Secure XML: The New Syntax for Signatures and Encryption

2.11. Other Facets of Security

Next, we look briefly at a few other important facets of a complete security system, albeit issues that are somewhat outside the scope of digital cryptography. An overall security system is only as secure as the weakest facet.

Key Rollover

No key should be used forever. The longer a key has been in use and the more often its uses are exposed, the greater the probability of it being compromised due to accident, subversion, or cryptanalysis. Most systems require regular key updates and a plan for nonscheduled rollover in case of known compromise. While the timing for such updates depends on the particular circumstances, most public keys should not be used for more than a year. In fact, sometimes it is reasonable to ...