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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minuteMicrosoft has deprecated Windows support for TLS server-authentication certificates using RSA keys shorter than 2048 bits. The change is narrower than “all 1024-bit certificates are invalid”: Microsoft says enterprise- and test-CA-issued TLS certificates are not impacted by this change, though it recommends upgrading their keys as a security best practice. Organizations should identify which machine certificates they own, where they are used, and how they will be replaced and renewed.
What Windows is deprecating—and what it is not
Microsoft Learn’s current Deprecated features in the Windows client entry says that “TLS server authentication certificates using RSA keys with key lengths shorter than 2048 bits” are deprecated. The policy describes RSA TLS server-authentication certificates as needing keys of at least 2048 bits to be considered valid by Windows.
The scope matters: this concerns certificates used to authenticate a server during TLS, not every certificate stored on a Windows computer, every certificate containing a 1024-bit RSA key, or every use of RSA. Microsoft says TLS certificates issued by enterprise or test CAs are not impacted by this change. It nevertheless recommends those issuers update to at least 2048-bit keys as a security best practice; that recommendation is not the same as saying the stated Windows enforcement applies to those certificates.
Microsoft’s 2024 announcement described the affected certificates as TLS server-authentication certificates chaining to roots in the Microsoft Trusted Root Program. It forecast deprecation in late 2024. That was a forecast made in 2024, not a new future deadline; use the current Windows client deprecation entry for the present policy wording.
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Why the threshold is 2048 bits
Microsoft says internet standards and regulatory bodies disallowed 1024-bit keys in 2013 and recommended RSA keys of at least 2048 bits. Its 2024 announcement attributes that 2013 recommendation to NIST. The point is the change in expected cryptographic strength, not that every older certificate has the same issuer, purpose, or Windows outcome.
Other Microsoft certificate timelines are easy to confuse with this one. The Microsoft Trusted Root Program requirements give examples of code-signing root algorithm lifetimes—RSA 1024 = 2014 and RSA 2048 = 2030. Those examples concern certain code-signing roots; they are not the schedule for TLS server-certificate enforcement. Likewise, Microsoft’s 2012 MSRC article, Microsoft’s continuing work on digital certificates, addressed hardening for RSA keys shorter than 1024 bits under a different policy context. Neither changes the later TLS server-authentication threshold described in the current Windows client entry.
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How to find and manage machine TLS certificates
The useful operational response is to establish ownership and lifecycle visibility, not to assume a particular inventory product is required. For each machine TLS certificate and endpoint, record:
- The accountable owner, service, endpoint, and certificate purpose.
- The issuer and full certificate chain, including whether issuance was from an enterprise or test CA.
- The public-key algorithm and key size, along with the certificate’s expiration date.
- How the certificate is issued, installed, renewed, and monitored for expiry.
- Which clients, services, or integrations depend on the certificate and chain.
Then work through the affected candidates methodically:
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- Locate TLS server certificates. Inventory certificates attached to machine and service endpoints; distinguish server authentication from other certificate purposes.
- Flag weak RSA keys. Identify TLS server-authentication certificates with RSA keys below 2048 bits. Confirm the issuing CA and chain rather than using key size alone to declare a certificate in scope.
- Prioritize replacements. Address certificates that fall within Microsoft’s stated scope first. Keep enterprise- and test-CA certificates visible as exceptions to this change, while planning key upgrades as appropriate security maintenance.
- Choose a compatible replacement. Microsoft identifies RSA keys of at least 2048 bits or ECDSA as stronger options. Check the algorithms supported by actual servers and dependent clients, as well as trust-chain support, issuance policy, key custody, and renewal automation.
- Test, deploy, and monitor. Test the replacement chain in the Windows environments that rely on it, deploy it, and verify that renewal and expiry monitoring work. Track any exception with an owner and a time limit.
A certificate lifecycle or PKI management service may help at enterprise scale, but it is an operational option—not a Microsoft requirement. No universal replacement algorithm is established by Microsoft’s recommendation: compatibility and the organization’s issuance and key-management practices determine the workable choice.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Are 1024-bit RSA certificates still accepted by Windows?
There is no single yes-or-no answer for every certificate. The current Microsoft wording addresses TLS server-authentication certificates using RSA keys shorter than 2048 bits and describes them as deprecated; it also expressly says enterprise- and test-CA-issued TLS certificates are not impacted by this change. The certificate’s purpose and issuer chain therefore matter. Microsoft’s cited guidance does not provide an affected-build-by-build mapping or a prevalence estimate for how many organizations are affected.
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