Paper 2016/1136

Cryptography During the French and American Wars in Vietnam

Phan Duong Hieu and Neal Koblitz


After Vietnam's Declaration of Independence on 2 September 1945, the country had to suffer through two long, brutal wars, first against the French and then against the Americans, before finally in 1975 becoming a unified country free of colonial domination. Our purpose is to examine the role of cryptography in those two wars. Despite the far greater technological resources of their opponents, the communications intelligence specialists of the Viet Minh, the National Liberation Front, and the Democratic Republic of Vietnam had considerable success in both protecting Vietnamese communications and acquiring tactical and strategic secrets from the enemy. Perhaps surprisingly, in both wars there was a balance between the sides. Generally speaking, cryptographic knowledge and protocol design were at a high level at the central commands, but deployment for tactical communications in the field was difficult, and there were many failures on all sides.

Note: This is a much expanded version of an invited talk by the second author at Asiacrypt 2016.

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Publication info
Published elsewhere. Minor revision. to appear in Cryptologia
wars in Vietnamsignals intelligencecommunications security
Contact author(s)
koblitz @ uw edu
2017-02-06: revised
2016-12-08: received
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      author = {Phan Duong Hieu and Neal Koblitz},
      title = {Cryptography During the French and American Wars in Vietnam},
      howpublished = {Cryptology ePrint Archive, Paper 2016/1136},
      year = {2016},
      note = {\url{}},
      url = {}
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