= Introduction = Different Windows versions have different kernel-mode signing options: * Windows 7/8/8.1/Server 2012r2 * Cross-signing * WHQL-certified (HCR) * Windows 10 desktop * Attestation signing * WHQL-certified (HLK) * Windows Server 2016/2019 * WHQL-certified (HLK) According to practical testing done by [https://www.wintun.net/ wintun] developers it is possible to cover all Windows 10 platforms with the following HLK clients: * Windows Server 2019 (64-bit) * Windows Server 2019 core (64-bit) * Windows 10 desktop (32-bit) Wintun was able to pass HLK testing without any physical HLK clients. But due to its narrower scope it had to pass much fewer HLK tests (~50 in total) than tap-windows6.