For FIDO support, a FIDO key supported by Windows 10.

This is typically provided by the smart card manufacturer although many common hardware tokens are supported by OpenSC.

For PKCS support, a PKCS #11 library (typically a DLL file) is needed to interface with the hardware token.

For CAPI support, an appropriate Windows smart card mini-driver must be installed.You can download the latest release of PuTTY CAC here: Prerequisites PuTTY CAC is maintained independently from the US Government by the open source community.

The 'CAC' in 'PuTTY CAC' refers to Common Access Card, a smart card token used for US Government facilities which was one of the initial drivers for the development of PuTTY CAC. PuTTY CAC can be used with many types of cryptographic tokens such as Yubikeys and popular smart card models. PuTTY CAC adds the ability to use the Windows Certificate API (CAPI), Public Key Cryptography Standards (PKCS) libraries, or Fast Identity Online (FIDO) keys to perform SSH public key authentication using a private key associated with a certificate that is stored on a hardware token. PuTTY CAC is a fork of PuTTY, a popular Secure Shell (SSH) terminal.

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