CyberCode Academy

Course 17 - Computer Network Security Protocols And Techniques | Episode 7: Understanding Pretty Good Privacy (PGP) for Secure Email

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In this lesson, you’ll learn about:
  • What PGP is and where it operates in the network stack
  • How PGP secures email confidentiality and authenticity
  • The three-part structure of a PGP-secured message
  • How session keys, public keys, and digital signatures work together
  • The cryptographic algorithms supported by PGP
Introduction Pretty Good Privacy (PGP) is an application-layer security protocol designed to protect email communications. It combines symmetric encryption, public key cryptography, and digital signatures to ensure that messages remain confidential, authentic, and tamper-proof during transmission. How PGP Secures an Email PGP divides a protected email into three main components, each serving a specific security purpose. Part One: Session Key Protection
  • Contains the session key and the symmetric encryption algorithm used
  • The session key is a temporary, randomly generated key
  • This entire part is encrypted using the recipient’s public key
  • Ensures that only the intended recipient can recover the session key
Part Two: Encrypted Content and Digital Signature
  • Contains the actual email message
  • The message is encrypted using the session key
  • Includes a digital signature created by:
    • Hashing the message to produce a digest
    • Encrypting the digest with the sender’s private key
  • Provides:
    • Integrity (message was not altered)
    • Authentication (message truly came from the sender)
    • Non-repudiation
  • Also specifies the hashing and encryption algorithms used
Part Three: PGP Header
  • Contains protocol-related metadata
  • Helps the recipient’s PGP software correctly process the message
Cryptographic Algorithms Supported by PGP PGP is flexible and supports multiple cryptographic standards:
  • Public Key Algorithms:
    • RSA
    • DSS
  • Hash Functions:
    • MD5
    • SHA-1
    • RIPEMD
  • Symmetric Encryption Algorithms:
    • AES
    • Triple DES (3DES)
Key Takeaways
  • PGP operates at the application layer
  • Uses hybrid encryption for efficiency and security
  • Public keys protect the session key, not the message directly
  • Digital signatures ensure authenticity and integrity
  • Widely used for secure email communication


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CyberCode AcademyBy CyberCode Academy