McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Security PART VII

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Security Topics

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Chapters Chapter 29 Cryptography Chapter 30 Message Authentication, User Authentication, and Key Management Chapter 31 Security Protocols in The Internet

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Chapter 29 Cryptography

McGraw-Hill©The McGraw-Hill Companies, Inc., Introduction IntroductiontoCryptography

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 29.1 Cryptography components

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 29.2 Encryption and decryption

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 In cryptography, the encryption/decryption algorithms are public; the keys are secret. Note:

McGraw-Hill©The McGraw-Hill Companies, Inc., Symmetric-Key Cryptography Traditional Cipher Block Cipher Operation Modes

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 29.3 Symmetric-key cryptography

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 In symmetric-key cryptography, the same key is used by the sender (for encryption) and the receiver (for decryption). The key is shared. Note:

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 In symmetric-key cryptography, the same key is used in both directions. Note:

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Symmetric-key cryptography is often used for long messages. Note:

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 29.4 Caesar cipher

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 29.5 Example of monoalphabetic substitution

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 In monoalphabetic substitution, the relationship between a character in the plaintext to the character in the ciphertext is always one-to-one. Note:

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 29.6 Vigenere cipher

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 In polyalphabetic substitution, the relationship between a character in the plaintext and a character in the ciphertext is one-to-many. Note:

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 29.7 Transpositional cipher

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 29.8 Block cipher

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 29.9 P-box

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure S-box

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure Product block

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure DES

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure General scheme of DES

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure Iteration block

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure Triple DES

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 The DES cipher uses the same concept as the Caesar cipher, but the encryption/decryption algorithm is much more complex due to the sixteen 48-bit keys derived from a 56-bit key. Note:

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure ECB mode

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure CBC mode

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure CFM

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure CSM

McGraw-Hill©The McGraw-Hill Companies, Inc., Public-Key Cryptography RSA Choosing Public and Private Keys

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure Public-key cryptography

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Public-key algorithms are more efficient for short messages. Note:

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure RSA