Overview
This lecture explains public key infrastructure (PKI), covering both symmetric and asymmetric encryption, key management, and the importance of digital certificates in organizations.
Public Key Infrastructure (PKI)
- PKI refers to the policies, procedures, hardware, and software for managing digital certificates.
- PKI handles the creation, distribution, management, storage, and revocation of digital certificates.
- A certificate authority (CA) is central to PKI, associating certificates with users or devices to establish trust.
- PKI is fundamental for verifying identities before granting access.
Symmetric Encryption
- Symmetric encryption uses the same secret key for both encryption and decryption.
- The secret key must be securely shared among all parties who need to decrypt the data.
- Managing keys becomes complex as the number of users grows.
- Symmetric encryption is fast and efficient but can be difficult to scale.
- It is also called secret key algorithm or shared secret.
Asymmetric Encryption
- Asymmetric encryption uses two mathematically related keys: a public key (shared) and a private key (kept secret).
- Data encrypted with the public key can only be decrypted with the private key.
- The private key cannot be derived from the public key.
- Applications like PGP/GPG require users to generate a public/private key pair.
- The public key can be distributed openly, while the private key should be protected, often with a password.
Example: Encrypted Communication
- Alice generates a public/private key pair and distributes her public key.
- Bob uses Alice's public key to encrypt a message (plain text), creating cipher text.
- Only Alice can decrypt the message using her private key, ensuring confidentiality.
Key Management and Escrow
- In large organizations, managing many key pairs requires planning and possibly third-party key escrow solutions.
- Key escrow allows organizations to retain private keys for data recovery if users leave or data access is required.
- Key escrow is sometimes mandatory to maintain data availability.
Key Terms & Definitions
- Public Key Infrastructure (PKI) — The framework for managing digital certificates and keys.
- Certificate Authority (CA) — An entity that issues and manages digital certificates.
- Symmetric Encryption — Encryption using a single secret key for both encryption and decryption.
- Asymmetric Encryption — Encryption using a pair of related keys: public and private.
- Key Escrow — Storing private keys with a trusted third party for backup or recovery.
Action Items / Next Steps
- Review the differences between symmetric and asymmetric encryption.
- Understand the role and responsibilities of a certificate authority in PKI.
- Explore how key management and escrow policies impact organizational security.