Microsoft accidentally broke several things in the October 2025 Windows Update, but smart card authentication was not one of them. That was intentionally broken, and the temporary workaround requires a registry hack.

Redmond noted the issue last week after smart card authentication and other certificate operations started failing following an "improvement" made to Windows in light of CVE-2024-30098. Part of the mitigation was to require RSA-based smart card certificates to use KSP (Key Storage Provider) instead of CSP (Cryptographic Service Provider).

The upshot of this change is that certificates that use CSP might have problems after the update. These problems could manifest as an inability to sign documents, smart cards not being recognized as CSP providers in 32-bit applications, and

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