BOX ES.3
Public Key Systems

Public key systems (sometimes implemented as public key infrastructures, or PKIs) employ a sophisticated approach to authentication that relies heavily on cryptography. Public key cryptography is often touted as a virtual panacea for e–commerce and e-government authentication and confidentiality challenges; however, implementation and deployment details are key to this technology’s effectiveness, security, usability, and privacy protection. A critical component of some public key systems is a certificate authority (CA) that will certify that a particular key belongs to a particular individual. One way to implement this functionality is to use a public CA (or trusted third party) to certify keys for multiple users and organizations. This practice, however, places much control in a centralized location, raising privacy and security concerns.

The complexity of public key systems has made their ease of use and deployment a challenge. Getting the underlying cryptography right is only half the battle. Users must be educated with respect to how the systems should be used for maximum effectiveness. Certificates must be distributed securely and revoked when necessary. These systems require considerable storage, bandwidth, and computational ability. Their privacy implications depend on how they are implemented and used. The scope of the PKI (as with any authentication system) will be one determinant of how grave the attendant privacy risks are. At one end of the spectrum is a PKI designed to operate in a limited context (for example, in a single organization or for a single function), and at the other end are PKIs that attempt to provide service to a very large population for a broad set of purposes.

Finding: Many of the problems that appear to be intrinsic to public key infrastructures (as opposed to specific public key infrastructure products) seem to derive from the scope of the public key infrastructure. (5.5)

Recommendation: Public key infrastructures should be limited in scope in order to simplify their deployment and to limit adverse privacy effects. Software such as browsers should provide better support for private (versus public) certificate authorities and for the use of private keys and certificates among multiple computers associated with the same user to facilitate the use of private certificate authorities. (5.3)

Finding: Public certificate authorities and trusted third parties could present significant privacy and security concerns. (5.3)

Finding: Public key infrastructures have a reputation for being difficult to use and hard to deploy. Current products do little to dispel this notion. (5.4)