A simple keyword cipher in javascript
I’m reading (slowly) the book CODES, CIPHERS, SECRETS AND CRYPTIC COMMUNICATION by Fred B. Wrixon.
The first example of a cipher is a simple letter substitution – the alphabet is basically shifted.
So I’ve written a letter substitution function that requires two letters and the phrase to be encrypted.
var keywordCipher = function(char1, char2, plaintext) { console.log("got ", char1, char2, plaintext); var comp1 = "abcdefghijklmnopqrstuvwxyz"; var diff = comp1.indexOf(char2) - comp1.indexOf(char1); var msg = { value: plaintext, error: 0, message: "diff: " + diff }; var trans = ""; for(var i =0; i < plaintext.length; i++) { var plainChar = plaintext.charAt(i); if(plainChar == " ") { trans = trans.concat(" "); } else { var transCharPos = (comp1.indexOf(plainChar) + diff)%comp1.length; var transChar = comp1.charAt(transCharPos); trans = trans.concat(transChar); } } msg.value = trans; return msg; }
You can see this in action here.
Posted: March 22nd, 2017 | Author: Ralph Canapa | Filed under: Code Reference | No Comments »
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