Threats on CBC Operation

• Modification of cipher text blocks.
• Changing has predictable effect on .
  • However, it also changes piin an unpredictable manner
• If the receiver is known to ignore pithen such attack is possible.
  • Possible safeguard is to attach a checksum (such as CRC) to the message before encryption.

PKI

• PKI Operations:
• Encryption, Decryption of short messages
• Digital signatures
• Authentication
• RSA: Uses modular exponents to make it computationally infeasible to recover message without key.
• Provided the message is carefully crafted. Keys are carefully selected.

Security Mechanism

• Confidentiality
  • Will an attacker make any sense out of a picked packet?
• Integrity
  • Is the message unaltered?
• Owner Integrity
  • Is the message really from that person?
• Authentication
  • Is it you?