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Security

Revisiting Security Fundamentals

Steve Goeringer
Distinguished Technologist, Security

Oct 17, 2019

It’s Cybersecurity Awareness Month—time to study up!

Cybersecurity is a complex topic. The engineers who address cybersecurity must not only be security experts; they must also be experts in the technologies they secure. In addition, they have to understand the ways that the technologies they support and use might be vulnerable and open to attack.

Another layer of complexity is that technology is always evolving. In parallel with that evolution, our adversaries are continuously advancing their attack methods and techniques. How do we stay on top of that? We must be masters of security fundamentals. We need to be able to start with foundational principals and extend our security tools, techniques and methods from there: Make things no more complex than necessary to ensure safe and secure user experiences.

In celebration of Cybersecurity Awareness Month, I’d like to devote a series of blog posts to address some basics about security and to provide a fresh perspective on why these concepts remain important areas of focus for cybersecurity.

Three Goals

At the most basic level, the three primary goals of security for cable and wireless networks are to ensure the confidentiality, integrity and availability of services. NIST documented these concepts well in its special publication, “An Introduction to Information Security.”

  • Confidentiality ensures that only authorized users and systems can access a given resource (e.g., network interface, data file, processor). This is a pretty easy concept to understand: The most well-known confidentiality approach is encryption.
  • Integrity, which is a little more obscure, guards against unauthorized changes to data and systems. It also includes the idea of non-repudiation, which means that the source of a given message (or packet) is known and cannot be denied by that source.
  • Availability is the uncelebrated element of the security triad. It’s often forgotten until failures in service availability are recognized as being “a real problem.” This is unfortunate because engineering to ensure availability is very mature.

In Part 1 of this series, I want to focus on confidentiality. I’ll discuss integrity and availability in two subsequent blogs.

As I mentioned, confidentiality is a security function that most people are aware of. Encryption is the most frequently used method to assure confidentiality. I’m not going to go into a primer about encryption. However, it is worth talking about the principles. Encryption is about applying math using space, power and time to ensure that only parties with the right secret (usually a key) can read certain data. Ideally, the math used should require much greater space, power or time for an unauthorized party without the right secret to read that data. Why does this matter? Because encryption provides confidentiality only as long as the math used is sound and that the corresponding amount of space, power and time for adversaries to read the data is impractical. That is often a good assumption, but history has shown that over time, a given encryption solution will eventually become insecure. So, it’s a good idea to apply other approaches to provide confidentiality as well.

What are some of those approaches? Ultimately, the other solutions prevent access to the data being protected. The notion is that if you prevent access (either physically or logically) to the data being protected, then it can’t be decrypted by unauthorized parties. Solutions in this area fall primarily into two strategies: access controls and separation.

Access controls validate that requests to access data or use a resource (like a network) come from authorized sources (identified using network addresses and other credentials). For example, an access control list (ACL) is used in networks to restrict resource access to specific IP or MAC addresses. As another example, a cryptographic challenge and response (often enabled by public key cryptography) might be used to ensure that the requesting entity has the “right credentials” to access data or a resource. One method we all use every day is passwords. Every time we “log on” to something, like a bank account, we present our username (identification) and our (hopefully) secret password.

Separation is another approach to confidentiality. One extreme example of separation is to establish a completely separate network architecture for conveying and storing confidential information. The government often uses this tactic, but even large enterprises use it with “private line networks.” Something less extreme is to use some form of identification or tagging to encapsulate packets or frames so that only authorized endpoints can receive traffic. This is achieved in ethernet by using virtual LANs (VLANs). Each frame is tagged by the endpoint or the switch to which it connects with a VLAN tag, and only endpoints in the same VLAN can receive traffic from that source endpoint. Higher network layer solutions include IP Virtual Private Network (VPNs) or, sometimes, Multiprotocol Label Switching (MPLS).

Threats to Confidentiality

What are the threats to confidentiality? I’ve already hinted that encryption isn’t perfect. The math on which a given encryption approach is based can sometimes be flawed. This type of flaw can be discovered decades after the original math was developed. That’s why it’s traditionally important to use cipher suites approved by appropriate government organizations such as NIST or ENISA. These organizations work with researchers to develop, select, test and validate given cryptographic algorithms as being provably sound.

However, even when an algorithm is sound, the way it’s implemented in code or hardware may have systemic errors. For example, most encryption approaches require the use of random number generators to execute certain functions. If a given code library for encryption uses a random number generator that’s biased in some way (less than truly random), the space, power and time necessary to achieve unauthorized access to encrypted data may be much less than intended.

One threat considered imminent to current cryptography methods is quantum computing. Quantum computers enable new algorithms that reduce the power, space and time necessary to solve certain specific problems, compared with what traditional computers required. For cryptography, two such algorithms are Grover’s and Shor’s.

Grover’s algorithm. Grover’s quantum algorithm addresses the length of time (number of computations) necessary to do unstructured search. This means that it may take half the number of guesses necessary to guess the secret (the key) to read a given piece of encrypted data. Given current commonly used encryption algorithms, which may provide confidentiality against two decades’ worth of traditional cryptanalysis, Grover’s algorithm is only a moderate threat—until you consider that systemic weaknesses in some implementations of those encryption algorithms may result in less than ideal security.

Shor’s algorithm. Shor’s quantum algorithm is a more serious threat specifically to asymmetric cryptography. Current asymmetric cryptography relies on mathematics that assume it’s hard to factor integers down to primes (such as used by the Rivest-Shamir-Adleman algorithm) or to guess given numbers in a mathematical function or field (such as used in elliptical curve cryptography). Shor’s quantum algorithm makes very quick work of factoring; in fact, it may be possible to factor these mathematics nearly instantly given a sufficiently large quantum computer able to execute the algorithm.

It’s important to understand the relationship between confidentiality and privacy. They aren’t the same. Confidentiality protects the content of a communication or data from unauthorized access, but privacy extends beyond the technical controls that protect confidentiality and extends to the business practices of how personal data is used. Moreover, in practice, a security infrastructure may for some data require it to be encrypted while in motion across a network, but perhaps not when at rest on a server. Also, while confidentiality, in a security context, is pretty much a straight forward technical topic, privacy is about rights, obligations and expectations related to the use of personal data.

Why do I bring it up here? Because a breach of confidentiality may also be a breach of privacy. And because application of confidentiality tools alone does not satisfy privacy requirements in many situations. Security engineers – adversarial engineers – need to keep these things in mind and remember that today privacy violations result in real costs in fines and brand damage to our companies.

Wow! Going through all that was a bit more involved than I intended – lets finish this blog. Cable and wireless networks have implemented many confidentiality solutions. WiFi, LTE, and DOCSIS technology all use encryption to ensure confidentiality on the shared mediums they use to transport packets. The cipher algorithm DOCSIS technology typically uses AES128 which has stood the test of time. We can anticipate future advances. One is a NIST initiative to select a new light weight cipher – something that uses less processing resources than AES. This is a big deal. For just a slight reduction in security (measured using a somewhat obscure metric called “security bits”), some of the candidates being considered by NIST may use half the power or space as compared to AES128. That may translate to lower cost and higher reliability of end-points that use the new ciphers.

Another area the cable industry, including CableLabs, continues to track is quantum resistant cryptography. There are two approaches here. One is to use quantum technologies (to generate keys or transmit data) that may be inherently secure against quantum computer based cryptanalysis. Another approach is to use quantum resistant algorithms (e.g., new math that is resistant to  cryptanalysis using Shor’s and Grover’s  algorithms) implemented on traditional computing methods. Both approaches are showing great promise.

There’s a quick review of confidentiality. Next up? Integrity.

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