Secret data for the credential. The CredentialBlob member can be both read and written.
If the `Type` member is `CredentialType.DomainPassword`, this member contains the plaintext Unicode password for `UserName`.
The `CredentialBlob` and `CredentialBlobSize` members do not include a trailing zero character.
Also, for `CredentialType.DomainPassword`, this member can only be read by the authentication packages.
If the Type member is `CredentialType.DomainCertificate`, this member contains the clear test Unicode PIN for `UserName`.
The `CredentialBlob` and `CredentialBlobSize` members do not include a trailing zero character.
Also, this member can only be read by the authentication packages.
If the `Type` member is `CredentialType.Generic`, this member is defined by the application.
Credentials are expected to be portable. Applications should ensure that the data in `CredentialBlob` is portable.