Key Management

1
Key Management
2
Session and Interchange Keys

• Key management distribution of cryptographic
  keys, mechanisms used to bind an identity to a
  key, and the generation, maintenance, and
  revoking of such keys
• Solves problem of propagating authentication
• Interchange key cryptographic key associated
  with a principal to a communication
• Session key - cryptographic key associated with
  the communication

3
Key Exchange

• Goal is two allow two parties to communicate
  secretly using a shared cryptographic key
• Key cannot be transmitted in the clear (must be
  encipher when sent or derived without an exchange
  of data used to derive the key)
• Sender and receiver may decide to trust a third
  party
• Cryptosystems and protocols are publicly known.
  The only secret data is the keys involved.

4
Cryptographic Key Infrastructures

• Certificate- token that binds an identity to a
  cryptographic key
• X.509 Directory Authentication Framework
  defines certificate formats and certification
  validation (see security notes for details)
• Certification authority (CA) entity that issues
  certificates
• PGP (Pretty Good Privacy) enchipherment program
  widely used to provide privacy for electronic
  mail (see web link to www.pgp.org)

5
Storing and Revoking Keys

• If stored in a file, easy to compromise, even if
  enchiphered
• Store on one or more smart cards (ROM)

6
Digital Signatures

• Digital signatures authenticates both the
  origin and content of a message
• Uses public key cryptography
• Provides nonrepudiation
• RSA Digital Signature (some problems)
• El Gamal Digital Signature