Incident Response, TDR, Vulnerability Management

Yahoo Mail shifts to SSL by default, but lacks perfect forward secrecy

Internet services corporation Yahoo announced on Tuesday that SSL encryption is now the default in Yahoo Mail – as signified by the HTTPS in front of the URL – but without perfect forward secrecy (PFS), some people are of the opinion that the effort is not enough.

“Anytime you use Yahoo Mail – whether it's on the web, mobile web, mobile apps, or via IMAP, POP or SMTP – it is 100 percent encrypted by default and protected with 2,048 bit certificates,” Jeff Bonforte, senior vice president of communication products with Yahoo, wrote in a short blog post.

Bonforte explained in the post that the encryption extends to emails, attachments and contacts, as well as Calendar and Messenger in Mail, but despite the long-awaited effort, at least one expert is not impressed by Yahoo's effort.

In a Wednesday email to, Tod Beardsley, Metasploit Engineering Manager at security firm Rapid7, said that he finds Yahoo's lack of support for PFS to be troubling.

Without PFS, an individual who records an encrypted session can decrypt the session later if they get their hands on Yahoo's private key, Beardsley said. He explained someone could do this through an exploit on the webmail provider's servers or through a weakness on the cipher itself, as well as via webmail operator cooperation or court-issued warrant.

Encryption techniques that utilize PFS have no single master key and are made possible due to a cryptographic key exchange known as Diffie-Hellman.

Seth Schoen, senior staff technologist with Electronic Frontier Foundation, told on Friday that he thinks it is great to see HTTPS being incorporated as a basic security feature. As far as Yahoo's effort is concerned, he said companies will always prioritize security differently.

“Whether it's enough depends on what you're looking to defend against, and we will certainly ask tech companies to keep working to protect their users,” Schoen said. “Forward secrecy is one important thing that should be done to mitigate the damage of things like what happened to Lavabit – and maybe other kinds of attacks and government requests that we don't even know about yet.”

Google, Facebook, Twitter, Dropbox and Tumblr are some of the companies that have already implemented PFS and Microsoft announced in December 2013 that it would be implementing PFS before the end of 2014.

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