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<ul id="index">
 <li><a href="#NAME">NAME</a></li>
 <li><a href="#SYNOPSIS">SYNOPSIS</a></li>
 <li><a href="#DESCRIPTION">DESCRIPTION</a></li>
 <li><a href="#NOTES">NOTES</a></li>
 <li><a href="#NOTES1">NOTES</a></li>
 <li><a href="#RETURN-VALUES">RETURN VALUES</a></li>
 <li><a href="#SEE-ALSO">SEE ALSO</a></li>
 <li><a href="#HISTORY">HISTORY</a></li>
 <li><a href="#COPYRIGHT">COPYRIGHT</a></li>
</ul>

CMS_encrypt - create a CMS envelopedData structure

<h1 id="SYNOPSIS">SYNOPSIS</h1>

<pre><code> #include &lt;openssl/cms.h&gt;

CMS_ContentInfo *CMS_encrypt(STACK_OF(X509) *certs, BIO *in,
 const EVP_CIPHER *cipher, unsigned int flags);</code></pre>

<h1 id="DESCRIPTION">DESCRIPTION</h1>

CMS_encrypt() creates and returns a CMS EnvelopedData structure. certs is a list of recipient certificates. in is the content to be encrypted. cipher is the symmetric cipher to use. flags is an optional set of flags.

<h1 id="NOTES">NOTES</h1>

Only certificates carrying RSA, Diffie-Hellman or EC keys are supported by this function.

EVP_des_ede3_cbc() (triple DES) is the algorithm of choice for S/MIME use because most clients will support it.

The algorithm passed in the cipher parameter must support ASN1 encoding of its parameters.

Many browsers implement a &quot;sign and encrypt&quot; option which is simply an S/MIME envelopedData containing an S/MIME signed message. This can be readily produced by storing the S/MIME signed message in a memory BIO and passing it to CMS_encrypt().

The following flags can be passed in the flags parameter.

If the CMS_TEXT flag is set MIME headers for type text/plain are prepended to the data.

Normally the supplied content is translated into MIME canonical format (as required by the S/MIME specifications) if CMS_BINARY is set no translation occurs. This option should be used if the supplied data is in binary format otherwise the translation will corrupt it. If CMS_BINARY is set then CMS_TEXT is ignored.

OpenSSL will by default identify recipient certificates using issuer name and serial number. If CMS_USE_KEYID is set it will use the subject key identifier value instead. An error occurs if all recipient certificates do not have a subject key identifier extension.

If the CMS_STREAM flag is set a partial CMS_ContentInfo structure is returned suitable for streaming I/O: no data is read from the BIO in.

If the CMS_PARTIAL flag is set a partial CMS_ContentInfo structure is returned to which additional recipients and attributes can be added before finalization.

The data being encrypted is included in the CMS_ContentInfo structure, unless CMS_DETACHED is set in which case it is omitted. This is rarely used in practice and is not supported by SMIME_write_CMS().

<h1 id="NOTES1">NOTES</h1>

If the flag CMS_STREAM is set the returned CMS_ContentInfo structure is not complete and outputting its contents via a function that does not properly finalize the CMS_ContentInfo structure will give unpredictable results.

Several functions including SMIME_write_CMS(), i2d_CMS_bio_stream(), PEM_write_bio_CMS_stream() finalize the structure. Alternatively finalization can be performed by obtaining the streaming ASN1 BIO directly using BIO_new_CMS().

The recipients specified in certs use a CMS KeyTransRecipientInfo info structure. KEKRecipientInfo is also supported using the flag CMS_PARTIAL and CMS_add0_recipient_key().

The parameter certs may be NULL if CMS_PARTIAL is set and recipients added later using CMS_add1_recipient_cert() or CMS_add0_recipient_key().

<h1 id="RETURN-VALUES">RETURN VALUES</h1>

CMS_encrypt() returns either a CMS_ContentInfo structure or NULL if an error occurred. The error can be obtained from ERR_get_error(3).

<a href="../man3/ERR_get_error.html">ERR_get_error(3)</a>, <a href="../man3/CMS_decrypt.html">CMS_decrypt(3)</a>

<h1 id="HISTORY">HISTORY</h1>

The CMS_STREAM flag was first supported in OpenSSL 1.0.0.

<h1 id="COPYRIGHT">COPYRIGHT</h1>

Licensed under the OpenSSL license (the &quot;License&quot;). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <a href="https://www.openssl.org/source/license.html">https://www.openssl.org/source/license.html</a>.

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