The first known cryptography is roughly 4,000 years old.
Around 1900 BCE a scribe carved hieroglyphs in the tomb of an Egyptian nobleman named Khnumhotep II.
In a few places he swapped standard symbols for unusual ones. Scholars don't think this was real secret-keeping. More likely it was for dignity, mystery, or to impress educated visitors.
It is the oldest known instance of the technique that would later become cryptography.