The Redmond-based software maker had earlier said that Windows would block SHA-1 signed TLS (Transport Layer Security) certificates from Jan. 1, 2017, but is now mulling moving up the date in view of recent advances in attacks on the SHA-1 algorithm, a cryptographic hash function designed by the U.S. National Security Agency.
There have been concerns about the security of the algorithm, which led Microsoft, Google and Mozilla to announce that their browsers would stop accepting SHA-1 SSL (Secure Sockets Layer) certificates.
Researchers have proven that a forged digital certificate that has the same SHA-1 hash as legitimate one can be created, and users can then be tricked into interacting with a spoofed site in what is called a hash collision.
In October, a team of cryptoanalysts warned that the SHA-1 standard should be withdrawn sooner than the companies proposed as the cost of breaking the encryption had dropped faster than expected to US$75,000 to $120,000 in 2015 using freely available cloud computing facilities, making a SHA-1 collision affordable by online criminal groups.
"We will continue to coordinate with other browser vendors to evaluate the impact of this timeline based on telemetry and current projections for feasibility of SHA-1 collisions," Kyle Pflug, program manager for Microsoft Edge, wrote in a blog post Wednesday.
Mozilla said in October that in view of recent attacks it was considering a cut-off of July 1, 2016 to start rejecting all SHA-1 SSL certificates, regardless of when they were issued, ahead of an earlier scheduled date of Jan. 1, 2017.