1=pod
2
3=head1 NAME
4
5PKCS7_encrypt - create a PKCS#7 envelopedData structure
6
7=head1 SYNOPSIS
8
9 #include <openssl/pkcs7.h>
10
11 PKCS7 *PKCS7_encrypt(STACK_OF(X509) *certs, BIO *in, const EVP_CIPHER *cipher, int flags);
12
13=head1 DESCRIPTION
14
15PKCS7_encrypt() creates and returns a PKCS#7 envelopedData structure. B<certs>
16is a list of recipient certificates. B<in> is the content to be encrypted.
17B<cipher> is the symmetric cipher to use. B<flags> is an optional set of flags.
18
19=head1 NOTES
20
21Only RSA keys are supported in PKCS#7 and envelopedData so the recipient certificates
22supplied to this function must all contain RSA public keys, though they do not have to
23be signed using the RSA algorithm.
24
25EVP_des_ede3_cbc() (triple DES) is the algorithm of choice for S/MIME use because
26most clients will support it.
27
28Some old "export grade" clients may only support weak encryption using 40 or 64 bit
29RC2. These can be used by passing EVP_rc2_40_cbc() and EVP_rc2_64_cbc() respectively.
30
31The algorithm passed in the B<cipher> parameter must support ASN1 encoding of its
32parameters. 
33
34Many browsers implement a "sign and encrypt" option which is simply an S/MIME 
35envelopedData containing an S/MIME signed message. This can be readily produced
36by storing the S/MIME signed message in a memory BIO and passing it to
37PKCS7_encrypt().
38
39The following flags can be passed in the B<flags> parameter.
40
41If the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are prepended
42to the data.
43
44Normally the supplied content is translated into MIME canonical format (as required
45by the S/MIME specifications) if B<PKCS7_BINARY> is set no translation occurs. This
46option should be used if the supplied data is in binary format otherwise the translation
47will corrupt it. If B<PKCS7_BINARY> is set then B<PKCS7_TEXT> is ignored.
48
49=head1 RETURN VALUES
50
51PKCS7_encrypt() returns either a valid PKCS7 structure or NULL if an error occurred.
52The error can be obtained from ERR_get_error(3).
53
54=head1 BUGS
55
56The lack of single pass processing and need to hold all data in memory as
57mentioned in PKCS7_sign() also applies to PKCS7_verify().
58
59=head1 SEE ALSO
60
61L<ERR_get_error(3)|ERR_get_error(3)>, L<PKCS7_decrypt(3)|PKCS7_decrypt(3)>
62
63=head1 HISTORY
64
65PKCS7_decrypt() was added to OpenSSL 0.9.5
66
67=cut
68