and others which are traditionally used for the Hebrew letters.