To support evolving industry security standards, and continue to keep you protected and productive, Microsoft will retire content that is Windows-signed for Secure Hash Algorithm 1 (SHA-1) from the Microsoft Download Center on August 3, 2020. This is the next step in our continued efforts to adopt Secure Hash Algorithm 2 (SHA-2), which better meets modern security requirements and offers added protections from common attack vectors.

SHA-1 is a legacy cryptographic hash that many in the security community believe is no longer secure. Using the SHA-1 hashing algorithm in digital certificates could allow an attacker to spoof content, perform phishing attacks, or perform man-in-the-middle attacks.

Microsoft no longer uses SHA-1 to authenticate Windows operating system updates due to security concerns associated with the algorithm, and has provided the appropriate updates to move customers to SHA-2 as previously announced. Accordingly, beginning in August 2019, devices without SHA-2 support have not received Windows updates. If you are still reliant upon SHA-1, we recommend that you move to a currently supported version of Windows and to stronger alternatives, such as SHA-2.

 

Source: Microsoft Tech Community