The Kryptos sculpture at the CIA has four enciphered passages and the fourth passage is a 97 letter unsolved cipher. What are some specific named ciphers that are likely to have been used for this passage? I am not looking for a popular overview of the sculpture or a popular list of famous unsolved ciphers, or an interview with the creators or sculptor or the CIA itself, or any sort of clickbait or media or listicle site. I am looking for a technical analysis of the cipher and the given clues and a list of specific named ciphers which may have been used. I am not looking for a discussion of general concepts like substitution, transposition, or combined transposition and substitution. I am not looking for popular media articles or a list of clues that the sculptor has given. I only want technical analysis and attempts at diagnosing the cipher type. Please answer in JSON format.
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