It seems as though everywhere you turn lately, another story breaks revealing information about PRISM and Edward Snowden. And it just keeps coming. Snowden’s latest disclosure builds on the story that not only has the NSA partnered with cloud service providers to bypass encryption and access data on their international clients, but also that they have ‘cracked much online encryption.’ What does this mean for your security team? Should you quit using encryption?
The short (and long) answer is NO.
Interestingly, Snowden himself commented that strong encryption cannot be decoded by the NSA, and he was quoted by the Guardian during an online chat, "Encryption works. Properly implemented strong crypto systems are one of the few things you can rely on."
While the details are still murky regarding the NSA’s actual technical capabilities, Snowden’s recent revelations indicate the NSA has used a combination of endpoint security weaknesses, direct access granted by service providers, and potentially some mathematics to ‘crack’ the encryption used in SSL – the primary algorithm used for internet communications. But does this mean they can crack all encryption? No – or at least, not yet.
Let’s look at one of the most common forms of encryption, the AES standard. This is a primary encryption algorithm recommended by the National Institute of Standards and Technology (NIST). The AES algorithm, introduced in 2001, is used extensively (including by the government) to encrypt data ‘at rest’ in storage and in backups. Bruce Schneier, a famous cryptographer, has written about AES extensively in the past and has said many times that AES will take a long time to break, quite likely on the order of decades, centuries or even longer. In a recent blog after news of the NSA leak, Schneier wrote:
Honestly, I’m skeptical. Whatever the NSA has up its top-secret sleeves, the mathematics of cryptography will still be the most secure part of any encryption system. I worry a lot more about poorly designed cryptographic products, software bugs, bad passwords, companies that collaborate with the NSA to leak all or part of the keys, and insecure computers and networks. Those are where the real vulnerabilities are, and where the NSA spends the bulk of its efforts.
What exactly do we mean when we talk about about 'cracking' encryption? Encryption requires two components: 1) an algorithm that converts readable bits into unreadable bits, and 2) an encryption key which is needed to unlock (or decrypt) the data. A 'brute force attack' is the most common way to try to break encryption. The brute force method involves using massive compute power to systematically check all possible keys until the correct one is found. In the same blog post, Schneier explains that "the upper practical limit on brute force is somewhere under 80 bits."
By comparison, AES encryption is typically performed with a minimum of 128-bit keys and more often than not, 256-bit keys. Without diving into the mathematical details, encryption experts out there say a brute force attack on keys of this length is just plain impossible today. As a side note: both Intel and AMD have hardware support for AES 128 and 256 so that much of the encryption and decryption is now performed at hardware speeds. The difference in overhead between AES-128 and AES-256 is small enough that you should always use 256 bit keys.
So while brute force attacks are not yet feasible, we have already heard that many of the major cloud / internet companies have been co-operating with government authorities and handing over customer data. Are these companies also giving the NSA backdoors into their environments? We may never know the answer, and we’ll certainly see a lot more speculation.
Amid this flurry of Chicken Littles claiming the crypto sky is falling, should you just throw up your arms and stop using encryption? Absolutely not. Encryption, with strong key management is the safest method available today to protect your data and its use is becoming more and more pervasive especially as data is leaving the data center and heading to the cloud.
If you are using a public cloud, one of the primary questions you should ask yourself is "From whom do I want to protect my data?" In most cases, philosophical or political issues aside, I doubt the government is at the top of your list. It's critical to secure your data from unauthorized access. Here are some of the most common concerns that we hear:
1. The data is potentially accessible by privileged users at my cloud provider
2. My cloud provider is encrypting my data (but they also hold the encryption keys)
3. If our own government is overly nosy, what about governments of other countries or those conducting corporate espionage?
The solution to these worries is simple. Encrypt your data before moving it to the cloud. Encrypt it while it’s in the cloud and most importantly, keep the keys yourself. To quote Bruce Schneier once again, this time from the preface to his book “Practical Cryptography”:
Key management is the hardest part of cryptography and often the Achilles' heel of an otherwise secure system.
Remember, the cloud can still provide immense value to your organization. Don’t let hype overcome rational judgment and practical technology.