Researchers tried several times to have the document declassified, including in 1992, 2004 and 2016. It was initially written to help American NSA agents crack difficult coded messages.
The American Survival Research Foundation offered a reward of $1,000 for cracking one of Thouless’s two codes within three years of his death. It was not claimed.
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Computer capabilities have boosted our decryption technology to great heights. How will the future compare to a past, one in which codes were thought to be a means of communicating after death?