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SHA-1 collision attacks are now actually practical and a looming danger

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Attacks on the SHA-1 hashing algorithm just got a lot more dangerous last week with the discovery of the first-ever “chosen-prefix collision attack,” a more practical version of the SHA-1 collision attack first carried out by Google two years ago.

What this means is that SHA-1 collision attacks can now be carried out with custom inputs, and they’re not just accidental mishaps anymore, allowing attackers to target certain files to duplicate and forge.

SHA-1 collision attacks

The SHA-1 hashing function was theoretically broken in 2005; however, the first successful collision attack in the real world was carried out in 2017.

Two years ago, academics from Google and CWI produced two files that had the same SHA-1 hash, in the world’s first ever SHA-1 collision attack –known as “SHAttered.”

Cryptographers predicted SHA-1 would be broken in a real-world scenario, but the SHAttered research came three years earlier than they expected, and also cost only $110,000 to execute using cloud-rented computing power, far less than what people thought it might cost.

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Image: Google

SHA-1 chosen-prefix attacks

But last week, a team of academics from France and Singapore has taken the SHAttered research one step further by demonstrating the first-ever SHA-1 “chosen-prefix” collision attack, in a new research paper titled “From Collisions to Chosen-Prefix Collisions – Application to Full SHA-1.”

“Finding a practical collision attack breaks the hash function badly of course, but the actual damage that can be done with such a collision is somewhat limited as the attacker will have little to no control on the actual data that collides,” Thomas Peyrin, one of the researcher told ZDNet via email over the weekend.

“A much more interesting attack is to find a so-called ‘chosen-prefix collision,’ where the attacker can freely choose the prefix for the two colliding messages. Such collisions change everything in terms of threat because you can now consider having collisions with meaningful data inside (like names or identities in a digital certificate, etc).”

What this means is that SHA-1 collision attacks aren’t a game of roulette anymore, and now, threat actors can forge any SHA-1-signed documents they want, ranging from business documents to TLS certificates.

SHA-1 chosen-prefix collision attacks are now also cheap

But the work of Peyrin and his colleague –Gaetan Leurent– have done goes far beyond than proving SHA-1 chosen-prefix collision attacks are theoretically possible.

They also showed that such attacks are now cheap and in the budget of cybercrime and nation-state attackers.

“These chosen-prefix collisions are believed to be much harder to find than classical collisions. For SHA-1, the best previous search method required 2^77 SHA-1 evaluations, which remained out of reach in practice,” Peyrin told ZDNet.

“The novelty in our article is that we explain how to drastically reduce the cost of finding chosen-prefix collisions for SHA-1, down to almost the same cost as finding a classical collision,” he said.

“We are currently working on further improvements (unpublished yet), and we evaluate now that one can find a chosen-prefix collision for SHA-1 with a budget of less than $100,000, which is really practical.”

This is about the same cost as the original SHAttered research, yet, this version of the attack is what attackers would likely use if they’d ever want to attack SHA-1-protected data.

“We have tested all subcomponents of the attack, but we have not tried to compute a chosen-prefix collision example,” Peyrin said.

“Our initial estimations were $1 million to compute the chosen-prefix collision, which is an amount of money we simply don’t have. Thanks to our latest improvements, the cost went down below $100,000 and we are currently working on computing the first chosen-prefix collision for SHA-1.

“Hopefully, we will be able to announce new results soon,” the researcher said.

Moving away from SHA-1

Browser vendors have long ago started deprecating support for SHA-1-signed TLS traffic inside their products; however, other applications still rely on it.

“There are still many users with older browsers and many protocols and software that allow SHA-1 signatures. Concretely, it is still possible to buy an SHA-1 certificate from a trusted CA, and many email clients accept an SHA-1 certificate when opening a TLS connection,” Peyrin told us.

“SHA-1 is also widely supported to authenticate TLS and IKE handshake messages. Now, what protocol can be attacked and to what extent is hard to tell at the moment, because it needs careful scrutiny of the inner working of the protocol and how the digital signatures / certificates are used, etc..

“However, what we can say is that our attack put at possible risk products using digital signatures, or certificates based on SHA-1,” Peyrin said.

“The take-home message should really be that using SHA-1 for digital
signatures or certificates is very dangerous, and should not be allowed. People doing so are strongly advised to change to SHA-2 or SHA-3 now.”

What to use?

“The attacks against SHA-1 are only going to get better,” Scott Arciszewski, Chief Development Officer at Paragon Initiative Enterprises, and a leading cryptographer, told ZDNet in a separate email.

“Everyone should switch to (in order of preference):

  • BLAKE2b / BLAKE2s
  • SHA-512/256
  • SHA3-256
  • SHA-384
  • Any other SHA2-family hash function as a last resort

“…unless they’re storing passwords! In which case, they should switch to (in order of preference):

  • Argon2id with memory >= 32MiB, >= 2 rounds, and >= 2 parallelism
  • scrypt / yescrypt with memory >= 32 MiB, >= 4 rounds, and >= 1 parellelism
  • bcrypt (for PHP devs, password_hash() and password_verify() does the trick)
  • PBKDF2-SHA512 with 85,000 iterations as a last resort

“But SHA1 should no longer be used anymore. No excuses,” Arciszewski said.

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Phish Fight: Securing Enterprise Communications

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Yes, much of the world may have moved on from email to social media and culturally dubious TikTok dances, yet traditional electronic mail remains a foundation of business communication. And sadly, it remains a prime vector for malware, data leakage, and phishing attacks that can undermine enterprise protections. It doesn’t have to be that way.

In a just released report titled “GigaOm Radar for Phishing Prevention and Detection,” GigaOm Analyst Simon Gibson surveyed more than a dozen enterprise-focused email security solutions. He found a range of approaches to securing communications that often can be fitted together to provide critical, defense-in-depth protection against even determined attackers.

Figure 1. GigaOm Radar for Email Phishing Prevention and Detection

“When evaluating these vendors and their solutions, it is important to consider your own business and workflow,” Gibson writes in the report, stressing the need to deploy solutions that best address your organization’s business workflow and email traffic. “For some it may be preferable to settle on one comprehensive solution, while for others building a best-of-breed architecture from multiple vendors may be preferable.”

In a field of competent solutions, Gibson found that Forcepoint, purchased recently by Raytheon, stood apart thanks to the layered protections provided by its Advanced Classification Engine. Area 1 and Zimperium, meanwhile, are both leaders that exhibit significant momentum, with Area 1 boosted by its recent solution partnership with Virtru, and Zimperium excelling in its deep commitment to mobile message security.

A mobile focus is timely, Gibson says in a video interview for GigaOm. He says companies are “tuning the spigot on” and enabling unprecedented access and reliance on mobile devices, which is creating an urgent need to get ahead of threats.

Gibson’s conclusion in the report? He singles out three things: Defense in depth, awareness of existing patterns and infrastructure, and a healthy respect for the “human factor” that can make security so hard to lock down.

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When Is a DevSecOps Vendor Not a DevSecOps Vendor?

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DevOps’ general aim is to enable a more efficient process for producing software and technology solutions and bringing stakeholders together to speed up delivery. But we know from experience that this inherently creative, outcome-driven approach often forgets about one thing until too late in the process—security. Too often, security is brought into the timeline just before deployment, risking last minute headaches and major delays. The security team is pushed into being the Greek chorus of the process, “ruining everyone’s fun” by demanding changes and slowing things down.

But as we know, in the complex, multi-cloud and containerized environment we find ourselves in, security is becoming more important and challenging than ever. And the costs of security failure are not only measured in slower deployment, but in compliance breaches and reputational damage.

The term “DevSecOps” has been coined to characterize how security needs to be at the heart of the DevOps process. This is in part principle and part tools. As a principle, DevSecOps fits with the concept of “shifting left,” that is, ensuring that security is treated as early as possible in the development process. So far, so simple.

From a tooling perspective, however, things get more complicated, not least because the market has seen a number of platforms marketing themselves as DevSecOps. As we have been writing our Key Criteria report on the subject, we have learned that not all DevSecOps vendors are necessarily DevSecOps vendors. Specifically, we have learned to distinguish capabilities that directly enable the goals of DevSecOps from a process perspective, from those designed to support DevSecOps practices. We could define them as: “Those that do, and those that help.”

This is how to tell the two types of vendor apart and how to use them.

Vendors Enabling DevSecOps: “Tools That Do”

A number of tools work to facilitate the DevSecOps process -– let’s bite the bullet and call them DevSecOps tools. They help teams set out each stage of software development, bringing siloed teams together behind a unified vision that allows fast, high-quality development, with security considerations at its core. DevSecOps tools work across the development process, for example:

  • Create: Help to set and implement policy
  • Develop: Apply guidance to the process and aid its implementation
  • Test: Facilitate and guide security testing procedures
  • Deploy: Provide reports to assure confidence to deploy the application

The key element that sets these tool sets apart is the ability to automate and reduce friction within the development process. They will prompt action, stop a team from moving from one stage to another if the process has not adequately addressed security concerns, and guide the roadmap for the development from start to finish.

Supporting DevSecOps: “Tools That Help”

In this category we place those tools which aid the execution, and monitoring, of good DevSecOps principles. Security scanning and application/infrastructure hardening tools are a key element of these processes: Software composition analysis (SCA) forms a part of the development stage, static/dynamic application security testing (SAST/DAST) is integral to the test stage and runtime app protection (RASP) is a key to the Deploy stage.

Tools like this are a vital part of the security layer of security tooling, especially just before deployment – and they often come with APIs so they can be plugged into the CI/CD process. However, while these capabilities are very important to DevSecOps, they can be seen in more of a supporting role, rather than being DevSecOps tools per se.

DevSecOps-washing is not a good idea for the enterprise

While one might argue that security should never have been shifted right, DevSecOps exists to ensure that security best practices take place across the development lifecycle. A corollary exists to the idea of “tools that help,” namely that organizations implementing these tools are not “doing DevSecOps,” any more than vendors providing these tools are DevSecOps vendors.

The only way to “do” DevSecOps is to fully embrace security at a process management and governance level: This means assessing risk, defining policy, setting review gates, and disallowing progress for insecure deliverables. Organizations that embrace DevSecOps can get help from what we are calling DevSecOps tools, as well as from scanning and hardening tools that help support its goals.

At the end of the day, all security and governance boils down to risk: If you buy a scanning tool so you can check a box that says “DevSecOps,” you are potentially adding to your risk posture, rather than mitigating it. So, get your DevSecOps strategy fixed first, then consider how you can add automation, visibility, and control using “tools that do,” as well as benefit from “tools that help.”

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High Performance Application Security Testing

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This free 1-hour webinar from GigaOm Research. It is hosted by an expert in Application and API testing, and GigaOm analyst, Jake Dolezal. His presentation will focus on the results of high performance testing we completed against two security mechanisms: ModSecurity on NGINX and NGINX App Protect. Additionally, we tested the AWS Web Application Firewall (WAF) as a fully managed security offering.

While performance is important, it is only one criterion for a Web Application Firewall selection. The results of the report are revealing about these platforms. The methodology will be shown with clarity and transparency on how you might replicate these tests to mimic your own workloads and requirements.

Register now to join GigaOm and sponsor NGINX for this free expert webinar.

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