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155 lines
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 4. Miscellaneous Cryptography</title><link rel="stylesheet" href="docbook.css" type="text/css" /><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /><link rel="start" href="index.html" title="PHP Secure Communications Library" /><link rel="up" href="index.html" title="PHP Secure Communications Library" /><link rel="prev" href="sym_crypt.html" title="Chapter 3. Symmetric-key Cryptography" /><link rel="next" href="net.html" title="Chapter 5. Networking" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 4. Miscellaneous Cryptography</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="sym_crypt.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="net.html">Next</a></td></tr></table><hr /></div><div class="chapter" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title"><a id="misc_crypt"></a>Chapter 4. Miscellaneous Cryptography</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="misc_crypt.html#misc_crypt_hash">4.1. Crypt_Hash</a></span></dt><dd><dl><dt><span class="section"><a href="misc_crypt.html#misc_crypt_hash_supported">4.1.1. Supported Algorithms and Dependencies</a></span></dt><dt><span class="section"><a href="misc_crypt.html#misc_crypt_hash_example">4.1.2. Example</a></span></dt></dl></dd><dt><span class="section"><a href="misc_crypt.html#misc_crypt_rsa">4.2. Crypt_RSA</a></span></dt><dd><dl><dt><span class="section"><a href="misc_crypt.html#misc_crypt_rsa_dependencies">4.2.1. Dependencies</a></span></dt><dt><span class="section"><a href="misc_crypt.html#misc_crypt_rsa_examples">4.2.2. Examples</a></span></dt><dt><span class="section"><a href="misc_crypt.html#misc_crypt_rsa_createkey">4.2.3. createKey()</a></span></dt><dt><span class="section"><a href="misc_crypt.html#misc_crypt_rsa_format">4.2.4. setPrivateKeyFormat(), setPublicKeyFormat(), loadKey() and setPassword()</a></span></dt><dt><span class="section"><a href="misc_crypt.html#misc_crypt_rsa_getpublickey">4.2.5. setPublicKey() and getPublicKey()</a></span></dt><dt><span class="section"><a href="misc_crypt.html#misc_crypt_rsa_encrypt">4.2.6. encrypt(), decrypt() and setEncryptionMode()</a></span></dt><dt><span class="section"><a href="misc_crypt.html#misc_crypt_rsa_sign">4.2.7. sign(), verify(), and setSignatureMode()</a></span></dt><dt><span class="section"><a href="misc_crypt.html#misc_crypt_rsa_params">4.2.8. setHash(), setMGFHash() and setSaltLength()</a></span></dt></dl></dd></dl></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="misc_crypt_hash"></a>4.1. Crypt_Hash</h2></div></div></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="misc_crypt_hash_supported"></a>4.1.1. Supported Algorithms and Dependencies</h3></div></div></div><p>The following algorithms are supported:</p><p>md2, md5, md5-96, sha1, sha1-96, sha256, sha384, and sha512</p><p>
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Crypt_Hash requires, minimally, PHP 4.3.0 (due to its use of
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<a class="ulink" href="http://php.net/function.sha1" target="_top">sha1()</a>). If sha384 or sha512 are being used and
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you're not running PHP 5.1.2 or greater then Math/BigInteger.php is also required.
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</p><p>
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Crypt_Hash uses the hash extension if it's available (> 5.1.2), mhash if it's not, and it's own
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internal implementation if not even mhash is available.
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</p></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="misc_crypt_hash_example"></a>4.1.2. Example</h3></div></div></div><pre class="programlisting"><?php
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include('Crypt/Hash.php');
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$hash = new Crypt_Hash('sha1');
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//$hash->setKey('abcdefg');
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echo bin2hex($hash->hash('abcdefg'));
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?></pre><p>If <code class="code">$hash->setKey()</code> had been called <code class="code">$hash->hash()</code> would have returned an HMAC.</p></div></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="misc_crypt_rsa"></a>4.2. Crypt_RSA</h2></div></div></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="misc_crypt_rsa_dependencies"></a>4.2.1. Dependencies</h3></div></div></div>
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If you're running PHP 5, Crypt_RSA requires Math/BigInteger.php and Crypt/Hash.php. If you're running
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PHP 4, Crypt_RSA also requires PHP/Compat/Function/array_fill.php, PHP/Compat/Function/bcpowmod.php, and
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PHP/Compat/Function/str_split.php
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</div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="misc_crypt_rsa_examples"></a>4.2.2. Examples</h3></div></div></div><p>Here's an example of how to encrypt / decrypt with Crypt_RSA:</p><pre class="programlisting"><?php
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include('Crypt/RSA.php');
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$rsa = new Crypt_RSA();
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extract($rsa->createKey());
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$plaintext = 'terrafrost';
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$rsa->loadKey($privatekey);
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$ciphertext = $rsa->encrypt($plaintext);
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$rsa->loadKey($publickey);
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echo $rsa->decrypt($ciphertext);
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?></pre><p>Here's an example of how to create / verify a signature with Crypt_RSA:</p><pre class="programlisting"><?php
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include('Crypt/RSA.php');
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$rsa = new Crypt_RSA();
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extract($rsa->createKey());
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$plaintext = 'terrafrost';
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$rsa->loadKey($privatekey);
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$signature = $rsa->sign($plaintext);
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$rsa->loadKey($publickey);
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echo $rsa->verify($plaintext, $signature) ? 'verified' : 'unverified';
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></pre></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="misc_crypt_rsa_createkey"></a>4.2.3. createKey()</h3></div></div></div><p>
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<code class="code">createKey()</code> takes three parameters - <code class="code">$bits</code>, <code class="code">$timeout</code>,
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and <code class="code">$primes</code>. <code class="code">$timeout</code> is present since creating a key has the potential to be
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fairly time consuming and will guarantee that <code class="code">createKey()</code> does not run for more than
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<code class="code">$timeout</code> seconds. <code class="code">$primes</code> lets provide pre-computed prime numbers to speed
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things up.
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</p><p>
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<code class="code">extract($rsa->createKey())</code> creates three variables - <code class="code">$publickey</code>,
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<code class="code">$privatekey</code>, and <code class="code">$partialkey</code>. If <code class="code">createKey</code> hit the timeout then
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it'll return all the primes that it had managed to compute so that you might pass them back to
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<code class="code">createKey()</code> on a subsequent call.
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</p><p>
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The exponent can be set by defining <code class="code">CRYPT_RSA_EXPONENT</code> and multi-prime RSA can be utilized
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by adjusting <code class="code">CRYPT_RSA_SMALLEST_PRIME</code>. Note that these must be done before a Crypt_RSA()
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object is initialized.
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</p><p>
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Smaller values for <code class="code">CRYPT_RSA_SMALLEST_PRIME</code> result in increased speed at the cost of security.
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</p></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="misc_crypt_rsa_format"></a>4.2.4. setPrivateKeyFormat(), setPublicKeyFormat(), loadKey() and setPassword()</h3></div></div></div><p>Crypt_RSA supports the following formats:</p><p>CRYPT_RSA_PRIVATE_FORMAT_PKCS1:</p><pre class="programlisting">-----BEGIN RSA PRIVATE KEY-----
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MIICWgIBAAKBgHx5XHa3LjiugtNq2xkd0oFf2SdsJ04hQYLoeRR3bqAei3Gc+PSy
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AvynCIh/03JCvBsUHaCe8BwjwaTYrpq5QunGo/wvIzvx2d3G9dlrpOIFLiatZYOf
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h07+CkSfaRXhBUKkul/gU87WPhKEcbnPDJS10uD1HqLsHfSKLNitGOf7AgElAoGA
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ENIhQHmedlzFkjEI2eFveURNxw6dhxlANEjtxH7XmRjiaUyQWGsVKQ+nNQpa2Bbb
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JkD9FbSc/OI8wz/gPmwP9eJN29CriebhaV3ebM1L1gbb5r7Vf/D/6rxB0BG/h2lA
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jyZWEZrV/Gi9ZCaw/J+IUu1pAskKid84yHphvszywCUCQQDigrtr+cVkwkUsxOGd
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B378yQCroXmybAD7FQHwVslafuFfTHkaMQSU/ZZLVY1ioMs1VVzzq/vOu0RstZOY
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AfHFAkEAjK3mIWdG4JOM44/SrDkACNatsMtXKOi4K3SlXu9ie6ikXPD+GSZ+bWCX
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GstFaXr9cHRvZPF3qYtK+j2N9UXOvwJBALeoRO/DmSFDkgifoixLRF5CHDgiD6Vs
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U9J/vGIBLaNSHoSe3rtKVr3+CyhTNF3Oe0AABi1bA4UGioGn+yFNr0UCQBbQF3sJ
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1CRq9ECT3PlVWfOYbzFtFQ2NhaYul1uAw9yzkEZsROF73SZ+XbFRZTOzFFds08su
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E2eaDCiUXDWcnhECQQCRUQn2huHlssj8kt35NAVwiHCNfaeSQ5tiDcwfOywA4YXl
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Q+kpuWq5U3V8j/9/n7pE/DL0nXEG/3QpKHJEYV5T
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-----END RSA PRIVATE KEY-----</pre><p>CRYPT_RSA_PRIVATE_FORMAT_PKCS1 (with password):</p><pre class="programlisting">-----BEGIN RSA PRIVATE KEY-----
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Proc-Type: 4,ENCRYPTED
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DEK-Info: DES-EDE3-CBC,0AE1DB47E71463BE
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pI2Kk5ceURbMYNo1xQqqA5rm2/QP4hgj/HuvrACtPSz/aesbG+h4lYXGpQ9os6Ha
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AyFW+iX2UWS6BRwJj1ztO20sKT6ckg7eINSfiSSAeOOiG5aHLxOYayO9aQ5UrrJX
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r0QmwRJRiHTW/82PLBNzfFHYskslNI9EWA5L/Gg4NAXDWwDooGvGkDq3ex7WkWLr
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k7DN2JoZuWsUZxwpgTDouRQMsygrsdSjwRDSgbnTn6luEBrL9fc5/oAWf0xoTk5h
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XMiOOHPBNPiZ1883ayq91HL/6895g8U9oIR1wQmdl0USViYYp5jI19ueowCyblzP
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xD3Bfpb6RPaZ/yqECOysPk6PDz257SGDMNk/QrQJ/eZkeniNXHJ8d+nJGuajZeBu
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6A/bglvKGNNNWe8UJMb5P2OAliD7y7F9wXrkV5FnQ/Q49tGxdBl7WXNuGp4x2d9s
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ZEnv3mOtrr1lM+2QE0Zg8mjqSem5b6Dp0LxOj5j45j5IbBrrd3MKu87jJVzp8yHy
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sBC6NMYYtO03qxV/j1kJR+MmAcCF1+4GGRWdFcoc0sXGVqmEOmK4QfYx3T0Vb6Hk
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oLdlh6ofZogezzJ8A1BvV382sTsJ90eqbgz3E+fDl8iR86+EV9bUujFE4IaBgZJP
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gxikVItdTcq1frNKTCSH/RPeRwk+oKWTpCYGgNA+bl641onW1DCLYcd14N6TDKmY
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77cOTf2ZDGOYNPycAF/FnNJJyLO3IYpU63aKBshB4dYeVrfH0FvG6g5Xt0geIkiD
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5W9El4ks7/3r97x443SagDRt6Mceo5TtzzFfAo7cZeA=
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-----END RSA PRIVATE KEY-----</pre><p>CRYPT_RSA_PUBLIC_FORMAT_PKCS1:</p><pre class="programlisting">-----BEGIN PUBLIC KEY-----
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MIGGAoGAfHlcdrcuOK6C02rbGR3SgV/ZJ2wnTiFBguh5FHduoB6LcZz49LIC/KcIiH/TckK8GxQd
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oJ7wHCPBpNiumrlC6caj/C8jO/HZ3cb12Wuk4gUuJq1lg5+HTv4KRJ9pFeEFQqS6X+BTztY+EoRx
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uc8MlLXS4PUeouwd9Ios2K0Y5/sCASU=
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-----END PUBLIC KEY-----</pre><p>CRYPT_RSA_PUBLIC_FORMAT_OPENSSH:</p><pre class="programlisting">ssh-rsa AAAAB3NzaC1yc2EAAAABJQAAAIB8eVx2ty44roLTatsZHdKBX9knbCdOIUGC6HkUd26gHotx
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nPj0sgL8pwiIf9NyQrwbFB2gnvAcI8Gk2K6auULpxqP8LyM78dndxvXZa6TiBS4mrWWDn4dO/gpEn2kV
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4QVCpLpf4FPO1j4ShHG5zwyUtdLg9R6i7B30iizYrRjn+w== phpseclib-generated-key</pre><p>
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Passwords can be set via <code class="code">setPassword()</code> and are only supported on private keys.
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CRYPT_RSA_PUBLIC_FORMAT_OPENSSH generates keys that are intended to go in $HOME/.ssh/authorized_keys
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for use with OpenSSH. Another format - CRYPT_RSA_PUBLIC_FORMAT_RAW - is stored as an array with two
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indexes - one for the modulus and one for the exponent. Indexes accepted by <code class="code">loadkey()</code>
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are as follows:
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</p><p>
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e, exponent, publicExponent, modulus, modulo, n
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</p><p>
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<code class="code">loadKey()</code> has two parameters - <code class="code">$key</code> and the optional <code class="code">$type</code>.
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The default type, if <code class="code">$type</code> is not explicitely set, is CRYPT_RSA_PRIVATE_FORMAT_PKCS1.
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It should, at this point, be noted that Crypt_RSA treats public and private keys largelly identically.
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A key can be formatted as a CRYPT_RSA_PUBLIC_FORMAT_PKCS1 and still conform to the
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CRYPT_RSA_PRIVATE_FORMAT_PKCS1 format and vice versa. The only real difference between private keys and
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public keys is that private keys *can* contain their public key counterparts whereas public keys cannot.
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That said, this distinction is, for the most part, irrelevant and academic. For a more thorough
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discussion of this see <a class="link" href="misc_crypt.html#misc_crypt_rsa_getpublickey" title="4.2.5. setPublicKey() and getPublicKey()">setPublicKey() and getPublicKey()</a>.
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</p></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="misc_crypt_rsa_getpublickey"></a>4.2.5. setPublicKey() and getPublicKey()</h3></div></div></div><p>
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As noted in <a class="link" href="misc_crypt.html#misc_crypt_rsa_format" title="4.2.4. setPrivateKeyFormat(), setPublicKeyFormat(), loadKey() and setPassword()">setPrivateKeyFormat(), setPublicKeyFormat(), loadKey() and setPassword()</a>,
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Crypt_RSA treats public and private keys largely identically. The only real difference is that some
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private key formats contain the public key within them whereas no public key format does. The reason
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you'd want to do this is for indexing purposes. For example, in SSH-2, RSA authentication works by
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sending your public key along with a signature created by your private key. The SSH-2 server then looks
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the public key up in an index of public keys to see if it's an allowed key and then verifies the signature.
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To that end, <code class="code">setPublicKey()</code> defines the public key if it hasn't already been defined and
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<code class="code">getPublicKey()</code> returns it. <code class="code">getPublicKey()</code> has an optional parameter - $type -
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that sets the format.
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</p></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="misc_crypt_rsa_encrypt"></a>4.2.6. encrypt(), decrypt() and setEncryptionMode()</h3></div></div></div><p>
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Crypt_RSA supports two encryption modes - <code class="code">CRYPT_RSA_ENCRYPTION_OAEP</code> and
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<code class="code">CRYPT_RSA_ENCRYPTION_PKCS1</code>. <code class="code">CRYPT_RSA_ENCRYPTION_OAEP</code> uses
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<a class="ulink" href="http://en.wikipedia.org/wiki/Optimal_Asymmetric_Encryption_Padding" target="_top">Optimal Asymmetric Encryption Padding</a>
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and provides more security than <code class="code">CRYPT_RSA_ENCRYPTION_PKCS1</code>.
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</p><p>
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Both <code class="code">CRYPT_RSA_ENCRYPTION_OAEP</code> and <code class="code">CRYPT_RSA_ENCRYPTION_PKCS1</code> impose limits
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on how large the plaintext can be. If the plaintext exceeds these limits the plaintext will be split
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up such that each block falls within those limits.
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</p></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="misc_crypt_rsa_sign"></a>4.2.7. sign(), verify(), and setSignatureMode()</h3></div></div></div><p>
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Crypt_RSA supports two signature modes - <code class="code">CRYPT_RSA_SIGNATURE_PSS</code> and
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<code class="code">CRYPT_RSA_SIGNATURE_PKCS1</code>. The former is assumed to provide more security than the latter.
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See <a class="link" href="misc_crypt.html#misc_crypt_rsa_examples" title="4.2.2. Examples">Examples</a> for examples.
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</p></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="misc_crypt_rsa_params"></a>4.2.8. setHash(), setMGFHash() and setSaltLength()</h3></div></div></div><p>
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In all likelihood, calling these functions will be unnecessary as the default values should be sufficient.
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None-the-less a discussion of them follows.
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</p><p>
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<code class="code">setHash()</code> is used with signature production / verification and (if the encryption mode is
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CRYPT_RSA_ENCRYPTION_OAEP) encryption and decryption. If the specified hash isn't supported sha1 will
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be used.
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</p><p>
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<code class="code">setMGFHash()</code> determines which hashing function should be used for the mask generation
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function as utilized in CRYPT_RSA_ENCRYPTION_OAEP and CRYPT_RSA_SIGNATURE_PSS. PKCS#1 recommends
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but does not require that the MGFHash and the Hash be set to the same thing.
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</p><p>
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<code class="code">setSaltLength()</code> is only utilized with CRYPT_RSA_SIGNATURE_PSS. PKCS#1 recommends this
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value either be 0 (which is what it is by default) or the length of the output of the hash function as
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set via <code class="code">setHash()</code>
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</p></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="sym_crypt.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="net.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 3. Symmetric-key Cryptography </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 5. Networking</td></tr></table></div></body></html>
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