CODEX 1.1 review

CODEX is a software designed for applications with a moderate number of clients requesting authentication keys When designing secu

License: BSD License File size: 307K Developer: Michael A. Marsh

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CODEX is a software designed for applications with a moderate number of clients requesting authentication keys

When designing secure applications, it is not uncommon to assume some out-of-band mechanism for distributing keys or other secrets. Other applications without inherent security features could, given a key distribution system, employ symmetric key encryption to add a cryptographic access control mechanism. These applications motivated the development of the CODEX (the Cornell Data Exchange) key distribution system. CODEX is designed for applications with a moderate number of clients (tens or hundreds) requesting keys that change often but not continuously (on the scale of minutes to hours).

CODEX is an moving forward from the ideas implemented in COCA. It employs the RSA and ElGamal encryption schemes, as well as techniques such as threshold cryptography and proactive secret sharing. The COCA page contains a number of useful links for these topics.

Part of the development of CODEX was the creation of a general-purpose toolkit for the various primitives needed by the system. These primitives are discussed in the Implementation section, and the full source code is also available.

Since a random search on Google revealed that this project is now listed on Freshmeat, it is worth mentioning a few significant aspects of the implementation. First, the code is research-quality, not production-quality. The system employs spin-waiting, which can substantially impact the host on which a server runs. For an effective proactive-recovery system, servers must periodically be placed into a known-good state.

This typically involves rebooting from clean (and, if necessary, patched) media and installing new server-specific public/private key pairs, as well as the proactive secret sharing procedure included in the implementation. If, at this point, you still trust the implementation and your operating system enough to use CODEX, be advised that there is currently no credentials mechanism in place.

The existing policy object always accepts any credentials object as valid. Since the entire system depends on enforcing policies for access control, if you want to deploy a CODEX system (as opposed to using the libraries to build your own system) you must implement an actual policy/credentials mechanism.