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<!DOCTYPE html>
<html>
<body>

<h3>A demonstration of how to access a KEYGEN element</h3>

<keygen id="myKeygen" name="security">

<p>Click the button to disable the keygen field.</p>

<button onclick="myFunction()">Try it</button>

<script>
function myFunction() {
    var x = document.getElementById("myKeygen");
    x.disabled = true;
}
</script>

</body>
</html>