Key Management Insights

If you want to use encryption, you need to use keys. A key is (or rather should be) a random number that can encrypt or decrypt your information. A strong key is strong because the random nature of the chosen number means it could lie anywhere on a virtually endless number line. As readers of this blog will know, once you have a strong key, effective key management is essential to ensure the data it protects remains secure.

A recent study (which I referenced in a previous post) found that a small percentage (0.38%) of over 7 million public keys share a common factor and subsequently can be easily compromised. As Bruce Schneier recognises in his blog post, these 'weak' keys were almost certainly created with a poor random number generator. A poor random number generator does not create 'random' numbers, only 'psuedorandom' numbers i.e. numbers generated by a predictable process. Keys based on pseudorandom numbers are liable to compromise, meaning that data encrypted with such keys are not secure.

Just last week a new example of the consequences of inadequately protected signature keys came to light. As reported in Network World , Kaspersky Lab discovered that a recently distributed Trojan, Mediyes, was digitally signed using a stolen private signature key whose digital certificate was owned by Swiss firm Conpavi AG.

The Network World story notes how digitally signed code is assessed more favorably by anti-virus vendors from a risk perspective, so stealing the key and creating a perfectly valid signature on the code helps further promulgate the nefarious Trojan before it can be detected.