PKCS7_encrypt(3)

     NAME
          PKCS7_encrypt - create a PKCS#7 envelopedData structure

     SYNOPSIS
          PKCS7 *PKCS7_encrypt(STACK_OF(X509) *certs, BIO *in, const
          EVP_CIPHER *cipher, int flags);

     DESCRIPTION
          PKCS7_encrypt() creates and returns a PKCS#7 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.

     NOTES
          Only RSA keys are supported in PKCS#7 and envelopedData so
          the recipient certificates supplied to this function must
          all contain RSA public keys, though they do not have to be
          signed using the RSA algorithm.

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

          Some old "export grade" clients may only support weak
          encryption using 40 or 64 bit RC2. These can be used by
          passing EVP_rc2_40_cbc() and EVP_rc2_64_cbc() respectively.

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

          Many browsers implement a "sign and encrypt" 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
          PKCS7_encrypt().

          The following flags can be passed in the flags parameter.

          If the PKCS7_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 PKCS7_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 PKCS7_BINARY
          is set then PKCS7_TEXT is ignored.

     RETURN VALUES
          PKCS7_encrypt() returns either a valid PKCS7 structure or
          NULL if an error occurred.  The error can be obtained from
          ERR_get_error(3).
     BUGS
          The lack of single pass processing and need to hold all data
          in memory as mentioned in PKCS7_sign() also applies to
          PKCS7_verify().

     SEE ALSO
          ERR_get_error(3), PKCS7_decrypt(3)

     HISTORY
          PKCS7_decrypt() was added to OpenSSL 0.9.5