The TAG value for this optional setting is 0x0009. The LENGTH value for this setting MUST be larger than 4. The DATA field contains the SHA1 Hash setting, as specified in [RFC3174], which is used to look up the signing certificate in the certificate store on the user's computer.<29>
For a specified PtypBinary ([MS-OXCDATA] section 2.11.1) value in the PidTagUserX509Certificate property (section 18.104.22.168), if the SignSHA1Hash setting is present, the SignCertificate setting MUST NOT be present.
The client and the server SHOULD use the SignCertificate setting instead of the SignSHA1Hash setting.