HTML <keygen> Tag

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The <keygen> tag is one of the HTML5 elements. It is responsible for generating a pair of keys (public and private), that are used to encrypt and decrypt data sent to the server when an HTML form is submitted. The public key is sent to the server along with the submitted form data, and the private one is stored on the user’s local device.

The tag is also used to create and verify the digital signature.

The <keygen> element allows the user to choose from a range of key size options, and also choose where to generate the key, for example, in a smart card or software and stored on disk. But this is possible only in case if the user’s browser supports cryptographic hardware.

Syntax

The <keygen> tag is placed in the <form> container; the closing tag isn’t required. But in XHTML, the (<keygen>) tag must be closed (<keygen/>).

Example of the HTML <keygen> tag:

<!DOCTYPE html>
<html>
  <head>
    <title>Title of the document</title>
  </head>
  <body>
    <form action="/form/submit" method="get">
      <keygen name="rsaPublicKey" keytype="RSA">
        User’s name:
        <input type="text" name="usr_name">
        <input type="submit">
    </form>
  </body>
</html>

Try it Yourself »

Result

Browser Support

Dropdown Options in Chrome and Opera running Blink: 2048 (High Grade), 1024 (Medium Grade). In the Opera browser with Presto versions providing a dropdown with 1024, 1280, 1536, 1792, 2048, 2304, 2560, 2816, 3072, 3328, 3584, 3840 and 4096 as options.
Dropdown options in Safari 5: 512 (Low Grade), 1024 (Medium Grade), 2048 (High Grade).
Dropdown options in Firefox and Android: Medium Grade, High Grade.
IOS claims to support it, however, creates a non-functioning empty dropdown.

Note that the '<keygen>' tag is deprecated in HTML5 and should not be used. Instead, it is recommended to use other methods of authentication, such as OAuth or OpenID.

Attributes

Attribute	Value	Description
autofocus	autofocus	Defines that during the loading of the page the element must automatically receive a focus. Not supported in IE and Firefox.
challenge	challenge	Defines the call string, that is passed along with the public key. The attribute value is any text string. If the attribute isn’t specified, the default is an empty string.
disabled	disabled	Indicates that the <keygen> element must be disabled.
form	form_id	Indicates the identifier of the form or forms to which the <keygen> element belongs. Not supported in IE.
keytype		Defines the key encryption algorithm.
	rsa	The user can choose between high and medium security (the default value).
	dsa	The user can select the key size.
	ec	The user can choose between high and medium security. Not supported in IE and Safari.
name	name	Defines the name of the <keygen> element.