Internet Security - Dang Thanh Binh's Page

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SYMMETRIC BLOCK CIPHERS 71 Thus, the 16-th round decryption process is accomplished counting from the bottomup. In a similar fashion, the rest of the decryption processes are summarised in the following table. Table for decryption blocks (Ri,Li), 15 ≤ i ≤ 0 i RI Li 15 F0d35530 0765cf74 14 F04bf1ad f0d35530 13 6ff2ef60 f04bf1ad 12 b6c73726 6ff2ef60 11 56a0e201 b6c73726 10 d0b10423 56a0e201 9 ec6d1ab8 d0b10423 8 6bc34499 ec6d1ab8 7 8e6f6798 6bc34499 6 c1fe0f05 8e6f6798 5 a6f29581 c1fe0f05 4 61125d5d a6f29581 3 e0e7a039 61125d5d 2 5d189730 e0e7a039 1 5cd9b326 5d189730 0 4713b8f4 5cd9b326 The preoutput block is (R0||L0) = 4713b8f45cd9b326. Using Table 3.8 (IP −1 ), the plaintext is recovered as X = 785ac3a4bd0fe12d. 3.1.5 Triple DES Triple DES is popular in <strong>Internet</strong>-based applications, including PGP and S/MIME. The possible vulnerability of DES to a brute-force attack brings us to find an alternative algorithm. Triple DES is a widely accepted approach which uses multiple encryption with DES and multiple keys, as shown in Figure 3.5. The three-key triple DES is the preferred alternative, whose effective key length is 168 bits. Triple DES with two keys (K1 = K3, K2) is a relatively popular alternative to DES. But triple DES with three keys (K1, K2, K3) is preferred, as it results in a great increase in cryptographic strength. However, this alternative raises the cost of the known-plaintext attack to 2 168 , which is beyond what is practical. Referring to Figure 3.5, the ciphertext C is produced as C = EK3[DK2[EK1(P)]] The sender encrypts with the first key K1, then decrypts with the second key K2, and finally encrypts with the third key K3. Decryption requires that the keys are applied in reverse order: P = DK1[EK2[DK3(C)]]
72 INTERNET SECURITY P P K1 K2 K3 E D D (a) Encryption K1 K2 K3 E (b) Decryption Figure 3.5 Triple DES encryption/decryption. The receiver decrypts with the third key K3, then encrypts with the second key K2, and finally decrypts with the first key K1. This process is sometimes known as Encrypt- Decrypt-Encrypt (EDE) mode. Example 3.6 Using Figure 3.5, the triple DES computation is considered here. Given three keys: K1 = 0x260b152f31b51c68 K2 = 0x321f0d61a773b558 K3 = 0x519b7331bf104ce3 and the plaintext P = 0x403da8a295d3fed9 The 16-round keys corresponding to each given key K1, K2 and K3 are computed as shown below. Round K1 K2 K3 1 000ced9158c9 5a1ec4b60e98 03e4ee7c63c8 2 588490792e94 710c318334c6 8486dd46ac65 3 54882eb9409b c5a8b4ec83a5 575a226a8ddc 4 a2a006077207 96a696124ecf aab9e009d59b 5 280e26b621e4 7e16225e9191 98664f4f5421 6 e03038a08bc7 ea906c836569 615718ca496c 7 84867056a693 88c25e6abb00 4499e580db9c E D C
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TEAMFLY
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Internet Security
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Copyright © 2003 John Wiley & Sons
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vi CONTENTS 2.3 World Wide Web 47 2
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viii CONTENTS 5.6 The Elliptic Curv
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x CONTENTS 10.2.5 De-militarised Zo
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Preface The Internet is global in s
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PREFACE xv Policy Approval Authorit
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PREFACE xvii classified into three
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1 Internetworking and Layered Model
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INTERNETWORKING AND LAYERED MODELS
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Layer No. 7 6 5 4 3 2 1 OSI Layer A
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2 TCP/IP Suite and Internet Stack P
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TCP/IP SUITE AND INTERNET STACK PRO
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TCP/IP SUITE AND INTERNET STACK PRO
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Page 46 and 47: Class A Class B Class C Class D Cla
Page 50 and 51: H Host H TCP/IP SUITE AND INTERNET
Page 64 and 65: Bits IP header TCP/IP SUITE AND INT
Page 78 and 79: 3 Symmetric Block Ciphers This chap
Page 80 and 81: S-boxes L i−1 S 1 L i SYMMETRIC B
Page 82 and 83: K 1 48 bits K 2 48 bits K 16 48 bit
Page 84 and 85: Table 3.4 Initial permutation (IP)
Page 86 and 87: SYMMETRIC BLOCK CIPHERS 65 Table 3.
Page 88 and 89: SYMMETRIC BLOCK CIPHERS 67 This 48-
Page 90 and 91: SYMMETRIC BLOCK CIPHERS 69 The 48-b
Page 94 and 95: SYMMETRIC BLOCK CIPHERS 73 Round K1
Page 96 and 97: SYMMETRIC BLOCK CIPHERS 75 Example
Page 98 and 99: 64-bit plaintext X 1 X 2 X 3 X 4 Ro
Page 102 and 103: SYMMETRIC BLOCK CIPHERS 81 The outp
Page 104 and 105: SYMMETRIC BLOCK CIPHERS 83 the corr
Page 108 and 109: SYMMETRIC BLOCK CIPHERS 87 of S and
Page 110 and 111: Step 3 i = j = 0; A = B = 0; SYMMET
Page 112 and 113: 3.3.3 Encryption SYMMETRIC BLOCK CI
Page 114 and 115: A SYMMETRIC BLOCK CIPHERS 93 A B
Page 116 and 117: 3.4 RC6 Algorithm SYMMETRIC BLOCK C
Page 118 and 119: Mixing in the secret key S A = B =
Page 120 and 121: Magic constants: Pw = b7e15163 Qw =
Page 122 and 123: A = ((A − S[2i]) >>> u) ⊕ t } D
Page 124 and 125: Converting the secret key from byte
Page 126 and 127: The final decrypted plaintext is: b
Page 128 and 129: Thus, the final decrypted plaintext
Page 130 and 131: Multiplication SYMMETRIC BLOCK CIPH
Page 132 and 133: where c0 = a0b0 c1 = a1b0 ⊕ a0b1
Page 134 and 135: Rcon[2] = [x 1 , {00}, {00}, {00}]
Page 136 and 137: Table 3.16 AES key expansion i Temp
Page 138 and 139: SYMMETRIC BLOCK CIPHERS 117 ShiftRo
Page 140 and 141: Start of round After SubByte SYMMET
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SYMMETRIC BLOCK CIPHERS 121 Figure
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4 Hash Function, Message Digest and
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M = 64 bits C 0 = 28 bits D 0 = 28
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HASH FUNCTION, MESSAGE DIGEST AND H
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⊕ : Bit-by-bit XORing of 16-bit s
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P(Ω 1 )
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K r : Concatenation IP : Initial pe
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a b c d HASH FUNCTION, MESSAGE DIGE
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H2 = 98badcfe H3 = 10325476 H4 = c3
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opad 160 bits (SHA-1) 128 bits (MD5
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5 Asymmetric Public-key Cryptosyste
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User A Generate secret random integ
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ASYMMETRIC PUBLIC-KEY CRYPTOSYSTEMS
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Message m −1 E p q ASYMMETRIC PUB
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Message m −1 User A A′ private
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To decipher the message m, first co
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a q ≡ 1(modp) a ASYMMETRIC PUBLIC
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Receiver: (verifying) Compute: w
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� y2 − y1 x3 = ASYMMETRIC PUBLI
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The square of the integers in Z ∗
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and y3 = x2 1 + � x1 + y1 = α 12
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6 Public-key Infrastructure This ch
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PUBLIC-KEY INFRASTRUCTURE 203 LDAP
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Session key DES Plaintext m One-way
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PUBLIC-KEY INFRASTRUCTURE 207 Let u
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PUBLIC-KEY INFRASTRUCTURE 209 sent
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Publication of PAA’s public key G
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PUBLIC-KEY INFRASTRUCTURE 213 • P
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Carry out identification and authen
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PUBLIC-KEY INFRASTRUCTURE 217 With
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PUBLIC-KEY INFRASTRUCTURE 219 The s
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6.4.4 X.500 Distinguished Naming PU
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PUBLIC-KEY INFRASTRUCTURE 223 certi
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PUBLIC-KEY INFRASTRUCTURE 225 • I
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Certificate fields v1 = v2 = v3 (fo
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PUBLIC-KEY INFRASTRUCTURE 229 CRL s
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Subject directory attributes extens
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PUBLIC-KEY INFRASTRUCTURE 233 the s
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PUBLIC-KEY INFRASTRUCTURE 235 • S
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PUBLIC-KEY INFRASTRUCTURE 237 not h
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6.7.1 Basic Path Validation PUBLIC-
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PUBLIC-KEY INFRASTRUCTURE 241 It is
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244 INTERNET SECURITY The set of se
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246 INTERNET SECURITY • Key manag
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248 INTERNET SECURITY 7.1.3 Hashed
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250 INTERNET SECURITY A B C D IV 67
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252 INTERNET SECURITY Next header (
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254 INTERNET SECURITY IPv4 IPv4 IPv
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256 INTERNET SECURITY within a 32-b
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258 INTERNET SECURITY addresses, wh
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260 INTERNET SECURITY If authentica
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262 INTERNET SECURITY 1 bit Next pa
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264 INTERNET SECURITY The Situation
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266 INTERNET SECURITY The Identific
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268 INTERNET SECURITY The Hash Data
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270 INTERNET SECURITY The Domain of
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272 INTERNET SECURITY to the exchan
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274 INTERNET SECURITY When a Key Ex
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276 INTERNET SECURITY When a Notifi
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278 INTERNET SECURITY SSL Handshake
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280 INTERNET SECURITY SSL record he
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282 INTERNET SECURITY SSLCompressed
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284 INTERNET SECURITY • bad-certi
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286 INTERNET SECURITY - Random: Thi
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288 INTERNET SECURITY Note that Dis
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290 INTERNET SECURITY The finished
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292 INTERNET SECURITY key_block = M
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294 INTERNET SECURITY opad 160 bits
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296 INTERNET SECURITY - A B C D IV
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298 INTERNET SECURITY The PRF is th
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300 INTERNET SECURITY HMAC SHA1(S2,
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302 INTERNET SECURITY 8.3.4 Certifi
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9 Electronic Mail Security: PGP, S/
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ELECTRONIC MAIL SECURITY: PGP, S/MI
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Message packet M T FN H(M) ELECTRON
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Definition of multipart/encrypted:
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From: myrhee@tsp.snu.ac.kr To: kiis
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SignatureAlgorithmIdentifier ELECTR
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340 INTERNET SECURITY conform to a
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342 INTERNET SECURITY existing on a
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344 INTERNET SECURITY 10.2.7 VPN So
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346 INTERNET SECURITY Table 10.1 Te
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348 INTERNET SECURITY Table 10.3 SM
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350 INTERNET SECURITY Outside host
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352 INTERNET SECURITY Internet Pack
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11 SET for E-commerce Transactions
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11.2 SET System Participants SET FO
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SET FOR E-COMMERCE TRANSACTIONS 359
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Example 11.2 Message Integrity Chec
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User A 0x135af247c613e815 Message d
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E KSC (CAC) + E KSC (MD) D CAC MD V
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H MD D CRs K pg M’s cert E K#5 (C
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380 INTERNET SECURITY DS Dual Signa
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382 INTERNET SECURITY SA Security A
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384 INTERNET SECURITY 17. Borman, D
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386 INTERNET SECURITY 60. Harkins,
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388 INTERNET SECURITY 106. Metzger,
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390 INTERNET SECURITY 163. Wijnen,
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392 INDEX Authentication Header 243
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394 INDEX delete payload 269, 275,
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396 INDEX HTML tag 49 ending tag 49
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398 INDEX Java 48, 49 Joint Photogr
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400 INDEX packet filter 339, 341, 3
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402 INDEX secure payment processing
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404 INDEX transform # field 264, 27
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