Kryptographik Lehrbuch der Geheimschreibekunst (Cryptology: Instruction Book on the Art of Secret Writing) is an 1809 book on cryptography written by Johann Ludwig Klüber. In 2011 the National Security Agency included a copy of Kryptographik, used by a German cryptographer during World War II, as part of a 50,000 page release of classified documents.
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