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<html>
<head>
<title>JavaScript SHA256 demo</title>
<style>
body {
font-family: Arial, sans-serif;
font-size: 16px;
background-color: #EEE;
color: #222;
margin: 0;
padding: 0;
}
#content {
width: 900px;
margin: auto;
background-color: #E8E8E8;
padding: 1em;
}
h1 {
font-size: 1.4em;
text-align: center;
}
textarea {
width: 100%;
font-size: inherit;
border-radius: 3px;
padding: 0.3em;
}
#button {
width: 100%;
font-size: 0.8em;
line-height: 2em;
}
pre {
margin: 1em;
padding: 1em;
font-size: 12px;
background-color: #FFF;
border: 1px solid #BBB;
border-radius: 5px;
}
</style>
</head>
<body>
<div id="content">
<h1>JavaScript SHA-256 demo</h1>
<p>This is a JavaScript implementation of SHA-256, aiming to be as small as I can make it. The goals are:</p>
<ul>
<li>small size- the minified version is <a href="sha256.min.js">less than a kilobyte</a></li>
<li>readability - the unminified version should be relatively easy to understand
</ul>
<p>It currently only supports ASCII, so if you need to hash Unicode text you'll need to write a decoder.</p>
<script src="sha256.min.js"></script>
<textarea id="input" rows=5>abc</textarea>
<input id="button" type="button" value="calculate" />
<textarea id="output" rows=1 style="text-align: center"></textarea>
<script>
document.getElementById('button').onclick = function () {
document.getElementById('output').value = sha256(document.getElementById('input').value);
};
</script>
<pre><code>var sha256 = function sha256(ascii) {
function rightRotate(value, amount) {
return (value>>>amount) | (value<<(32 - amount));
};
var mathPow = Math.pow;
var maxWord = mathPow(2, 32);
var lengthProperty = 'length'
var i, j; // Used as a counter across the whole file
var result = ''
var words = [];
var asciiBitLength = ascii[lengthProperty]*8;
//* caching results is optional - remove/add slash from front of this line to toggle
// Initial hash value: first 32 bits of the fractional parts of the square roots of the first 8 primes
// (we actually calculate the first 64, but extra values are just ignored)
var hash = sha256.h = sha256.h || [];
// Round constants: first 32 bits of the fractional parts of the cube roots of the first 64 primes
var k = sha256.k = sha256.k || [];
var primeCounter = k[lengthProperty];
/*/
var hash = [], k = [];
var primeCounter = 0;
//*/
var isComposite = {};
for (var candidate = 2; primeCounter < 64; candidate++) {
if (!isComposite[candidate]) {
for (i = 0; i < 313; i += candidate) {
isComposite[i] = candidate;
}
hash[primeCounter] = (mathPow(candidate, .5)*maxWord)|0;
k[primeCounter++] = (mathPow(candidate, 1/3)*maxWord)|0;
}
}
ascii += '\x80' // Append Ƈ' bit (plus zero padding)
while (ascii[lengthProperty]%64 - 56) ascii += '\x00' // More zero padding
for (i = 0; i < ascii[lengthProperty]; i++) {
j = ascii.charCodeAt(i);
if (j>>8) return; // ASCII check: only accept characters in range 0-255
words[i>>2] |= j << ((3 - i)%4)*8;
}
words[words[lengthProperty]] = ((asciiBitLength/maxWord)|0);
words[words[lengthProperty]] = (asciiBitLength)
// process each chunk
for (j = 0; j < words[lengthProperty];) {
var w = words.slice(j, j += 16); // The message is expanded into 64 words as part of the iteration
var oldHash = hash;
// This is now the undefinedworking hash", often labelled as variables a...g
// (we have to truncate as well, otherwise extra entries at the end accumulate
hash = hash.slice(0, 8);
for (i = 0; i < 64; i++) {
var i2 = i + j;
// Expand the message into 64 words
// Used below if
var w15 = w[i - 15], w2 = w[i - 2];
// Iterate
var a = hash[0], e = hash[4];
var temp1 = hash[7]
+ (rightRotate(e, 6) ^ rightRotate(e, 11) ^ rightRotate(e, 25)) // S1
+ ((e&hash[5])^((~e)&hash[6])) // ch
+ k[i]
// Expand the message schedule if needed
+ (w[i] = (i < 16) ? w[i] : (
w[i - 16]
+ (rightRotate(w15, 7) ^ rightRotate(w15, 18) ^ (w15>>>3)) // s0
+ w[i - 7]
+ (rightRotate(w2, 17) ^ rightRotate(w2, 19) ^ (w2>>>10)) // s1
)|0
);
// This is only used once, so *could* be moved below, but it only saves 4 bytes and makes things unreadble
var temp2 = (rightRotate(a, 2) ^ rightRotate(a, 13) ^ rightRotate(a, 22)) // S0
+ ((a&hash[1])^(a&hash[2])^(hash[1]&hash[2])); // maj
hash = [(temp1 + temp2)|0].concat(hash); // We don't bother trimming off the extra ones, they're harmless as long as we're truncating when we do the slice()
hash[4] = (hash[4] + temp1)|0;
}
for (i = 0; i < 8; i++) {
hash[i] = (hash[i] + oldHash[i])|0;
}
}
for (i = 0; i < 8; i++) {
for (j = 3; j + 1; j--) {
var b = (hash[i]>>(j*8))&255;
result += ((b < 16) ? 0 : '') + b.toString(16);
}
}
return result;
};
</code></pre>
</div>
</body>
</html>