Common Sith was a writing system that stemmed from early hieroglyphics utilized by the Sith.
It was developed over the centuries by Sith scribes who wished to create several less complicated scripts from their hieroglyphic predecessor. While some supplemented the hieroglyphic writing to create a style for ecclesiastical uses, others such as the Common Sith script supplanted it in more mundane settings. Following the discovery of King Adas's Sith Empire by the Dark Jedi, the Sith began using Common Sith script not only to write their own language, but also Galactic Basic Standard.
Darth Vader had Common Sith writing on his armor's chest control panel in the final years of his life.
The access code (aleph lamed zayin shin) to bypass the security droid guarding the Imperial Palace's residential wing in 16 ABY was in Common Sith.
The letters on Darth Vader's control box, which became known as Common Sith, are based on Hebrew letters. Many of the letters are modified or flipped upside down on his control box. The letters on the control box are somewhat different between The Empire Strikes Back and Return of the Jedi. The letters can also be seen on a speeder bike prop in the Star Wars: The Magic of Myth exhibition. The real world Hebrew script is an impure abjad.