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<!DOCTYPE html>

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<title>class OpenSSL::PKey::DH - RDoc Documentation</title>

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  <h3>Table of Contents</h3>

  <ul class="link-list" role="directory">
    <li><a href="#class-OpenSSL::PKey::DH-label-Accessor+methods+for+the+Diffie-Hellman+parameters">Accessor methods for the Diffie-Hellman parameters</a>
    <li><a href="#class-OpenSSL::PKey::DH-label-Example+of+a+key+exchange">Example of a key exchange</a>
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  <div id="class-metadata">
    
    
<div id="parent-class-section" class="nav-section">
  <h3>Parent</h3>

  <p class="link"><a href="PKey.html">OpenSSL::PKey::PKey</a>
</div>

    
<div id="includes-section" class="nav-section">
  <h3>Included Modules</h3>

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    <li ><a href="#method-c-generate">::generate</a>
    <li ><a href="#method-c-new">::new</a>
    <li ><a href="#method-i-compute_key">#compute_key</a>
    <li ><a href="#method-i-export">#export</a>
    <li ><a href="#method-i-generate_key-21">#generate_key!</a>
    <li ><a href="#method-i-initialize_copy">#initialize_copy</a>
    <li ><a href="#method-i-params">#params</a>
    <li ><a href="#method-i-params_ok-3F">#params_ok?</a>
    <li ><a href="#method-i-private-3F">#private?</a>
    <li ><a href="#method-i-public-3F">#public?</a>
    <li ><a href="#method-i-public_key">#public_key</a>
    <li ><a href="#method-i-set_key">#set_key</a>
    <li ><a href="#method-i-set_pqg">#set_pqg</a>
    <li ><a href="#method-i-to_der">#to_der</a>
    <li ><a href="#method-i-to_pem">#to_pem</a>
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<main role="main" aria-labelledby="class-OpenSSL::PKey::DH">
  <h1 id="class-OpenSSL::PKey::DH" class="class">
    class OpenSSL::PKey::DH
  </h1>

  <section class="description">
    
<p>An implementation of the Diffie-Hellman key exchange protocol based on discrete logarithms in finite fields, the same basis that <a href="DSA.html"><code>DSA</code></a> is built on.</p>

<h3 id="class-OpenSSL::PKey::DH-label-Accessor+methods+for+the+Diffie-Hellman+parameters">Accessor methods for the Diffie-Hellman parameters<span><a href="#class-OpenSSL::PKey::DH-label-Accessor+methods+for+the+Diffie-Hellman+parameters">&para;</a> <a href="#top">&uarr;</a></span></h3>
<dl class="rdoc-list note-list"><dt>DH#p
<dd>
<p>The prime (an <a href="../BN.html"><code>OpenSSL::BN</code></a>) of the Diffie-Hellman parameters.</p>
</dd><dt>DH#g
<dd>
<p>The generator (an <a href="../BN.html"><code>OpenSSL::BN</code></a>) g of the Diffie-Hellman parameters.</p>
</dd><dt>DH#pub_key
<dd>
<p>The per-session public key (an <a href="../BN.html"><code>OpenSSL::BN</code></a>) matching the private key. This needs to be passed to <a href="DH.html#method-i-compute_key"><code>DH#compute_key</code></a>.</p>
</dd><dt>DH#priv_key
<dd>
<p>The per-session private key, an <a href="../BN.html"><code>OpenSSL::BN</code></a>.</p>
</dd></dl>

<h3 id="class-OpenSSL::PKey::DH-label-Example+of+a+key+exchange">Example of a key exchange<span><a href="#class-OpenSSL::PKey::DH-label-Example+of+a+key+exchange">&para;</a> <a href="#top">&uarr;</a></span></h3>

<pre class="ruby"><span class="ruby-comment"># you may send the parameters (der) and own public key (pub1) publicly</span>
<span class="ruby-comment"># to the participating party</span>
<span class="ruby-identifier">dh1</span> = <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">PKey</span><span class="ruby-operator">::</span><span class="ruby-constant">DH</span>.<span class="ruby-identifier">new</span>(<span class="ruby-value">2048</span>)
<span class="ruby-identifier">der</span> = <span class="ruby-identifier">dh1</span>.<span class="ruby-identifier">to_der</span>
<span class="ruby-identifier">pub1</span> = <span class="ruby-identifier">dh1</span>.<span class="ruby-identifier">pub_key</span>

<span class="ruby-comment"># the other party generates its per-session key pair</span>
<span class="ruby-identifier">dhparams</span> = <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">PKey</span><span class="ruby-operator">::</span><span class="ruby-constant">DH</span>.<span class="ruby-identifier">new</span>(<span class="ruby-identifier">der</span>)
<span class="ruby-identifier">dh2</span> = <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">PKey</span>.<span class="ruby-identifier">generate_key</span>(<span class="ruby-identifier">dhparams</span>)
<span class="ruby-identifier">pub2</span> = <span class="ruby-identifier">dh2</span>.<span class="ruby-identifier">pub_key</span>

<span class="ruby-identifier">symm_key1</span> = <span class="ruby-identifier">dh1</span>.<span class="ruby-identifier">compute_key</span>(<span class="ruby-identifier">pub2</span>)
<span class="ruby-identifier">symm_key2</span> = <span class="ruby-identifier">dh2</span>.<span class="ruby-identifier">compute_key</span>(<span class="ruby-identifier">pub1</span>)
<span class="ruby-identifier">puts</span> <span class="ruby-identifier">symm_key1</span> <span class="ruby-operator">==</span> <span class="ruby-identifier">symm_key2</span> <span class="ruby-comment"># =&gt; true</span>
</pre>

  </section>

  <section id="5Buntitled-5D" class="documentation-section">





     <section id="public-class-5Buntitled-5D-method-details" class="method-section">
       <header>
         <h3>Public Class Methods</h3>
       </header>

      <div id="method-c-generate" class="method-detail ">
        <div class="method-heading">
          <span class="method-callseq">
            generate(size, generator = 2) &rarr; dh
          </span>
          <span class="method-click-advice">click to toggle source</span>
        </div>

        <div class="method-description">
          <p>Creates a new <a href="DH.html"><code>DH</code></a> instance from scratch by generating random parameters and a key pair.</p>

<p>See also <a href="../PKey.html#method-c-generate_parameters"><code>OpenSSL::PKey.generate_parameters</code></a> and <a href="../PKey.html#method-c-generate_key"><code>OpenSSL::PKey.generate_key</code></a>.</p>
<dl class="rdoc-list note-list"><dt><code>size</code>
<dd>
<p>The desired key size in bits.</p>
</dd><dt><code>generator</code>
<dd>
<p>The generator.</p>
</dd></dl>

          <div class="method-source-code" id="generate-source">
            <pre><span class="ruby-comment"># File lib/openssl/pkey.rb, line 118</span>
<span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">generate</span>(<span class="ruby-identifier">size</span>, <span class="ruby-identifier">generator</span> = <span class="ruby-value">2</span>, <span class="ruby-operator">&amp;</span><span class="ruby-identifier">blk</span>)
  <span class="ruby-identifier">dhparams</span> = <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">PKey</span>.<span class="ruby-identifier">generate_parameters</span>(<span class="ruby-string">&quot;DH&quot;</span>, {
    <span class="ruby-string">&quot;dh_paramgen_prime_len&quot;</span> <span class="ruby-operator">=&gt;</span> <span class="ruby-identifier">size</span>,
    <span class="ruby-string">&quot;dh_paramgen_generator&quot;</span> <span class="ruby-operator">=&gt;</span> <span class="ruby-identifier">generator</span>,
  }, <span class="ruby-operator">&amp;</span><span class="ruby-identifier">blk</span>)
  <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">PKey</span>.<span class="ruby-identifier">generate_key</span>(<span class="ruby-identifier">dhparams</span>)
<span class="ruby-keyword">end</span></pre>
          </div>
        </div>


      </div>

      <div id="method-c-new" class="method-detail ">
        <div class="method-heading">
          <span class="method-callseq">
            new &rarr; dh
          </span>
          <span class="method-click-advice">click to toggle source</span>
        </div>
        <div class="method-heading">
          <span class="method-callseq">
            new(string) &rarr; dh
          </span>
        </div>
        <div class="method-heading">
          <span class="method-callseq">
            new(size [, generator]) &rarr; dh
          </span>
        </div>

        <div class="method-description">
          <p>Creates a new instance of <a href="DH.html"><code>OpenSSL::PKey::DH</code></a>.</p>

<p>If called without arguments, an empty instance without any parameter or key components is created. Use <a href="DH.html#method-i-set_pqg"><code>set_pqg</code></a> to manually set the parameters afterwards (and optionally <a href="DH.html#method-i-set_key"><code>set_key</code></a> to set private and public key components).</p>

<p>If a String is given, tries to parse it as a DER- or PEM- encoded parameters. See also <a href="../PKey.html#method-c-read"><code>OpenSSL::PKey.read</code></a> which can parse keys of any kinds.</p>

<p>The <a href="DH.html#method-c-new"><code>DH.new</code></a>(size [, generator]) form is an alias of <a href="DH.html#method-c-generate"><code>DH.generate</code></a>.</p>
<dl class="rdoc-list note-list"><dt><code>string</code>
<dd>
<p>A String that contains the DER or PEM encoded key.</p>
</dd><dt><code>size</code>
<dd>
<p>See <a href="DH.html#method-c-generate"><code>DH.generate</code></a>.</p>
</dd><dt><code>generator</code>
<dd>
<p>See <a href="DH.html#method-c-generate"><code>DH.generate</code></a>.</p>
</dd></dl>

<p>Examples:</p>

<pre class="ruby"><span class="ruby-comment"># Creating an instance from scratch</span>
<span class="ruby-comment"># Note that this is deprecated and will not work on OpenSSL 3.0 or later.</span>
<span class="ruby-identifier">dh</span> = <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">PKey</span><span class="ruby-operator">::</span><span class="ruby-constant">DH</span>.<span class="ruby-identifier">new</span>
<span class="ruby-identifier">dh</span>.<span class="ruby-identifier">set_pqg</span>(<span class="ruby-identifier">bn_p</span>, <span class="ruby-keyword">nil</span>, <span class="ruby-identifier">bn_g</span>)

<span class="ruby-comment"># Generating a parameters and a key pair</span>
<span class="ruby-identifier">dh</span> = <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">PKey</span><span class="ruby-operator">::</span><span class="ruby-constant">DH</span>.<span class="ruby-identifier">new</span>(<span class="ruby-value">2048</span>) <span class="ruby-comment"># An alias of OpenSSL::PKey::DH.generate(2048)</span>

<span class="ruby-comment"># Reading DH parameters</span>
<span class="ruby-identifier">dh_params</span> = <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">PKey</span><span class="ruby-operator">::</span><span class="ruby-constant">DH</span>.<span class="ruby-identifier">new</span>(<span class="ruby-constant">File</span>.<span class="ruby-identifier">read</span>(<span class="ruby-string">&#39;parameters.pem&#39;</span>)) <span class="ruby-comment"># loads parameters only</span>
<span class="ruby-identifier">dh</span> = <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">PKey</span>.<span class="ruby-identifier">generate_key</span>(<span class="ruby-identifier">dh_params</span>) <span class="ruby-comment"># generates a key pair</span>
</pre>

          <div class="method-source-code" id="new-source">
            <pre>static VALUE
ossl_dh_initialize(int argc, VALUE *argv, VALUE self)
{
    EVP_PKEY *pkey;
    int type;
    DH *dh;
    BIO *in = NULL;
    VALUE arg;

    TypedData_Get_Struct(self, EVP_PKEY, &amp;ossl_evp_pkey_type, pkey);
    if (pkey)
        rb_raise(rb_eTypeError, &quot;pkey already initialized&quot;);

    /* The DH.new(size, generator) form is handled by lib/openssl/pkey.rb */
    if (rb_scan_args(argc, argv, &quot;01&quot;, &amp;arg) == 0) {
        dh = DH_new();
        if (!dh)
            ossl_raise(eDHError, &quot;DH_new&quot;);
        goto legacy;
    }

    arg = ossl_to_der_if_possible(arg);
    in = ossl_obj2bio(&amp;arg);

    /*
     * On OpenSSL &lt;= 1.1.1 and current versions of LibreSSL, the generic
     * routine does not support DER-encoded parameters
     */
    dh = d2i_DHparams_bio(in, NULL);
    if (dh)
        goto legacy;
    OSSL_BIO_reset(in);

    pkey = ossl_pkey_read_generic(in, Qnil);
    BIO_free(in);
    if (!pkey)
        ossl_raise(eDHError, &quot;could not parse pkey&quot;);

    type = EVP_PKEY_base_id(pkey);
    if (type != EVP_PKEY_DH) {
        EVP_PKEY_free(pkey);
        rb_raise(eDHError, &quot;incorrect pkey type: %s&quot;, OBJ_nid2sn(type));
    }
    RTYPEDDATA_DATA(self) = pkey;
    return self;

  legacy:
    BIO_free(in);
    pkey = EVP_PKEY_new();
    if (!pkey || EVP_PKEY_assign_DH(pkey, dh) != 1) {
        EVP_PKEY_free(pkey);
        DH_free(dh);
        ossl_raise(eDHError, &quot;EVP_PKEY_assign_DH&quot;);
    }
    RTYPEDDATA_DATA(self) = pkey;
    return self;
}</pre>
          </div>
        </div>


      </div>

    </section>

     <section id="public-instance-5Buntitled-5D-method-details" class="method-section">
       <header>
         <h3>Public Instance Methods</h3>
       </header>

      <div id="method-i-compute_key" class="method-detail ">
        <div class="method-heading">
          <span class="method-callseq">
            compute_key(pub_bn) &rarr; string
          </span>
          <span class="method-click-advice">click to toggle source</span>
        </div>

        <div class="method-description">
          <p>Returns a String containing a shared secret computed from the other party’s public value.</p>

<p>This method is provided for backwards compatibility, and calls <a href="PKey.html#method-i-derive"><code>derive</code></a> internally.</p>

<h3 id="method-i-compute_key-label-Parameters">Parameters<span><a href="#method-i-compute_key-label-Parameters">&para;</a> <a href="#top">&uarr;</a></span></h3>
<ul><li>
<p><em>pub_bn</em> is a <a href="../BN.html"><code>OpenSSL::BN</code></a>, <strong>not</strong> the <a href="DH.html"><code>DH</code></a> instance returned by <a href="DH.html#method-i-public_key"><code>DH#public_key</code></a> as that contains the <a href="DH.html"><code>DH</code></a> parameters only.</p>
</li></ul>

          <div class="method-source-code" id="compute_key-source">
            <pre><span class="ruby-comment"># File lib/openssl/pkey.rb, line 49</span>
<span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">compute_key</span>(<span class="ruby-identifier">pub_bn</span>)
  <span class="ruby-comment"># FIXME: This is constructing an X.509 SubjectPublicKeyInfo and is very</span>
  <span class="ruby-comment"># inefficient</span>
  <span class="ruby-identifier">obj</span> = <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">ASN1</span>.<span class="ruby-constant">Sequence</span>([
    <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">ASN1</span>.<span class="ruby-constant">Sequence</span>([
      <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">ASN1</span>.<span class="ruby-constant">ObjectId</span>(<span class="ruby-string">&quot;dhKeyAgreement&quot;</span>),
      <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">ASN1</span>.<span class="ruby-constant">Sequence</span>([
        <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">ASN1</span>.<span class="ruby-constant">Integer</span>(<span class="ruby-identifier">p</span>),
        <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">ASN1</span>.<span class="ruby-constant">Integer</span>(<span class="ruby-identifier">g</span>),
      ]),
    ]),
    <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">ASN1</span>.<span class="ruby-constant">BitString</span>(<span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">ASN1</span>.<span class="ruby-constant">Integer</span>(<span class="ruby-identifier">pub_bn</span>).<span class="ruby-identifier">to_der</span>),
  ])
  <span class="ruby-identifier">derive</span>(<span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">PKey</span>.<span class="ruby-identifier">read</span>(<span class="ruby-identifier">obj</span>.<span class="ruby-identifier">to_der</span>))
<span class="ruby-keyword">end</span></pre>
          </div>
        </div>


      </div>

      <div id="method-i-export" class="method-detail ">
        <div class="method-heading">
          <span class="method-callseq">
            export &rarr; aString
          </span>
          <span class="method-click-advice">click to toggle source</span>
        </div>

        <div class="method-description">
          <p>Encodes this <a href="DH.html"><code>DH</code></a> to its PEM encoding. Note that any existing per-session public/private keys will <strong>not</strong> get encoded, just the Diffie-Hellman parameters will be encoded.</p>

          <div class="method-source-code" id="export-source">
            <pre>static VALUE
ossl_dh_export(VALUE self)
{
    DH *dh;
    BIO *out;
    VALUE str;

    GetDH(self, dh);
    if (!(out = BIO_new(BIO_s_mem()))) {
        ossl_raise(eDHError, NULL);
    }
    if (!PEM_write_bio_DHparams(out, dh)) {
        BIO_free(out);
        ossl_raise(eDHError, NULL);
    }
    str = ossl_membio2str(out);

    return str;
}</pre>
          </div>
        </div>

        <div class="aliases">
          Also aliased as: <a href="DH.html#method-i-to_pem">to_pem</a>, <a href="DH.html#method-i-to_s">to_s</a>
        </div>

      </div>

      <div id="method-i-generate_key-21" class="method-detail ">
        <div class="method-heading">
          <span class="method-callseq">
            generate_key! &rarr; self
          </span>
          <span class="method-click-advice">click to toggle source</span>
        </div>

        <div class="method-description">
          <p>Generates a private and public key unless a private key already exists. If this <a href="DH.html"><code>DH</code></a> instance was generated from public DH parameters (e.g. by encoding the result of <a href="DH.html#method-i-public_key"><code>DH#public_key</code></a>), then this method needs to be called first in order to generate the per-session keys before performing the actual key exchange.</p>

<p><strong>Deprecated in version 3.0</strong>. This method is incompatible with <a href="../../OpenSSL.html"><code>OpenSSL</code></a> 3.0.0 or later.</p>

<p>See also <a href="../PKey.html#method-c-generate_key"><code>OpenSSL::PKey.generate_key</code></a>.</p>

<p>Example:</p>

<pre class="ruby"><span class="ruby-comment"># DEPRECATED USAGE: This will not work on OpenSSL 3.0 or later</span>
<span class="ruby-identifier">dh0</span> = <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">PKey</span><span class="ruby-operator">::</span><span class="ruby-constant">DH</span>.<span class="ruby-identifier">new</span>(<span class="ruby-value">2048</span>)
<span class="ruby-identifier">dh</span> = <span class="ruby-identifier">dh0</span>.<span class="ruby-identifier">public_key</span> <span class="ruby-comment"># #public_key only copies the DH parameters (contrary to the name)</span>
<span class="ruby-identifier">dh</span>.<span class="ruby-identifier">generate_key!</span>
<span class="ruby-identifier">puts</span> <span class="ruby-identifier">dh</span>.<span class="ruby-identifier">private?</span> <span class="ruby-comment"># =&gt; true</span>
<span class="ruby-identifier">puts</span> <span class="ruby-identifier">dh0</span>.<span class="ruby-identifier">pub_key</span> <span class="ruby-operator">==</span> <span class="ruby-identifier">dh</span>.<span class="ruby-identifier">pub_key</span> <span class="ruby-comment">#=&gt; false</span>

<span class="ruby-comment"># With OpenSSL::PKey.generate_key</span>
<span class="ruby-identifier">dh0</span> = <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">PKey</span><span class="ruby-operator">::</span><span class="ruby-constant">DH</span>.<span class="ruby-identifier">new</span>(<span class="ruby-value">2048</span>)
<span class="ruby-identifier">dh</span> = <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">PKey</span>.<span class="ruby-identifier">generate_key</span>(<span class="ruby-identifier">dh0</span>)
<span class="ruby-identifier">puts</span> <span class="ruby-identifier">dh0</span>.<span class="ruby-identifier">pub_key</span> <span class="ruby-operator">==</span> <span class="ruby-identifier">dh</span>.<span class="ruby-identifier">pub_key</span> <span class="ruby-comment">#=&gt; false</span>
</pre>

          <div class="method-source-code" id="generate_key-21-source">
            <pre><span class="ruby-comment"># File lib/openssl/pkey.rb, line 91</span>
<span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">generate_key!</span>
  <span class="ruby-keyword">if</span> <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">OPENSSL_VERSION_NUMBER</span> <span class="ruby-operator">&gt;=</span> <span class="ruby-value">0x30000000</span>
    <span class="ruby-identifier">raise</span> <span class="ruby-constant">DHError</span>, <span class="ruby-string">&quot;OpenSSL::PKey::DH is immutable on OpenSSL 3.0; &quot;</span> \
    <span class="ruby-string">&quot;use OpenSSL::PKey.generate_key instead&quot;</span>
  <span class="ruby-keyword">end</span>

  <span class="ruby-keyword">unless</span> <span class="ruby-identifier">priv_key</span>
    <span class="ruby-identifier">tmp</span> = <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">PKey</span>.<span class="ruby-identifier">generate_key</span>(<span class="ruby-keyword">self</span>)
    <span class="ruby-identifier">set_key</span>(<span class="ruby-identifier">tmp</span>.<span class="ruby-identifier">pub_key</span>, <span class="ruby-identifier">tmp</span>.<span class="ruby-identifier">priv_key</span>)
  <span class="ruby-keyword">end</span>
  <span class="ruby-keyword">self</span>
<span class="ruby-keyword">end</span></pre>
          </div>
        </div>


      </div>

      <div id="method-i-initialize_copy" class="method-detail ">
        <div class="method-heading">
          <span class="method-name">initialize_copy</span><span
            class="method-args">(p1)</span>
          <span class="method-click-advice">click to toggle source</span>
        </div>

        <div class="method-description">
          

          <div class="method-source-code" id="initialize_copy-source">
            <pre>static VALUE
ossl_dh_initialize_copy(VALUE self, VALUE other)
{
    EVP_PKEY *pkey;
    DH *dh, *dh_other;
    const BIGNUM *pub, *priv;

    TypedData_Get_Struct(self, EVP_PKEY, &amp;ossl_evp_pkey_type, pkey);
    if (pkey)
        rb_raise(rb_eTypeError, &quot;pkey already initialized&quot;);
    GetDH(other, dh_other);

    dh = DHparams_dup(dh_other);
    if (!dh)
        ossl_raise(eDHError, &quot;DHparams_dup&quot;);

    DH_get0_key(dh_other, &amp;pub, &amp;priv);
    if (pub) {
        BIGNUM *pub2 = BN_dup(pub);
        BIGNUM *priv2 = BN_dup(priv);

        if (!pub2 || (priv &amp;&amp; !priv2)) {
            BN_clear_free(pub2);
            BN_clear_free(priv2);
            ossl_raise(eDHError, &quot;BN_dup&quot;);
        }
        DH_set0_key(dh, pub2, priv2);
    }

    pkey = EVP_PKEY_new();
    if (!pkey || EVP_PKEY_assign_DH(pkey, dh) != 1) {
        EVP_PKEY_free(pkey);
        DH_free(dh);
        ossl_raise(eDHError, &quot;EVP_PKEY_assign_DH&quot;);
    }
    RTYPEDDATA_DATA(self) = pkey;
    return self;
}</pre>
          </div>
        </div>


      </div>

      <div id="method-i-params" class="method-detail ">
        <div class="method-heading">
          <span class="method-callseq">
            params &rarr; hash
          </span>
          <span class="method-click-advice">click to toggle source</span>
        </div>

        <div class="method-description">
          <p>Stores all parameters of key to the hash INSECURE: PRIVATE INFORMATIONS CAN LEAK OUT!!! Don’t use :-)) (I’s up to you)</p>

          <div class="method-source-code" id="params-source">
            <pre>static VALUE
ossl_dh_get_params(VALUE self)
{
    DH *dh;
    VALUE hash;
    const BIGNUM *p, *q, *g, *pub_key, *priv_key;

    GetDH(self, dh);
    DH_get0_pqg(dh, &amp;p, &amp;q, &amp;g);
    DH_get0_key(dh, &amp;pub_key, &amp;priv_key);

    hash = rb_hash_new();
    rb_hash_aset(hash, rb_str_new2(&quot;p&quot;), ossl_bn_new(p));
    rb_hash_aset(hash, rb_str_new2(&quot;q&quot;), ossl_bn_new(q));
    rb_hash_aset(hash, rb_str_new2(&quot;g&quot;), ossl_bn_new(g));
    rb_hash_aset(hash, rb_str_new2(&quot;pub_key&quot;), ossl_bn_new(pub_key));
    rb_hash_aset(hash, rb_str_new2(&quot;priv_key&quot;), ossl_bn_new(priv_key));

    return hash;
}</pre>
          </div>
        </div>


      </div>

      <div id="method-i-params_ok-3F" class="method-detail ">
        <div class="method-heading">
          <span class="method-callseq">
            params_ok? &rarr; true | false
          </span>
          <span class="method-click-advice">click to toggle source</span>
        </div>

        <div class="method-description">
          <p>Validates the Diffie-Hellman parameters associated with this instance. It checks whether a safe prime and a suitable generator are used. If this is not the case, <code>false</code> is returned.</p>

<p>See also the man page EVP_PKEY_param_check(3).</p>

          <div class="method-source-code" id="params_ok-3F-source">
            <pre>static VALUE
ossl_dh_check_params(VALUE self)
{
    int ret;
#ifdef HAVE_EVP_PKEY_CHECK
    EVP_PKEY *pkey;
    EVP_PKEY_CTX *pctx;

    GetPKey(self, pkey);
    pctx = EVP_PKEY_CTX_new(pkey, /* engine */NULL);
    if (!pctx)
        ossl_raise(eDHError, &quot;EVP_PKEY_CTX_new&quot;);
    ret = EVP_PKEY_param_check(pctx);
    EVP_PKEY_CTX_free(pctx);
#else
    DH *dh;
    int codes;

    GetDH(self, dh);
    ret = DH_check(dh, &amp;codes) == 1 &amp;&amp; codes == 0;
#endif

    if (ret == 1)
        return Qtrue;
    else {
        /* DH_check_ex() will put error entry on failure */
        ossl_clear_error();
        return Qfalse;
    }
}</pre>
          </div>
        </div>


      </div>

      <div id="method-i-private-3F" class="method-detail ">
        <div class="method-heading">
          <span class="method-callseq">
            private? &rarr; true | false
          </span>
          <span class="method-click-advice">click to toggle source</span>
        </div>

        <div class="method-description">
          <p>Indicates whether this <a href="DH.html"><code>DH</code></a> instance has a private key associated with it or not. The private key may be retrieved with DH#priv_key.</p>

          <div class="method-source-code" id="private-3F-source">
            <pre>static VALUE
ossl_dh_is_private(VALUE self)
{
    DH *dh;
    const BIGNUM *bn;

    GetDH(self, dh);
    DH_get0_key(dh, NULL, &amp;bn);

#if !defined(OPENSSL_NO_ENGINE)
    return (bn || DH_get0_engine(dh)) ? Qtrue : Qfalse;
#else
    return bn ? Qtrue : Qfalse;
#endif
}</pre>
          </div>
        </div>


      </div>

      <div id="method-i-public-3F" class="method-detail ">
        <div class="method-heading">
          <span class="method-callseq">
            public? &rarr; true | false
          </span>
          <span class="method-click-advice">click to toggle source</span>
        </div>

        <div class="method-description">
          <p>Indicates whether this <a href="DH.html"><code>DH</code></a> instance has a public key associated with it or not. The public key may be retrieved with DH#pub_key.</p>

          <div class="method-source-code" id="public-3F-source">
            <pre>static VALUE
ossl_dh_is_public(VALUE self)
{
    DH *dh;
    const BIGNUM *bn;

    GetDH(self, dh);
    DH_get0_key(dh, &amp;bn, NULL);

    return bn ? Qtrue : Qfalse;
}</pre>
          </div>
        </div>


      </div>

      <div id="method-i-public_key" class="method-detail ">
        <div class="method-heading">
          <span class="method-callseq">
            public_key &rarr; dhnew
          </span>
          <span class="method-click-advice">click to toggle source</span>
        </div>

        <div class="method-description">
          <p>Returns a new <a href="DH.html"><code>DH</code></a> instance that carries just the DH parameters.</p>

<p>Contrary to the method name, the returned <a href="DH.html"><code>DH</code></a> object contains only parameters and not the public key.</p>

<p>This method is provided for backwards compatibility. In most cases, there is no need to call this method.</p>

<p>For the purpose of re-generating the key pair while keeping the parameters, check <a href="../PKey.html#method-c-generate_key"><code>OpenSSL::PKey.generate_key</code></a>.</p>

<p>Example:</p>

<pre class="ruby"><span class="ruby-comment"># OpenSSL::PKey::DH.generate by default generates a random key pair</span>
<span class="ruby-identifier">dh1</span> = <span class="ruby-constant">OpenSSL</span><span class="ruby-operator">::</span><span class="ruby-constant">PKey</span><span class="ruby-operator">::</span><span class="ruby-constant">DH</span>.<span class="ruby-identifier">generate</span>(<span class="ruby-value">2048</span>)
<span class="ruby-identifier">p</span> <span class="ruby-identifier">dh1</span>.<span class="ruby-identifier">priv_key</span> <span class="ruby-comment">#=&gt; #&lt;OpenSSL::BN 1288347...&gt;</span>
<span class="ruby-identifier">dhcopy</span> = <span class="ruby-identifier">dh1</span>.<span class="ruby-identifier">public_key</span>
<span class="ruby-identifier">p</span> <span class="ruby-identifier">dhcopy</span>.<span class="ruby-identifier">priv_key</span> <span class="ruby-comment">#=&gt; nil</span>
</pre>

          <div class="method-source-code" id="public_key-source">
            <pre><span class="ruby-comment"># File lib/openssl/pkey.rb, line 33</span>
<span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">public_key</span>
  <span class="ruby-constant">DH</span>.<span class="ruby-identifier">new</span>(<span class="ruby-identifier">to_der</span>)
<span class="ruby-keyword">end</span></pre>
          </div>
        </div>


      </div>

      <div id="method-i-set_key" class="method-detail ">
        <div class="method-heading">
          <span class="method-callseq">
            set_key(pub_key, priv_key) &rarr; self
          </span>
        </div>

        <div class="method-description">
          <p>Sets <em>pub_key</em> and <em>priv_key</em> for the <a href="DH.html"><code>DH</code></a> instance. <em>priv_key</em> may be <code>nil</code>.</p>

        </div>


      </div>

      <div id="method-i-set_pqg" class="method-detail ">
        <div class="method-heading">
          <span class="method-callseq">
            set_pqg(p, q, g) &rarr; self
          </span>
        </div>

        <div class="method-description">
          <p>Sets <em>p</em>, <em>q</em>, <em>g</em> to the <a href="DH.html"><code>DH</code></a> instance.</p>

        </div>


      </div>

      <div id="method-i-to_der" class="method-detail ">
        <div class="method-heading">
          <span class="method-callseq">
            to_der &rarr; aString
          </span>
          <span class="method-click-advice">click to toggle source</span>
        </div>

        <div class="method-description">
          <p>Encodes this <a href="DH.html"><code>DH</code></a> to its DER encoding. Note that any existing per-session public/private keys will <strong>not</strong> get encoded, just the Diffie-Hellman parameters will be encoded.</p>

          <div class="method-source-code" id="to_der-source">
            <pre>static VALUE
ossl_dh_to_der(VALUE self)
{
    DH *dh;
    unsigned char *p;
    long len;
    VALUE str;

    GetDH(self, dh);
    if((len = i2d_DHparams(dh, NULL)) &lt;= 0)
        ossl_raise(eDHError, NULL);
    str = rb_str_new(0, len);
    p = (unsigned char *)RSTRING_PTR(str);
    if(i2d_DHparams(dh, &amp;p) &lt; 0)
        ossl_raise(eDHError, NULL);
    ossl_str_adjust(str, p);

    return str;
}</pre>
          </div>
        </div>


      </div>

      <div id="method-i-to_pem" class="method-detail method-alias">
        <div class="method-heading">
          <span class="method-callseq">
            to_pem &rarr; aString
          </span>
        </div>

        <div class="method-description">
          <p>Encodes this <a href="DH.html"><code>DH</code></a> to its PEM encoding. Note that any existing per-session public/private keys will <strong>not</strong> get encoded, just the Diffie-Hellman parameters will be encoded.</p>

        </div>


        <div class="aliases">
          Alias for: <a href="DH.html#method-i-export">export</a>
        </div>
      </div>

      <div id="method-i-to_s" class="method-detail method-alias">
        <div class="method-heading">
          <span class="method-callseq">
            to_s &rarr; aString
          </span>
        </div>

        <div class="method-description">
          <p>Encodes this <a href="DH.html"><code>DH</code></a> to its PEM encoding. Note that any existing per-session public/private keys will <strong>not</strong> get encoded, just the Diffie-Hellman parameters will be encoded.</p>

        </div>


        <div class="aliases">
          Alias for: <a href="DH.html#method-i-export">export</a>
        </div>
      </div>

    </section>

  </section>
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