Arthur J. Levenson (February 15, 1914 – August 12, 2007) was a cryptographer, United States Army officer and NSA official who worked on the Japanese J19 and the German Enigma codes.

[1] At the beginning of World War II, the Army called Mr. Levenson to active duty from the Enlisted Reserve Corps.

[5]After completing his service overseas, he remained in the cryptologic business as a civilian with the organizations that eventually evolved into the National Security Agency.

He was a member and subsequently Chief of the Technical Consultants Group, the prestigious cryptanalytic organization where the most difficult problems were attacked.

He took the lead in procuring high-level government support for the project from experts like William O. Baker, head of the Bell Laboratories and longtime member of the President's Foreign Intelligence Advisory Board.

[5] Levenson introduced computer management structure professionals from private industry opening up the organization to innovation from outside of the elite cryptologic workforce.

In this meeting with Whitfield Diffie, Martin Hellman, and Paul Baran, he tried to convince the critics that "56 [bits] is quite adequate", because (among other reasons) brute force attack would never be the weakest link in the security of systems that used DES.

This allowed NSA and other countries to decipher most of the world's financial transactions, until the EFF DES cracker convinced banks to switch to stronger ciphers in 1998.