The earliest known use of cryptography is found in non-standard hieroglyphs carved into the wall of a tomb from the Old Kingdom of Egypt circa 1900 BC. These are not thought to be serious attempts at secret communications, however, but rather to have been attempts at mystery, intrigue, or even amusement for literate onlookers.
Some clay tablets from Mesopotamia somewhat later are clearly meant to protect information—one dated near 1500 BC was found to encrypt a craftsman's recipe for pottery glaze, presumably commercially valuable.
I don't trust your source. 1900 BCE is Middle Kingdom, not Old Kingdom.
Also, a lot of those older cryptic hieroglyphs turned out to be in an early Northwestern Semitic language. The idea was apparently that you're going to have spells effective against snakes coming in on ships from Byblos, the spells should invoke the deities they know in the language they know.
