As a major move to the more secure SHA-2 algorithm, Microsoft will allow the Secure Hash Algorithm 1 (SHA-1) Trusted Root Certificate Authority to expire. Beginning May 9, 2021 at 4:00 PM Pacific Time, all major Microsoft processes and services—including TLS certificates, code signing and file hashing—will use the SHA-2 algorithm exclusively.
The SHA-1 hash algorithm has become less secure over time because of the weaknesses found in the algorithm, increased processor performance, and the advent of cloud computing. Stronger alternatives such as the Secure Hash Algorithm 2 (SHA-2) are now strongly preferred as they do not experience the same issues. As a result, Microsoft has changed the signing of Windows updates to use the more secure SHA-2 algorithm exclusively in 2019 and subsequently retired all Windows-signed SHA-1 content from the Microsoft Download Center on August 3, 2020.
The Microsoft SHA-1 Trusted Root Certificate Authority expiration will impact SHA-1 certificates chained to the Microsoft SHA-1 Trusted Root Certificate Authority only. Manually installed enterprise or self-signed SHA-1 certificates will not be impacted; however they strongly encourage your organization to move to SHA-2 if you have not done so already.
Microsoft expect the SHA-1 certificate expiration to be uneventful. All major applications and services have been tested, and they have conducted a broad analysis of potential issues and mitigations. If you do encounter an issue after the SHA-1 retirement, please see Issues you might encounter when SHA-1 Trusted Root Certificate Authority expires. In addition, Microsoft Customer Service & Support teams are standing by and ready to support you.