ProtonMail on Thursday introduced a new feature designed to make it more difficult for hackers and spammers to impersonate users who have custom domain email addresses.
The new feature, DKIM key management, is currently in beta and users have been encouraged to share feedback to help ProtonMail developers improve it.
Email addresses are often spoofed for phishing and scams, but individuals and organizations can implement measures to prevent malicious actors from impersonating their email addresses.
One such measure is DomainKeys Identified Mail, or DKIM, an email authentication method designed to detect forged sender addresses by adding a digital signature to the header of each email. The signature is linked to the user’s domain name and it’s created with a private key that has a corresponding public key added to the domain registrar’s DNS.
If DKIM is used, the email recipient’s server looks up the public key and uses it to verify the signature in the message’s header to ensure that the email is legitimate.
ProtonMail has supported DKIM, but the new key management feature makes it easier to rotate keys — create a new key and retire the old one — by automating the process.
“DKIM requires the public key to be published on your domain registrar’s DNS, which means these keys can be targeted by attackers. Hackers can access your public key and try to crack its RSA encryption. If they can crack it, then they can spoof your key and impersonate your custom domain,” Proton’s Richie Koch explained in a blog post.
“Currently, 1024-bit RSA keys are on the edge of what can be cracked (given very specialized equipment and plenty of time) while 2048-bit RSA keys are considered immune to cracking. This is why we recommend you use 2048-bit keys,” Koch added. “Still, to be safe, security experts suggest you get a new DKIM public key every six months to prevent your address from being spoofed, or anytime you fear your key may have been compromised.”