Charles Jastrow Mendelsohn (December 8, 1880 – September 27, 1939) was an American cryptographer and classicist.[1] He was the only child of Rabbi Samuel Mendelsohn and Esther Jastrow.[1] [2] [3]
He was born in Wilmington, North Carolina.[1]
He graduated from the Episcopal Academy, Philadelphia in 1896.[1] He was a Harrison Scholar at the University of Pennsylvania, which he graduated with a Bachelor of Arts in 1900 and a PhD in 1904.[1] He was a member of Phi Beta Kappa.[1] He joined the faculty of College of the City of New York as a tutor in Greek in 1905, becoming an instructor in 1907.[1] He was a professor of ancient languages in 1917.[3]
During World War I he served in the censorship department of the Post Office Department in 1917, dealing with foreign language, postal and newspaper censorship.[1] [3] His work came to the attention of Herbert Yardley and he was recruited into Military Intelligence, section 8 (MI-8).[3] From 1918–19 he was a captain in the Military Intelligence Division of the War Department General Staff.[1]
He led a team dealing with German diplomatic correspondence, breaking at least six diplomatic ciphers.[3] Two messages dealt with German attempts to get support from Mexico.[3]
He received an honorable discharge.[3]
He returned to City College in 1920 as a professor of history.[1] [3] He remained interested in cryptography, writing papers and became interested in the history of the topic, collecting many books on it.[1]
He remained in contact with Herbert Yardley and did part time cryptographic work for the Black Chamber.[3] Together they published the Universal Trade Code, a commercial code.[3] He wrote several works for the Black Chamber, including The Zimmermann Telegram of January 16, 1917, and its Cryptographic Background and Studies in German Diplomatic Codes Employed During the World War.[3]
In 1939, he was recalled to active duty as a result of World War II, but while preparing he contracted meningitis and died of it.[1] [3]
His library, which had been called "probably the most important cryptographic library in America, if not in the world" was bequeathed to the University of Pennsylvania.[1]
He had never married and was survived by his mother.[1] He was buried in the Hebrew Cemetery at Oakdale Cemetery, Wilmington, North Carolina.[1]