| Platform SDK: Cryptography |
The Symmetric Wrapped Key BLOB format is used to export and import a symmetric key wrapped with another symmetric key. The actual wrapped key is in the format specified in the IETF SMIME X9.42 standard.
BLOBHEADER blobheader; ALG_ID WrapAlgid; BYTE Blob[variable length];
This BLOB format is exported when the SYMMETRICWRAPKEYBLOB type is used with CryptExportKey. When exporting a BLOB of this type, both the hKey and hExpKey parameters to the CryptExportKey call must contain valid symmetric key handles. When calling CryptImportkey and using a BLOB of this type, the hImpKey parameter must contain a valid and correct handle to a symmetric key.
The following table describes each component of the key BLOB.
| Field | Description |
|---|---|
| Blobheader | BLOBHEADER structure. The bType member must have a value of SYMMETRICWRAPKEYBLOB, bVersion must be 2 and aiKeyAlgid must be the algorithm identifier for the wrapped key. |
| WrapAlgid | Algorithm identifier for the wrapping key. |
| Blob | BLOB value. This needs to be in the symmetric key wrapping format specified in the IETF SMIME X9.42 standard. |