Migrating from SHA-1 to SHA-2: what’s all the fuss about?

Created on May 24 2017, 5:32 PM by Rufus Connell

At the beginning of 2017, SHA-1 collisions quickly became a reality. With millions of TLS certificates still relying on the SHA-1 based signature algorithm for data integrity, upgrading to SHA-2 certificates is now a critical necessity.

Firefox and Chrome have already ended their support of SHA-1 TLS certificates, and Safari is set to follow suit this spring. For those still using the deprecated hash function, the security and reputation of your website is at greater risk.

Symantec has long supported the move to SHA-256 signed certificates and now we are urging you to make the switch as soon as possible, if you haven’t already.

What are SHA-1’s biggest flaws?

While the NSA officially deprecated SHA-1 in 2011, in February 2017, Google and CWI Amsterdam exposed its theoretical vulnerabilities in practice. 

Growing computational power is increasing the probability and affordability of these collisions. Google’s success proves two disparate data files can now obtain the same digital signature in a viable timeframe. This weakness can be abused to target vulnerable TLS and SSL certificates, allowing bad actors to certify malicious websites and code by assigning them the hash function of an authorised certificate.

Posing as a Certificate Authority (CA), an attacker can sign their own certificates using SHA-1’s vulnerability and appear to hold the private key of a legitimate certificate. Browsers won’t flag these certificates as rogue because the hash function features in their list of trusted signatures. The attackers can then redirect users to a malicious website, maintaining the HTTPS security icons of the original.

Since SSL and TLS certificates are synonymous with data protection, a reliance on SHA-1 could spark widespread manipulation from hackers in the near future.

Why is SHA-256 so superior?

SHA-256 is significantly different from SHA-1, and addresses all the vulnerabilities present in its predecessor. By switching to SHA-256, website owners can protect against the rising likelihood of an attack. While a SHA-256 collision is achievable in theory, in practice it would take today’s top-performing processors billions of years to compute.

At a granular level, its superiority comes from its increased bit-size (256 bits compared to SHA-1’s 160). While this might not seem like a radical change, the bit-size of SHA-256 protects it against the brute force of current collision attacks.

With browsers now ending their support for SHA-1 certificates, websites and systems that continue to use the hash algorithm will soon find their SSL/TLS certificates untrusted. Since SHA-256 shows no signs of the same vulnerabilities, replacing outdated certificates will prevent issues with user access.

Why is now the right time to migrate?

Despite its known weaknesses, many website owners still employ the SHA-1 has in certificate encryption. Their reluctance to upgrade stems from three factors:

  • Migration time
  • Migration cost
  • Fear of technical issues

But these aren’t valid excuses, especially when you consider the consequences of not upgrading. By the end of spring, all major browsers will have ended their support for SHA-1. These changes affect active SSL/TLS certificates as well as expiring ones, flagging your site as untrusted when users attempt to connect. The only way to avoid this inconvenience is to make the switch to SHA-256.

With Symantec, you can migrate in four simple steps:

  1. Inventory your certificates. Discover and manage your SSL/TLS certificates with the Symantec Certificate Intelligence Center. You can deploy this tool to check for existing SHA-1 certificates.
  2. Replace all SHA-1 certificates. Once you’ve located all SHA-1 certificates, create a new Certificate Signing Request (CRS) for each, and submit it to Symantec. While this takes time, it’s a crucial step in protecting your website’s future. We’ll renew every certificate with SHA-2 for free. 
  3. Install new certificates. The next step is to install these certificates on you network. Follow our installation advice to ensure you’re installing them correctly on your specific server vendor.
  4. Test your certificates. Use our CryptoReport tool to check for successful SSL/TLS certificate installations and remove cross-root certificates to ensure better performance and security compliance.

Audit and secure all your defences

SHA-1 is the most talked about vulnerability in cybersecurity right now, but you shouldn’t neglect or forget to patch other weak links in your system defences. Our Complete Website Security package includes SSL/TLS certificate assessment, DDoS protection and a Secure App Service so you can focus on converting leads and generating profit.

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