PGP (Pretty Good Privacy)

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PGP (Pretty Good Privacy)

• Sheila Alston
• Old Dominion University
• November 2, 2005

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What is PGP?

• Secure mail protocol
• Performs encryption and integrity protection on
  files
• Original author Phil Zimmerman
• Guerrilla Freeware
• Generates private key for you
• Uses public key cryptography for personal keys

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How PGP Encryption Works

• User encrypts plaintext using PGP
• PGP compresses the plaintext
• PGP creates a session key, which is a one-time
  secret key
• The secret key works with the plaintext using a
  conventional encryption algorithm to encrypt the
  plaintext
• The end result is ciphertext
• Once data is encrypted the session key is
  encrypted to the recipients public key
• Public key-encrypted session key is transmitted
  along with the encrypted data to the recipient

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How PGP Works
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How PGP Decryption Works

• The recipient's copy of PGP uses their private
  key to recover the session key
• PGP uses the recovered session key to decrypt the
  ciphertext
• The combination of the two encryption methods
  combines the convenience of public key encryption
  with the speed of conventional encryption

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How PGP Decrypts
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Key Distribution

• PGP uses public key cryptography for personal
  keys
• Each user decides which keys to trust
• PGP doesnt require certificates. They are
  optional.
• To send someone mail or to verify their
  signature, you need to know their public key
• People publish their PGP fingerprints on their
  websites, business cards, in their books, etc.

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Private Key

• PGP will generate a private key for you
• You can specify the size of the key
• It prompts you for a password
• Password is converted into a IDEA key by doing
  MD5 message digest
• IDEA key is used to encrypt the private key
• Encryption is done with 64-bit CFB using a random
  IV which is stored with the encrypted private key

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Key Rings

• PGP creates key rings
• Key Rings are data structures that contain. pubic
  keys, information about people and certificates.
• Key Rings can be used as a database of public
  keys.
• There are three levels of trust in PGP none,
  partial, or complete.

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Conclusion

• PGP is used to perform encryption and decryption
  for mail and for integrity protection of files.
• It is capable of accepting different types of
  formatsmessage formats and primitive object
  formats.
• PGP is used to protect our privacy.

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References

• How PGP Works, http//www.pgpi.org/doc/pgpintro/
  
• Network Security Private Communication in a
  Public World, Second Edition, Prentice Hall PTR
• ftp//ftp.pgpi.org/pub/pgp/6.5/docs/english/IntroT
  oCrypto.pdf
• PGP Corporation - Home Page http//www.pgp.com/

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Thank You