DATA ENCRYPTION: APPLICATIONS AND LIMITS
In a recent article,1 Bruce Schneier discussed how the information age practice of encrypting data at rest deviates from the historical use of cryptography for protecting data while it is communicated or in transit. One of Schneier's key points is that for data in motion, encryption keys can be ephemeral, whereas for data at rest, keys must be retained for as long as the stored data is kept encrypted. As Schneier points out, this does not reduce the number of things that must be stored secretly; it just makes those things smaller (the size of a key is far smaller than a typical data file). As Schneier states: "This whole model falls apart on the Internet.
Much of the data stored on the Internet is only peripherally intended for use by people; it's primarily intended for use by other computers. And therein lies the problem. Keys can no longer be stored in people's brains. They need to be stored on the same computer, or at least the network, that the data resides on. And that is much riskier."2 In meeting this challenge, there has been a recent rise in the number of security appliances that are intended to address this and related security implementation issues for data security in clouds.
When you need to use cryptography in your cloud implementation, remember:
- Developing cryptographic algorithms is a specialized and difficult challenge.
- Correctly implementing cryptography in software is nearly as difficult.
- Many products use cryptography in deeply flawed ways.
- A single flaw in cryptography undermines security, much as a weak link compromises the integrity of the entire chain.
- Many commercial and free cryptographic products have been shown to be insecure. There is a long history of products that do not work as claimed, products that are flawed, and products that use algorithms that have not been subjected to the test of time or the scrutiny of other cryptographers. Based on past experiences, it is wise to be skeptical about claims regarding a new product with a revolutionary or patent-pending cryptographic algorithm or some secret technique. The road to better cryptography is littered with products that failed to meet some or all advertised claims.
- Especially to be avoided are products that use secret cryptographic algorithms. Pick a cryptographic solution that is based on a recognized algorithm that has withstood the test of time and whose implementation has been tested by a recognized testing organization.
- Pick a known product that uses a thoroughly vetted algorithm and obtain it through secure means—don't download cryptographic or security software from Internet-based servers without the means to verify the content.
1. Schneier B. http://www.schneier.com/blog/archives/2010/06/data_at_rest_vs.html
; 2010 [accessed 7.10.10].