  The ability to quickly revoke a compromised key is critical to the security
of any public-key infrastructure. Regrettably, most traditional certificate
revocation schemes suffer from latency, availability, or privacy problems.
These problems are exacerbated by the lack of a native delegation mechanism in
TLS, which increasingly leads domain owners to engage in dangerous practices
such as sharing their private keys with third parties.
  We analyze solutions that address the long-standing delegation and revocation
shortcomings of the web PKI, with a focus on approaches that directly affect
the chain of trust (i.e., the X.509 certification path). For this purpose, we
propose a 19-criteria framework for characterizing revocation and delegation
schemes. We also show that combining short-lived delegated credentials or proxy
certificates with an appropriate revocation system would solve several pressing
problems.
