Pigpen cipher

from wikipedia:

The pigpen cipher (sometimes called the masonic cipher or Freemason's cipher) is a simple substitution cipher exchanging letters for symbols based on a grid. The use of symbols is no impediment to cryptanalysis however, and cryptanalysis is identical to that of other simple substitution schemes. The example key shows one way the letters can be assigned to the grid.

The scheme was used so often by the Freemasons that it is often called the Freemason's cipher. They began using it in the early 1700s to keep their records private and for correspondence (Kahn, 1967, p.~772; Newton, 1998, p. 113). Due to the simplicity of the cipher, it is still used by schoolchildren today.

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