php-doc-en/reference/mcrypt/functions/mcrypt-encrypt.xml

<?xml version="1.0" encoding="utf-8"?>
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<refentry xml:id="function.mcrypt-encrypt" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>mcrypt_encrypt</refname>
  <refpurpose>Encrypts plaintext with given parameters</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>string</type><methodname>mcrypt_encrypt</methodname>
   <methodparam><type>string</type><parameter>cipher</parameter></methodparam>
   <methodparam><type>string</type><parameter>key</parameter></methodparam>
   <methodparam><type>string</type><parameter>data</parameter></methodparam>
   <methodparam><type>string</type><parameter>mode</parameter></methodparam>
   <methodparam choice="opt"><type>string</type><parameter>iv</parameter></methodparam>
  </methodsynopsis>
  <para>
   Encrypts the data and returns it.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>cipher</parameter></term>
     <listitem>
      &mcrypt.parameter.cipher;
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>key</parameter></term>
     <listitem>
      <para>
       The key with which the data will be encrypted. If it's smaller than
       the required keysize, it is padded with '<literal>\0</literal>'. It is
       better not to use ASCII strings for keys.
      </para>
      <para>
       It is recommended to use the mhash functions to create a key from a
       string.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>data</parameter></term>
     <listitem>
      <para>
       The data that will be encrypted with the given <parameter>cipher</parameter>
       and <parameter>mode</parameter>. If the size of the data is not n * blocksize,
       the data will be padded with '<literal>\0</literal>'.
      </para>
      <para>
       The returned crypttext can be larger than the size of the data that was
       given by <parameter>data</parameter>.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>mode</parameter></term>
     <listitem>
      &mcrypt.parameter.mode;
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>iv</parameter></term>
     <listitem>
      &mcrypt.parameter.iv;
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns the encrypted data, as a string.
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>mcrypt_encrypt</function> Example</title>
    <programlisting role="php">
<![CDATA[
<?php
    # --- ENCRYPTION ---

    # the key should be random binary, use scrypt, bcrypt or PBKDF2 to
    # convert a string into a key
    # key is specified using hexadecimal
    $key = pack('H*', "bcb04b7e103a0cd8b54763051cef08bc55abe029fdebae5e1d417e2ffb2a00a3");
    
    # show key size use either 16, 24 or 32 byte keys for AES-128, 192
    # and 256 respectively
    $key_size =  strlen($key);
    echo "Key size: " . $key_size . "\n";
    
    $plaintext = "This string was AES-256 / CBC / ZeroBytePadding encrypted.";

    # create a random IV to use with CBC encoding
    $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
    
    # use an explicit encoding for the plain text
    $plaintext_utf8 = utf8_encode($plaintext);
    
    # creates a cipher text compatible with AES (Rijndael block size = 128)
    # to keep the text confidential 
    # only suitable for encoded input that never ends with value 00h
    # (because of default zero padding)
    $ciphertext = mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key,
                                 $plaintext_utf8, MCRYPT_MODE_CBC, $iv);

    # prepend the IV for it to be available for decryption
    $ciphertext = $iv . $ciphertext;
    
    # encode the resulting cipher text so it can be represented by a string
    $ciphertext_base64 = base64_encode($ciphertext);

    echo  $ciphertext_base64 . "\n";

    # === WARNING ===

    # Resulting cipher text has no integrity or authenticity added
    # and is not protected against padding oracle attacks.
    
    # --- DECRYPTION ---
    
    $ciphertext_dec = base64_decode($ciphertext_base64);
    
    # retrieves the IV, iv_size should be created using mcrypt_get_iv_size()
    $iv_dec = substr($ciphertext_dec, 0, $iv_size);
    
    # retrieves the cipher text (everything except the $iv_size in the front)
    $ciphertext_dec = substr($ciphertext_dec, $iv_size);

    # may remove 00h valued characters from end of plain text
    $plaintext_utf8_dec = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key,
                                         $ciphertext_dec, MCRYPT_MODE_CBC, $iv_dec);
    
    echo  $plaintext_utf8_dec . "\n";
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
Key size: 32
ENJW8mS2KaJoNB5E5CoSAAu0xARgsR1bdzFWpEn+poYw45q+73az5kYi4j+0haevext1dGrcW8Qi59txfCBV8BBj3bzRP3dFCp3CPQSJ8eU=
This string was AES-256 / CBC / ZeroBytePadding encrypted.
]]>
    </screen>
   </example>
  </para>
  <para>
   See also <function>mcrypt_module_open</function> for a more advanced API
   and an example.
  </para>
 </refsect1>
</refentry>

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