andreyk

The plugin increases security of a site in case it has no SSL certificate, 
useful for owners of small sites who want to secure their passwords and 
other posted data but don’t want to buy SSL certificate for each domain 
and subdomain: it protects from sniffering the most important data such as 
passwords when they are being sent from forms of your site to the server.
When the form served by the plugin is submitted all input data are being 
joined into a string, then this string is being encrypted with AES algorythm 
by disposable key and only encrypred string will be sent.
A browser encrypts the disposable key in javascript by the RSA public key 
and sends it to the server; then the server decrypts it with the RSA private 
key and then use it to decrypt the posted data with AES.
Translations included: Ukrainian, Russian, German and Brazilian Portuguese.
I just adapted usage in WordPress the jCryption jQuery plugin, v. 3.1.0. 
Please check www.jcryption.org to learn how jCryption works.

WP jCryption Security

Prevents forms data against sniffing network traffic through encryption provided by jCryption javascript library.

wp2pgpmail

With PGP Key Generator, your visitors can generate their own private and public PGP keys. It is also possible to use the plugin to encrypt and unencrypt a PGP message.
Check <a href="https://wp2pgpmail.com" rel="nofollow ugc">https://wp2pgpmail.com</a> for more info.
Is it secure ?
<ul>
<li>All code is implememented in readable Javascript.</li>
<li>You can verify the source code.</li>
<li>No binaries are loaded from a server or used embedded.</li>
<li>No hidden transfer of plain text.</li>
</ul>
This plugin is based on the tool developed by <a href="http://ianpurton.com/" rel="nofollow ugc">Ian Purton</a>.

PGP Key Generator

A plugin to generate private and public PGP keys. No need to install any software to encrypt and decrypt PGP messages.

WP jCryption Security vs PGP Key Generator