The drivers must be signed to be installed under Windows Vista 64 bits. But what signature is this?

For drivers, there are two types of signatures:

• The digital signature of the binary: the driver is signed by the company issuing the driver.
  To do this just requires a digital signature from one of the bodies approved by Microsoft (-> http://www.microsoft.com/whdc/winlogo/drvsign/crosscert.mspx), to download the associated cross-certificate and to sign your own driver.
  It can now be installed under Windows Vista 64 bits.
  This signature does not delete warning messages at the time of installation.
• The WHQL certification: the signature produced by Microsoft validates the fact that the driver has passed the Microsoft certification tests and that it corresponds to the minimum required in terms of reliability.
  With this signature, there are no longer warning messages during the installation. As a result, a complete pre-installation of driver is possible (once the installation is complete, the driver is automatically loaded and the system does not seek the user anymore).