PKCS7_encrypt (3)

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NAME

PKCS7_encrypt - create a PKCS#7 envelopedData structure

SYNOPSIS

 #include <openssl/pkcs7.h>

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

EVP_des_ede3_cbc() (triple

) 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

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

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

and passing it to PKCS7_encrypt().

The following flags can be passed in the flags parameter.

If the

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

Normally the supplied content is translated into

canonical format (as required by the S/MIME specifications) if 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 is set then is ignored.

If the

flag is set a partial structure is output suitable for streaming I/O: no data is read from the in.

NOTES

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

Several functions including SMIME_write_PKCS7(), i2d_PKCS7_bio_stream(), PEM_write_bio_PKCS7_stream() finalize the structure. Alternatively finalization can be performed by obtaining the streaming

directly using BIO_new_PKCS7().

RETURN VALUES

PKCS7_encrypt() returns either a structure or if an error occurred. The error can be obtained from ERR_get_error(3).

SEE ALSO

ERR_get_error(3), PKCS7_decrypt(3)

HISTORY

PKCS7_decrypt() was added to OpenSSL 0.9.5 The flag was first supported in OpenSSL 1.0.0.