CRYPT_DECRYPT_MESSAGE_PARA structure (wincrypt.h)

The CRYPT_DECRYPT_MESSAGE_PARA structure contains information for decrypting messages.

Syntax

typedef struct _CRYPT_DECRYPT_MESSAGE_PARA {
  DWORD      cbSize;
  DWORD      dwMsgAndCertEncodingType;
  DWORD      cCertStore;
  HCERTSTORE *rghCertStore;
  DWORD      dwFlags;
} CRYPT_DECRYPT_MESSAGE_PARA, *PCRYPT_DECRYPT_MESSAGE_PARA;

Members

cbSize

Size of this structure in bytes.

dwMsgAndCertEncodingType

Type of encoding used. It is always acceptable to specify both the certificate and message encoding types by combining them with a bitwise-OR operation as shown in the following example:

X509_ASN_ENCODING | PKCS_7_ASN_ENCODING

Currently defined encoding types are:

• X509_ASN_ENCODING
• PKCS_7_ASN_ENCODING

cCertStore

Number of elements in the rghCertStore array.

rghCertStore

Array of certificate store handles.

These certificate store handles are used to obtain the certificate context to use for decrypting a message. For more information, see the decryption functions CryptDecryptMessage, and CryptDecryptAndVerifyMessageSignature. An encrypted message can have one or more recipients. The recipients are identified by a unique certificate identifier, often the hash of the certificate issuer and serial number. The certificate stores are searched to find a certificate context corresponding to the unique identifier.

Recipients can also be identified by their KeyId. Both Key Agreement (Diffie-Hellman) and Key Transport (RSA) recipients are supported.

Only certificate contexts in the store with one of the following properties, CERT_KEY_PROV_INFO_PROP_ID, or CERT_KEY_CONTEXT_PROP_ID can be used. These properties specify the location of a needed private exchange key.

dwFlags

The CRYPT_MESSAGE_SILENT_KEYSET_FLAG can be set to suppress any UI by the CSP. For more information about the CRYPT_SILENT flag, see CryptAcquireContext.

Requirements

See also

CryptDecryptAndVerifyMessageSignature

CryptDecryptMessage