Redmond had earlier said that Windows would block SHA-1 signed TLS (Transport Layer Security) certificates from January 1, 2017, but is now mulling moving up the date to June.

There have been concerns about the algorithm’s security as researchers have proven that a forged digital certificate that has the same SHA-1 hash as a legitimate one can be created. 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In October, a team of cryptoanalysts warned that the SHA-1 standard should be withdrawn as the cost of breaking the encryption had dropped faster than expected to US$75,000 to $120,000 in 2015 using freely available cloud computing.

Programme manager for Microsoft Edge Kyle Pflug wrote in his blog that Redmond will coordinate with other browser vendors to evaluate the impact of this timeline based on telemetry and current projections for feasibility of SHA-1 collisions.

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 January 1, 2017.