gendhparams.html
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<TITLE>Generating a Parameter Set for the Diffie-Hellman Key Agreement Algorithm
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<B><A HREF="../javax.crypto/pkg.html">javax.crypto</A></B><font color="#666666" SIZE="-2">
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<B><A HREF="../javax.crypto/pkg.html#Key%20Agreement">Key Agreement</A></B><font color="#666666" SIZE="-2">
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<h3>
e470.
Generating a Parameter Set for the Diffie-Hellman Key Agreement Algorithm</h3>
Two parties use a <font color="#0066ff"><i>key agreement protocol</i></font> to generate identical
secret keys for encryption without ever having to transmit the secret
key. The protocol works by both parties agreeing on a set of values
(a prime, a base, and a private value) which are used to generate a
key pair. This example demonstrates how to generate the set of
values.
<P> The two parties then exchange the generated public keys and
then use it to compute the secret encryption key. This is
demonstrated in <a href="../javax.crypto/KeyAgree.html" class="eglink"><font size="-1"><b>e471</b> Generating a Secret Key Using the Diffie-Hellman Key Agreement Algorithm</font></a>.
<pre>
// Returns a comma-separated string of 3 values.
// The first number is the prime modulus P.
// The second number is the base generator G.
// The third number is bit size of the random exponent L.
public static String genDhParams() {
try {
// Create the parameter generator for a 1024-bit DH key pair
AlgorithmParameterGenerator paramGen = AlgorithmParameterGenerator.getInstance("DH");
paramGen.init(<font color="#0066ff"><i>1024</i></font>);
// Generate the parameters
AlgorithmParameters params = paramGen.generateParameters();
DHParameterSpec dhSpec
= (DHParameterSpec)params.getParameterSpec(DHParameterSpec.class);
// Return the three values in a string
return ""+dhSpec.getP()+","+dhSpec.getG()+","+dhSpec.getL();
} catch (NoSuchAlgorithmException e) {
} catch (InvalidParameterSpecException e) {
}
return null;
}
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Related Examples
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e471. <a class="eglink" href="KeyAgree.html?l=rel">
Generating a Secret Key Using the Diffie-Hellman Key Agreement Algorithm
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See also:
<a class="eglink" href="/egs/javax.crypto/pkg.html?l=rel#Encrypting%20and%20Decrypting">
Encrypting and Decrypting
</a>
<a class="eglink" href="/egs/javax.crypto/pkg.html?l=rel#MAC">
MAC
</a>
<a class="eglink" href="/egs/javax.crypto/pkg.html?l=rel#Symmetric%20Keys">
Symmetric Keys
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