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I don't how to make a cipher text at all, can you help me?

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    $\begingroup$ $E_k(x) = x$ and $D_k(x) = x$ for all strings $x$ and keys $k$. $\endgroup$
    – fkraiem
    Jun 6, 2016 at 1:19
  • $\begingroup$ @fkraiem I probably shouldn't +1 that, but I couldn't resist. As to the OP's question: you should probably read an introductory book if you're serious about crypto. See this question, for instance. Or pick up one about the history of cryptography, they're always a good read. $\endgroup$ Jun 6, 2016 at 6:09

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I was in your shoes about a year ago. The biggest help to me was Kahn Academy's crypto lessons (https://www.khanacademy.org/computing/computer-science/cryptography). The best thing it did for me was to define what many of the terms were without going too deep into the math. To directly answer your question, the most basic cipher is letter substitution: A = D, B = E... So to create the cipher, add three letters to each plaintext letter. To get the plaintext back, subtract the same number from each letter. Tada! You have a cipher text!

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  • $\begingroup$ That's called a Caesar cipher or shift (or actually rotational) cipher. Or ROT13 if you do shift 13 up. ROT13 however is an (en)coding as the key is already integrated into the name of the algorithm and not a separate input. $\endgroup$
    – Maarten Bodewes
    Jun 6, 2016 at 17:14
  • $\begingroup$ Simple, basic question. Simple basic answer. $\endgroup$ Jun 6, 2016 at 21:18

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