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title: JSEncrypt

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<h1>JSEncrypt</h1>

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<h3>Introduction</h3>

<p>When browsing the internet looking for a good solution to RSA Javascript encryption, there is a whole slew of libraries that basically take the fantastic work done by Tom Wu @ <a href="http://www-cs-students.stanford.edu/~tjw/jsbn/">http://www-cs-students.stanford.edu/~tjw/jsbn/</a> and then modify that code to do what they want.</p>

<p>What I couldn't find, however, was a simple wrapper around this library that basically uses the library <a href="https://github.com/travist/jsencrypt/pull/6">practically</a> untouched, but adds a wrapper to provide parsing of actual Private and Public key-pairs generated with OpenSSL.</p>

<p>This library is the result of these efforts.</p>

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<p>

<a href="https://github.com/travist/jsencrypt/archive/master.zip" class="btn btn-primary btn-lg active" role="button">Download</a>

<a href="https://github.com/travist/jsencrypt" class="btn btn-primary btn-lg active" role="button">Github Project</a>

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<h3>How to use this library.</h3><hr>

<p>This library should work hand-in-hand with openssl. With that said, here is how to use this library.</p>

<ul>

<li>Within your terminal (Unix based OS) type the following:</li>

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<pre><code>openssl genrsa -out rsa_1024_priv.pem 1024</code></pre>

<ul>

<li>This generates a private key, which you can see by doing the following...</li>

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<pre><code>cat rsa_1024_priv.pem #if you are on mac you can | pbcopy to copy to the clipboard</code></pre>

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<li>You can then copy and paste this in the Private Key section of the <a href="/jsencrypt/demo/">demo page</a>.</li>

<li>Next, you can then get the public key by executing the following command.</li>

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<pre><code>openssl rsa -pubout -in rsa_1024_priv.pem -out rsa_1024_pub.pem</code></pre>

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<li>You can see the public key by typing...</li>

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<pre><code>cat rsa_1024_pub.pem</code></pre>

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<li>Now you can compare with the one generated in the <a href="/jsencrypt/demo/">demo page</a>..</li>

<li>Now you can then convert to and from encrypted text by doing the following in code.</li>

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<pre><code>// Create the encryption object and set the key.

var crypt = new JSEncrypt();

crypt.setKey(__YOUR_OPENSSL_PRIVATE_OR_PUBLIC_KEY__); //You can use also setPrivateKey and setPublicKey, they are both alias to setKey

//Eventhough the methods are called setPublicKey and setPrivateKey, remember

//that they are only alias to setKey, so you can pass them both a private or

//a public openssl key, just remember that setting a public key allows you to only encrypt.

var text = 'test';

// Encrypt the data with the public key.

var enc = crypt.encrypt(text);

// Now decrypt the crypted text with the private key.

var dec = crypt.decrypt(enc);

// Now a simple check to see if the round-trip worked.

if (dec === text){

alert('It works!!!');

} else {

alert('Something went wrong....');

}

</code></pre>

<ul><li>Look at the <a href="example.html">example page</a> to view this example in action.</li></ul>

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<h3>Other Information</h3><hr>

<p>This library heavily utilizes the wonderful work of Tom Wu found at <a href="http://www-cs-students.stanford.edu/~tjw/jsbn/">http://www-cs-students.stanford.edu/~tjw/jsbn/</a>.</p>

<p>This jsbn library was written using the raw variables to perform encryption. This is great for encryption, but most private keys use a Private Key in the PEM format seen below.</p>

<h4>1024 bit RSA Private Key in Base64 Format</h4>

<pre><code>-----BEGIN RSA PRIVATE KEY-----

MIICXgIBAAKBgQDHikastc8+I81zCg/qWW8dMr8mqvXQ3qbPAmu0RjxoZVI47tvs

kYlFAXOf0sPrhO2nUuooJngnHV0639iTTEYG1vckNaW2R6U5QTdQ5Rq5u+uV3pMk

7w7Vs4n3urQ6jnqt2rTXbC1DNa/PFeAZatbf7ffBBy0IGO0zc128IshYcwIDAQAB

AoGBALTNl2JxTvq4SDW/3VH0fZkQXWH1MM10oeMbB2qO5beWb11FGaOO77nGKfWc

bYgfp5Ogrql4yhBvLAXnxH8bcqqwORtFhlyV68U1y4R+8WxDNh0aevxH8hRS/1X5

031DJm1JlU0E+vStiktN0tC3ebH5hE+1OxbIHSZ+WOWLYX7JAkEA5uigRgKp8ScG

auUijvdOLZIhHWq7y5Wz+nOHUuDw8P7wOTKU34QJAoWEe771p9Pf/GTA/kr0BQnP

QvWUDxGzJwJBAN05C6krwPeryFKrKtjOGJIniIoY72wRnoNcdEEs3HDRhf48YWFo

riRbZylzzzNFy/gmzT6XJQTfktGqq+FZD9UCQGIJaGrxHJgfmpDuAhMzGsUsYtTr

iRox0D1Iqa7dhE693t5aBG010OF6MLqdZA1CXrn5SRtuVVaCSLZEL/2J5UcCQQDA

d3MXucNnN4NPuS/L9HMYJWD7lPoosaORcgyK77bSSNgk+u9WSjbH1uYIAIPSffUZ

bti+jc1dUg5wb+aeZlgJAkEAurrpmpqj5vg087ZngKfFGR5rozDiTsK5DceTV97K

a3Y+Nzl+XWTxDBWk4YPh2ZlKv402hZEfWBYxUDn5ZkH/bw==

-----END RSA PRIVATE KEY-----

</code></pre>

<p>This library simply takes keys in the preceding format, and translates it to those variables needed to perform the encryptions used in Tom Wu's library.</p>

<p>Here are some good resources to investigate further.</p>

<ul>

<li><a href="http://etherhack.co.uk/asymmetric/docs/rsa_key_breakdown.html">http://etherhack.co.uk/asymmetric/docs/rsa_key_breakdown.html</a></li>

<li><a href="http://www.di-mgt.com.au/rsa_alg.html">http://www.di-mgt.com.au/rsa_alg.html</a></li>

<li><a href="https://polarssl.org/kb/cryptography/asn1-key-structures-in-der-and-pem">https://polarssl.org/kb/cryptography/asn1-key-structures-in-der-and-pem</a></li>

</ul>

<p>With this information, we can translate a private key format to the variables required with the jsbn library from Tom Wu by using the following mappings.</p>

<pre><code>modulus =&gt; n

public exponent =&gt; e

private exponent =&gt; d

prime1 =&gt; p

prime2 =&gt; q

exponent1 =&gt; dmp1

exponent2 =&gt; dmq1

coefficient =&gt; coeff

</code></pre>

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