Like, say, you are a revolutionary who’s imprisoned, but you are allowed to write letters to your family. How would you covertly send a message to your fellow revolutionaries that only they can decode? (Your family are on your side will pass the letter along)

Obviously, it cannot appear to contain any obvious ciphertext, since the prison guards would just rip up your letter and not send it.

  • dbx12
    9·
    1 day ago

    Your options depend on how much code you can agree on. Ask about imaginary relatives map each name to a meaning, so asking about the health of Aunt Judy could mean that the prison refuses your access to a lawyer and telling you thought about Uncle Sam could mean they keep you in solitary. Or whatever facts you want to communicate. Your revolutionary friends could respond in the same manner. The flaw is in being limited to previously agreed upon code words.

    If you have access to a common book, you can refer to words by page, line and word number. You could embed the numbers as words in a story you are writing to your (imaginary) child. “Behind the seven hills, there were five houses with nine rooms each” can translate to “take the 9th word on page seven, line five”. Obviously you need the exact same copy of the book for this to work, the Bible is quite common for this cipher.

      • dbx12
        3·
        1 day ago

        You usually get the book corresponding to your faith, so that would be an option. Given that the Bible (can’t speak mich about it but way less about the others) has chapters and verses and what not, addressing single words is simple.

        For the “name of relative is the code”, yeah that needs a good memory.