Discuss the limitations of a KDC system in modern communication

A Key Distribution Center (KDC) system, while effective for symmetric key distribution, faces several limitations in modern communication environments:

• Single Point of Failure: The KDC operates as a central point for key generation and distribution. Its unavailability, due to attack or failure, prevents all secure connection establishments for the entire system, creating a critical vulnerability.
• Scalability Challenges: A growing number of communicating entities can cause the KDC to become a bottleneck. Each secure session needs KDC interaction, which increases load and can degrade performance. Centralized management of many keys and users becomes complex and resource-intensive.
• Trust Requirement: All parties must trust the KDC to generate, store, and distribute keys securely. If the KDC is compromised, an attacker controls all session keys, undermining system-wide communication security.
• Latency and Overhead: Establishing a secure session through a KDC involves multiple exchanges between the client, server, and the KDC to obtain session keys. For example, the Kerberos protocol requires several steps. This process adds network latency and communication overhead, which is unsuitable for dynamic or real-time communication.
• No Non-repudiation for Symmetric Keys: KDCs primarily use symmetric keys. These keys provide confidentiality and integrity, but they do not inherently offer non-repudiation. It is difficult to prove who sent a message when two parties share the same symmetric key. Public Key Infrastructure (PKI) provides non-repudiation through digital signatures, a feature not native to KDC systems.