Digital Certificates and Trust in IT Security

Introduction to Digital Certificates

• A digital certificate is a file containing both a public key and a digital signature.
• Functions like a digital ID card but with more capabilities, particularly in providing authentication and trust.

Trust in IT Security

• Trust is a critical characteristic in IT security, ensuring the user accessing a system is who they claim to be.
• Digital certificates help establish trust by having a Certificate Authority (CA) digitally sign the certificate.

Methods to Provide Trust

• Centralized Certificate Authority: A CA signs the certificate, and if the CA trusts the entity, so should you.
• Web of Trust: Multiple individuals sign each other's certificates, creating a network of trust.
• Internal Certificate Authorities: Useful within organizations to create and manage their own certificates.

Digital Certificate Format

• Websites use a standardized format known as X.509 certificates.
• Digital certificates store a wealth of information including:
  • Serial number, version, and signature algorithm.
  • Issuer of the certificate, holder's name, public key, etc.

Trust and the Root of Trust

• Root of Trust: A foundational trust entity, which can be hardware, software, or firmware-based.
• The browser checks certificates against a list of trusted CAs.
• Hundreds of CAs can issue certificates trusted by browsers.

Certificate Purchasing

• Purchasing a certificate involves buying the validation process that ensures authenticity.
• The CA verifies the certificate requester controls the domain or service in question.

Internal Certificate Authorities

• Organizations can set up their own CA for internal services.
• Involves installing CA software, and distributing the CA certificate to all internal computers.
• Mirrors the processes of external CAs.

Wildcard Certificates

• A Wildcard certificate allows a single certificate to work for multiple subdomains (e.g., *.example.com).
• Useful for organizations needing to secure many devices under the same domain.*

Certificate Revocation

• Certificates can be revoked if a server is decommissioned or compromised.
• Certificate Revocation List (CRL): A list of revoked certificates maintained by the CA.
• Heartbleed Example: Highlighted the need for revocation after a major security flaw in OpenSSL.

Checking Certificate Revocation

• Browsers can check revocation status using CRLs or the Online Certificate Status Protocol (OCSP).
• OCSP Stapling: Embeds certificate status in SSL handshake, improving efficiency.
• Ensures up-to-date information without downloading large CRLs.

Conclusion

• Digital certificates are crucial for secure communications and trust establishment in IT systems.
• Understanding and managing digital certificates, including their issuance, revocation, and verification, is essential for cybersecurity.