When PKCS_SMIME_CAPABILITIES or szOID_RSA_SMIMECapabilities are used for the lpszStructType with CryptEncodeObject, CryptEncodeObjectEx, CryptDecodeObject, or CryptDecodeObjectEx the following details apply.
"1.2.840.113549.1.9.15"
pvStructInfo points to a CRYPT_SMIME_CAPABILITIES structure.
For CryptEncodeObject and CryptEncodeObjectEx (X509_ASN_ENCODING), Parameters.cbData == 0 causes the encoded parameters to be omitted and not encoded as a NULL (05 00) as is done when encoding a CRYPT_ALGORITHM_IDENTIFIER. This is per the S/MIME specification for encoding capabilities.