In 1963, he was hired as a
communications officer for the CIA, in the Office of Communications, which began a 26-year career, after which he retired in December 1989. Scheidt spent 12 years posted overseas, including serving in
Vientiane from 1963,
Damascus and
Tel Aviv from 1966 to 1968,
Manila from 1971 to 1973, and
Athens from 1978 to 1980. Most often he used
one-time pad paper systems of encryption. Scheidt is best known for his involvement with
Kryptos, a sculpture in the CIA courtyard which contains one of the world's most
famous unsolved codes.
Kryptos was created by
Washington, D.C., sculptor Jim Sanborn, who was commissioned by the CIA in the 1980s to create art around their new Headquarters building in 1988. After Sanborn decided he wanted to incorporate some encrypted messages in his artwork, he was teamed with Scheidt, who was in the process of retiring and was called by then-director
William H. Webster "The Wizard of Codes". Up until that point, Sanborn had never used encryption or text in his work. Scheidt taught various encryption methods to Sanborn, who chose the exact messages to be encrypted. Of the messages on the sculpture, three have been solved, but the fourth section, 97 or 98 characters at the very bottom, remains uncracked." In 1991, journalist
Bill Gertz referred to Scheidt as the "
Deep Throat of Codes" while describing his clandestine meetings with Sanborn. This nickname was later said to have been applied to Scheidt by Webster ==TecSec==