CNT4403 PKI

Public Key Infrastructure (PKI)

Is a system designed to securely distribute public keys through the use of certificates. While originally intended as a comprehensive solution to build trust on a global level, it faces significant challenges and risks.

Identity-Based Encryption (IBE)

A form of public-key cryptography where a public key can be an arbitrary string, like an email address, eliminating the need for public key distribution via certificates. Proposed by Shamir in 1984.

SDSI/SPKI

Simple Distributed Security Infrastructure / Simple Public Key Infrastructure. Parallel efforts to build a decentralized security system where trust is established through groups of keys declared by principals, rather than a centralized CA.

Revocation Failure -

Why PKI is Hard?

PKI is considered difficult because it attempts to solve the complex problem of establishing trust globally. A specific technical challenge within PKI is revocation, often described as the "anti-matter" problem. Revoking a certificate before its expiration is difficult.

Trust and Liability (Who do we trust, and for what?)

The core argument is that Certificate Authorities (CAs) are not inherently trustworthy and often defer legal liability for running a bad CA, leaving the risk with the certificate holder.

CA Compromise-

Key Security (Who is using my key?)

This risk focuses on the vulnerability of the private key, arguing that keys are fundamentally insecure and users are often held responsible for compromises.

Verifier Security (How secure is the verifier?)

The security of the entire system relies on the legitimacy of the verifier's root public key. The argument is that the verifying computer and its file integrity are fundamentally vulnerable.

Identity Ambiguity (Which John Robinson is he?)

Identity in PKI is loosely defined, lacking standards for credentials or publicly known unique identifiers. This makes it difficult to tell people apart.

Authority Scope (Is the CA an authority?)

CAs often claim authority over domains they do not actually control, such as "rights" (authorization) or DNS attributes. This confuses authentication authority with authorization authority.

User Exclusion (Is the user part of the design?)

Many PKI processes are hidden from the user, leaving them unable to see or affect what is happening (e.g., a hosted website holding the host's certificate rather than the page's).

Organizational Separation (Was it one CA or CA+RA?)

The separation of the Registration Authority (RA), which handles vetting, from the CA, which issues certificates, can allow for forgery if the binding between these entities is weak.

Authentication Quality (How was the user authenticated?)

Real identification by CAs is arguably poor because they lack good information to work with.

Operational Practices (How secure are the certificate practices?)

Users often fail to use certificates correctly or understand the implications, frequently ignoring expiration and revocation statuses.

Purpose (Why are we using PKI?)

The argument is that PKI was intended to solve the painful problem of authenticating users, but certificates are merely a tool to implement authentication rather than a complete solution. Consequently, PKI has not fully delivered on its promises.