1=pod
2
3=head1 NAME
4
5PKCS7_encrypt - create a PKCS#7 envelopedData structure
6
7=head1 SYNOPSIS
8
9PKCS7 *PKCS7_encrypt(STACK_OF(X509) *certs, BIO *in, const EVP_CIPHER *cipher, int flags);
10
11=head1 DESCRIPTION
12
13PKCS7_encrypt() creates and returns a PKCS#7 envelopedData structure. B<certs>
14is a list of recipient certificates. B<in> is the content to be encrypted.
15B<cipher> is the symmetric cipher to use. B<flags> is an optional set of flags.
16
17=head1 NOTES
18
19Only RSA keys are supported in PKCS#7 and envelopedData so the recipient certificates
20supplied to this function must all contain RSA public keys, though they do not have to
21be signed using the RSA algorithm.
22
23EVP_des_ede3_cbc() (triple DES) is the algorithm of choice for S/MIME use because
24most clients will support it.
25
26Some old "export grade" clients may only support weak encryption using 40 or 64 bit
27RC2. These can be used by passing EVP_rc2_40_cbc() and EVP_rc2_64_cbc() respectively.
28
29The algorithm passed in the B<cipher> parameter must support ASN1 encoding of its
30parameters. 
31
32Many browsers implement a "sign and encrypt" option which is simply an S/MIME 
33envelopedData containing an S/MIME signed message. This can be readily produced
34by storing the S/MIME signed message in a memory BIO and passing it to
35PKCS7_encrypt().
36
37The following flags can be passed in the B<flags> parameter.
38
39If the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are prepended
40to the data.
41
42Normally the supplied content is translated into MIME canonical format (as required
43by the S/MIME specifications) if B<PKCS7_BINARY> is set no translation occurs. This
44option should be used if the supplied data is in binary format otherwise the translation
45will corrupt it. If B<PKCS7_BINARY> is set then B<PKCS7_TEXT> is ignored.
46
47=head1 RETURN VALUES
48
49PKCS7_encrypt() returns either a valid PKCS7 structure or NULL if an error occurred.
50The error can be obtained from ERR_get_error(3).
51
52=head1 BUGS
53
54The lack of single pass processing and need to hold all data in memory as
55mentioned in PKCS7_sign() also applies to PKCS7_verify().
56
57=head1 SEE ALSO
58
59L<ERR_get_error(3)|ERR_get_error(3)>, L<PKCS7_decrypt(3)|PKCS7_decrypt(3)>
60
61=head1 HISTORY
62
63PKCS7_decrypt() was added to OpenSSL 0.9.5
64
65=cut
66