Firefox blocks websites with vulnerable encryption keys

Users will receive an error when trying to access web servers that use weak Diffie-Hellman key exchange with weak keys

To protect users from cryptographic attacks that can compromise secure web connections, the popular Firefox browser will block access to HTTPS servers that use weak Diffie-Hellman keys.

Diffie-Hellman is a key exchange protocol that is slowly replacing the widely used RSA key agreement for the TLS  (Transport Layer Security) protocol. Unlike RSA, Diffie-Hellman can be used with TLS's ephemeral modes, which provide forward secrecy -- a property that prevents the decryption of previously captured traffic if the key is cracked at a later time.

However, in May 2015 a team of researchers devised a downgrade attack that could compromise the encryption connection between browsers and servers if those servers supported DHE_EXPORT, a version of Diffie-Hellman key exchange imposed on exported cryptographic systems by the U.S. National Security Agency in the 1990s and which limited the key size to 512 bits. In May 2015 around 7 percent of websites on the internet were vulnerable to the attack, which was dubbed LogJam.

"In response to recent developments attacking Diffie-Hellman key exchange and to protect the privacy of Firefox users, we have increased the minimum key size for TLS handshakes using Diffie-Hellman key exchange to 1023 bits," David Keeler, a Mozilla security engineer, said in a blog post Friday.

A small number of servers are still not configured to use strong enough keys and Firefox users trying to access them will receive an error called “ssl_error_weak_server_ephemeral_dh_key," Keeler said.

According to a recent survey of the top 140,000 HTTPS websites on the internet by traffic, around 5 percent of them used keys smaller than 1024 bits. The currently recommended size is 2048 bits and over 67 percent of these sites conform to that.

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Lucian Constantin

IDG News Service
Show Comments

Cool Tech

Toys for Boys

Family Friendly

Stocking Stuffer

SmartLens - Clip on Phone Camera Lens Set of 3

Learn more >

Christmas Gift Guide

Click for more ›

Brand Post

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Aysha Strobbe

Microsoft Office 365/HP Spectre x360

Microsoft Office continues to make a student’s life that little bit easier by offering reliable, easy to use, time-saving functionality, while continuing to develop new features that further enhance what is already a formidable collection of applications

Michael Hargreaves

Microsoft Office 365/Dell XPS 15 2-in-1

I’d recommend a Dell XPS 15 2-in-1 and the new Windows 10 to anyone who needs to get serious work done (before you kick back on your couch with your favourite Netflix show.)

Maryellen Rose George

Brother PT-P750W

It’s useful for office tasks as well as pragmatic labelling of equipment and storage – just don’t get too excited and label everything in sight!

Cathy Giles

Brother MFC-L8900CDW

The Brother MFC-L8900CDW is an absolute stand out. I struggle to fault it.

Luke Hill

MSI GT75 TITAN

I need power and lots of it. As a Front End Web developer anything less just won’t cut it which is why the MSI GT75 is an outstanding laptop for me. It’s a sleek and futuristic looking, high quality, beast that has a touch of sci-fi flare about it.

Emily Tyson

MSI GE63 Raider

If you’re looking to invest in your next work horse laptop for work or home use, you can’t go wrong with the MSI GE63.

Featured Content

Product Launch Showcase

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?