A student punches a letter into a World War II Enigma encoding machine on display by the National Security Agency at the USA Science & Engineering Festival in Washington, April 6, 2018. The free event continues until Sunday, April 8 until 4 (DoD photo by EJ Hersom)

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Photo credit: © AB Forces News Collection / Alamy / Afripics
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Keywords: dc, engineering, expo, science, sciencey, stem, usa, washington