CPExportKey

The CPExportKey function is used to export cryptographic keys out of the CSP in a secure manner.

BOOL CPExportKey(
  HCRYPTPROV hProv,  // in
  HCRYPTKEY hKey,    // in
  HCRYPTKEY hExpKey, // in
  DWORD dwBlobType,  // in
  DWORD dwFlags,     // in
  BYTE *pbData,      // out
  DWORD *pdwDataLen  // in, out
);
 

Parameters

hProv

Handle to a particular key container (or "context") within the CSP. This handle is obtained via a call to CPAcquireContext.

hKey

Handle to the key to be exported.

hExpKey

Handle to a cryptographic key belonging to the destination user. The key data within the key blob created is encrypted using this key. This ensures that only the destination user will be able to make use of the key blob.

Most often, this will be the key exchange public key of the destination user. Certain protocols, however, require that a session key belonging to the destination user be used for this purpose.

If the key blob is not to be encrypted (for example, the key blob type is PUBLICKEYBLOB), then this parameter is unused, and should be zero.

dwBlobType

Type of key blob to be exported. The following three key blob types are currently defined:

• SIMPLEBLOB—used to transport session keys
• PUBLICKEYBLOB—used to transport public keys
• PRIVATEKEYBLOB—used to transport public/private key pairs

Additional key blob types will be defined as needed.

dwFlags

Flag values. No flags are currently defined.

pbData

Buffer into which the function places the key blob.

If this parameter is NULL, then no data should be copied. Instead, the required buffer size (in bytes) should be returned in pdwDataLen. This is not an error.

pdwDataLen

Address of the key blob length. Upon function entry, this contains the number of bytes in the pbData buffer. Upon exit, this must be set to the number of bytes of data copied to the pbData buffer.

If the buffer specified by pbData is not large enough to hold the key blob data, the ERROR_MORE_DATA error code should be returned via the SetLastError function. In this case, the required buffer size must be returned in pdwDataLen.

If this function fails with any error code other than ERROR_MORE_DATA, zero should be returned in this parameter.

Return Values

If the function succeeds, TRUE should be returned; otherwise, return FALSE. When FALSE is returned, the appropriate error code (see the following table) must be set via SetLastError.

See Also

CPImportKey, CryptExportKey