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.\" ========================================================================
.\"
.IX Title "PKCS7_ENCRYPT 3ossl"
.TH PKCS7_ENCRYPT 3ossl "2026-01-16" "3.5.1" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH "NAME"
PKCS7_encrypt_ex, PKCS7_encrypt
\&\- create a PKCS#7 envelopedData structure
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/pkcs7.h>
\&
\& PKCS7 *PKCS7_encrypt_ex(STACK_OF(X509) *certs, BIO *in,
\&                         const EVP_CIPHER *cipher, int flags,
\&                         OSSL_LIB_CTX *libctx, const char *propq);
\& PKCS7 *PKCS7_encrypt(STACK_OF(X509) *certs, BIO *in, const EVP_CIPHER *cipher,
\&                      int flags);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBPKCS7_encrypt_ex()\fR creates and returns a PKCS#7 envelopedData structure.
\&\fIcerts\fR is a list of recipient certificates. \fIin\fR is the content to be
encrypted. \fIcipher\fR is the symmetric cipher to use. \fIflags\fR is an optional set
of flags. The library context \fIlibctx\fR and the property query \fIpropq\fR are used
when retrieving algorithms from providers.
.PP
Only \s-1RSA\s0 keys are supported in PKCS#7 and envelopedData so the recipient
certificates supplied to this function must all contain \s-1RSA\s0 public keys, though
they do not have to be signed using the \s-1RSA\s0 algorithm.
.PP
\&\fBEVP_des_ede3_cbc()\fR (triple \s-1DES\s0) is the algorithm of choice for S/MIME use
because most clients will support it.
.PP
Some old \*(L"export grade\*(R" clients may only support weak encryption using 40 or 64
bit \s-1RC2.\s0 These can be used by passing \fBEVP_rc2_40_cbc()\fR and \fBEVP_rc2_64_cbc()\fR
respectively.
.PP
The algorithm passed in the \fBcipher\fR parameter must support \s-1ASN1\s0 encoding of
its parameters.
.PP
Many browsers implement a \*(L"sign and encrypt\*(R" 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 \s-1BIO\s0 and passing it to
\&\fBPKCS7_encrypt()\fR.
.PP
The following flags can be passed in the \fBflags\fR parameter.
.PP
If the \fB\s-1PKCS7_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are
prepended to the data.
.PP
Normally the supplied content is translated into \s-1MIME\s0 canonical format (as
required by the S/MIME specifications) if \fB\s-1PKCS7_BINARY\s0\fR 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 \fB\s-1PKCS7_BINARY\s0\fR is set then
\&\fB\s-1PKCS7_TEXT\s0\fR is ignored.
.PP
If the \fB\s-1PKCS7_STREAM\s0\fR flag is set a partial \fB\s-1PKCS7\s0\fR structure is output
suitable for streaming I/O: no data is read from the \s-1BIO\s0 \fBin\fR.
.PP
If the flag \fB\s-1PKCS7_STREAM\s0\fR is set the returned \fB\s-1PKCS7\s0\fR structure is \fBnot\fR
complete and outputting its contents via a function that does not
properly finalize the \fB\s-1PKCS7\s0\fR structure will give unpredictable
results.
.PP
Several functions including \fBSMIME_write_PKCS7()\fR, \fBi2d_PKCS7_bio_stream()\fR,
\&\fBPEM_write_bio_PKCS7_stream()\fR finalize the structure. Alternatively finalization
can be performed by obtaining the streaming \s-1ASN1\s0 \fB\s-1BIO\s0\fR directly using
\&\fBBIO_new_PKCS7()\fR.
.PP
\&\fBPKCS7_encrypt()\fR is similar to \fBPKCS7_encrypt_ex()\fR but uses default
values of \s-1NULL\s0 for the library context \fIlibctx\fR and the property query \fIpropq\fR.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBPKCS7_encrypt_ex()\fR and \fBPKCS7_encrypt()\fR return either a \s-1PKCS7\s0 structure
or \s-1NULL\s0 if an error occurred. The error can be obtained from \fBERR_get_error\fR\|(3).
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBERR_get_error\fR\|(3), \fBPKCS7_decrypt\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
The function \fBPKCS7_encrypt_ex()\fR was added in OpenSSL 3.0.
.PP
The \fB\s-1PKCS7_STREAM\s0\fR flag was added in OpenSSL 1.0.0.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2002\-2020 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the Apache License 2.0 (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.
