experiments/matrixcipher.html at master · timeshifter/experiments · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Matrix Cipher</title>
    <link rel="stylesheet" href="reset.css">
    <style>
        body {
            margin:15px;
            font-size:16px;
        }

        div {
            margin:0.5em 0;
        }

        p {
            margin:0.5em 0;
        }

        p.info {
            font-size:0.8em;
            margin-bottom:1.5em;
        }

        p.error {
            color:red;
            display:inline-block;
        }

        label {
            display:inline-block;
            width:80px;
        }

        button {
            font-size:1.0em;
            display:inline-block;
            margin:0.3em 0;
        }

        textarea {
            padding:0.3em;
        }

        input[type="text"] {
            font-family:'Courier New', Courier, monospace;
            width:600px;
            padding:0.3em;
        }
    </style>
</head>
<body>
    <p><label for="txtAlphabet">Alphabet</label></p>
    <textarea name="txtAlphabet" id="txtAlphabet" cols="80" rows="4" spellcheck="false">abcdefghijklmnopqrstuvwxyz
ABCDEFGHIJKLMNOPQRSTUVWXYZ
1234567890
 .,!?</textarea>
    <p class="info">Line breaks are just for grouping; they will not be encoded.</p>
    <div>
        <label for="txtPlaintext">Plaintext:</label><input type="text" name="txtPlaintext" id="txtPlaintext">
    </div>
    <div>
        <button onclick="Encode();">Encode ↓</button> <button onclick="Decode();">↑ Decode</button> <p id="lblError" class="error"></p>
    </div>
    <div>
        <label for="txtCipher">Cipher:</label><input type="text" name="txtCipher" id="txtCipher" spellcheck="false">
    </div>
    <script>

        function Encode() {
            var alph = txtAlphabet.value.replace(/\n/g, '');
            txtCipher.value='';
            lblError.innerHTML='';
            try{
                var cipher = GenerateCipher(txtPlaintext.value, alph);
                txtCipher.value=cipher;
            }
            catch(e) {
                lblError.innerHTML = e;
            }
        }

        function Decode() {
            var alph = txtAlphabet.value.replace(/\n/g, '');
            txtPlaintext.value = '';
            lblError.innerHTML = '';
            try {
                var plaintext = DecodeCipher(txtCipher.value, alph);
                txtPlaintext.value=plaintext;
            }
            catch (e) {
                lblError.innerHTML = e;
            }

        }

        function GenerateCipher(plaintext, alphabet){
            if(alphabet.indexOf(' ')==-1)
                throw 'Alphabet must contain space.'

            if(plaintext.length==0)
                throw 'Message cannot be blank.'


            var chars = plaintext.split('');
            for(c of chars){
                if(alphabet.indexOf(c)==-1){
                    throw `Character in message but not in alphabet: "${c}"`;
                }
            }

            var sidelen = Math.ceil(Math.sqrt(chars.length));

            //make sure plaintext is the correct length
            while(chars.length<(sidelen*sidelen)){
                chars.push(' ');
            }

            //generate the working matrix
            var matrix = [], x=0, y=0, i=0;
            for(var i=0;i<=sidelen;i++){
                matrix.push(new Array(sidelen+1));
            }

            //put the plaintext character codes as defined by the alphabet into the array
            var idx=0;
            for(y=1;y<=sidelen;y++){
                for(x=1;x<=sidelen;x++){

                    //matrix[y][x]=1;
                    matrix[y][x]=alphabet.indexOf(chars[idx]);

                    //matrix[y][x]=chars[idx];
                    idx++;
                }
            }

            //generate random numbers along the top and left edges
            for(x = 0;x<=sidelen;x++){
                matrix[0][x]=Math.floor(Math.random()*alphabet.length);
                //matrix[0][x]=2;
            }
            for(y=1;y<=sidelen;y++){
                matrix[y][0]= Math.floor(Math.random() * alphabet.length);
                //matrix[y][0]=3;
            }

            //add the header rows and columns down and across
            for(x=0;x<=sidelen;x++){
                for(y=1;y<=sidelen;y++){
                    matrix[y][x]+=matrix[0][x];
                }
            }
            for(y=0;y<=sidelen;y++){
                for(x=1;x<=sidelen;x++){
                    matrix[y][x] += matrix[y][0];
                }
            }

            //unroll and pass through alphabet again
            var cipher='';
            for(y=0;y<=sidelen;y++){
                for(x=0;x<=sidelen;x++){
                    var t = matrix[y][x];
                    while(t>=alphabet.length){
                        t-=alphabet.length;
                    }
                    cipher += alphabet.charAt(t);
                }
            }

            return cipher;
        }

        function DecodeCipher(ciphertext, alphabet) {
            if (alphabet.indexOf(' ') == -1)
                throw 'Alphabet must contain space.'


            var chars = ciphertext.split('');
            if(Math.sqrt(chars.length)!=Math.floor(Math.sqrt(chars.length)) || chars.length==0)
                throw 'Invalid ciphertext length.';

            for(c of chars){
                if(alphabet.indexOf(c)==-1){
                    throw `Character in cipher but not in alphabet: "${c}"`;
                }
            }

            var sidelen = Math.sqrt(chars.length)-1;

            //generate the working matrix
            var matrix = [], x = 0, y = 0, i = 0;
            for (var i = 0; i <= sidelen; i++) {
                matrix.push(new Array(sidelen + 1));
            }

            var idx=0;
            for(y=0;y<=sidelen;y++){
                for(x=0;x<=sidelen;x++){
                    matrix[y][x] = alphabet.indexOf(chars[idx]);
                    idx++;
                }
            }

            //de-add
            for(x=0;x<=sidelen;x++){
                for(y=1;y<=sidelen;y++){
                    matrix[y][x]-=matrix[0][x];
                }
            }
            for(y=0;y<=sidelen;y++){
                for(x=1;x<=sidelen;x++){
                    matrix[y][x]-=matrix[y][0];
                }
            }

            //unroll and decode using the alphabet
            var plaintext='';
            for (y = 1; y <= sidelen; y++) {
                for (x = 1; x <= sidelen; x++) {
                    var t = matrix[y][x];
                    while(t>=alphabet.length){
                        t-=alphabet.length;
                    }

                    while(t<0){
                        t+=alphabet.length;
                    }
                    plaintext+=alphabet.charAt(t);

                }
            }

            return plaintext;
        }


    </script>
</body>
</html>