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Block cipher modes of operation 15 Electronic codebook (ECB) The simplest of the encryption modes is the electronic codebook (ECB) mode. The message is divided into blocks and each block is encrypted separately. The disadvantage of this method is that identical plaintext blocks are encrypted into identical ciphertext blocks; thus, it does not hide data patterns well. In some senses, it doesn't provide serious message confidentiality, and it is not recommended for use in cryptographic protocols at all. A striking example of the degree to which ECB can leave plaintext data patterns in the ciphertext is shown below; a pixel-map version of the image on the left was encrypted with ECB mode to create the center image, versus a non-ECB mode for the right image. Original Encrypted using ECB mode Modes other than ECB result in pseudo-randomness The image on the right is how the image might appear encrypted with CBC, CTR or any of the other more secure modes—indistinguishable <strong>from</strong> random noise. Note that the random appearance of the image on the right does not
Block cipher modes of operation 16 ensure that the image has been securely encrypted; many kinds of insecure encryption have been developed which would produce output just as 'random-looking'. ECB mode can also make protocols without integrity protection even more susceptible to replay attacks, since each block gets decrypted in exactly the same way. For example, the Phantasy Star Online: Blue Burst online video game uses Blowfish in ECB mode. Before the key exchange system was cracked leading to even easier methods, cheaters repeated encrypted "monster killed" message packets, each an encrypted Blowfish block, to illegitimately gain experience points quickly. Cipher-block chaining (CBC) Cipher-block chaining (CBC) mode of operation was invented by IBM in 1976. [12] In CBC mode, each block of plaintext is XORed with the previous ciphertext block before being encrypted. This way, each ciphertext block is dependent on all plaintext blocks processed up to that point. Also, to make each message unique, an initialization vector must be used in the first block. If the first block has index 1, the mathematical formula for CBC encryption is while the mathematical formula for CBC decryption is CBC has been the most commonly used mode of operation. Its main drawbacks are that encryption is sequential (i.e., it cannot be parallelized), and that the message must be padded to a multiple of the cipher block size. One way to handle this last issue is through the method known as ciphertext stealing. Note that a one-bit change in a plaintext or IV affects all following ciphertext blocks.
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Page 3 and 4: Article Licenses License 180
Page 5 and 6: Advanced Encryption Standard 2 is a
Page 7 and 8: Advanced Encryption Standard 4 The
Page 9 and 10: Advanced Encryption Standard 6 Know
Page 11 and 12: Advanced Encryption Standard 8 Test
Page 13 and 14: Block cipher 10 Block cipher In cry
Page 15 and 16: Block cipher 12 Block ciphers and o
Page 17: Block cipher modes of operation 14
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Page 27 and 28: Certificate authority 24 Certificat
Page 29 and 30: Certificate authority 26 Security T
Page 31 and 32: CMAC 28 The CMAC tag generation pro
Page 33 and 34: Cryptographic hash function 30 resi
Page 35 and 36: Cryptographic hash function 32 func
Page 37 and 38: Cryptographic hash function 34 Algo
Page 39 and 40: DiffieHellman key exchange 36 The s
Page 41 and 42: DiffieHellman key exchange 38 3. Bo
Page 43 and 44: DiffieHellman key exchange 40 Upon
Page 45 and 46: DiffieHellman key exchange 42 • C
Page 47 and 48: Digital signature 44 every paramete
Page 49 and 50: Digital signature 46 implemented. I
Page 51 and 52: Digital signature 48 authority). Fo
Page 53 and 54: Digital Signature Algorithm 50 Digi
Page 55 and 56: Digital Signature Algorithm 52 Sens
Page 57 and 58: HMAC 54 Implementation The followin
Page 59 and 60: HMAC 56 External links • FIPS PUB
Page 61 and 62: HTTP Secure 58 Browser integration
Page 63 and 64: HTTP Secure 60 From an architectura
Page 65 and 66: IPsec 62 IPsec Internet Protocol Se
Page 67 and 68: IPsec 64 operates directly on top o
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IPsec 66 Cryptographic algorithms C
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IPsec 68 External links • All IET
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Kerberos (protocol) 70 Kerberos (pr
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Kerberos (protocol) 72 Client Authe
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Kerberos (protocol) 74 External lin
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Message authentication code 76 Mess
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Message authentication code 78 Exte
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NeedhamSchroeder protocol 80 S resp
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Pretty Good Privacy 82 Pretty Good
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Pretty Good Privacy 84 Security qua
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Pretty Good Privacy 86 PGP 3 and fo
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Pretty Good Privacy 88 based on sec
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Public key certificate 90 Public ke
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Public key certificate 92 (b) ensur
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Public key certificate 94 Usefulnes
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Public key infrastructure 96 As tim
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Public key infrastructure 98 Extern
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Public-key cryptography 100 In cont
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Public-key cryptography 102 To achi
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Public-key cryptography 104 using t
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Public-key cryptography 106 Spreadi
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Public-key cryptography 108 Externa
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RSA (algorithm) 110 The RSA algorit
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RSA (algorithm) 112 A working examp
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RSA (algorithm) 114 Signing message
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RSA (algorithm) 116 Side-channel an
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RSA (algorithm) 118 • The PKCS #1
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S/MIME 120 administrative overhead
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Secure Electronic Transaction 122 T
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Secure Shell 124 Usage SSH is typic
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Secure Shell 126 • RFC 4462, Gene
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Secure Shell 128 ability to multipl
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Security service (telecommunication
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Security service (telecommunication
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SHA-1 134 SHA-1 SHA-1 General Desig
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SHA-1 136 Applications SHA-1 forms
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SHA-1 138 At the Rump Session of CR
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SHA-1 140 a = temp Add this chunk's
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SHA-1 142 • Xiaoyun Wang, Yiqun L
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Stream cipher 144 Types of stream c
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Stream cipher 146 Filter generator
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Stream cipher 148 SNOW Pre-2003 Ver
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Symmetric-key algorithm 150 Key gen
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Transport Layer Security 152 TLS 1.
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Transport Layer Security 154 • SS
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Transport Layer Security 156 • Fi
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Transport Layer Security 158 Length
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Transport Layer Security 160 layer
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Transport Layer Security 162 Suppor
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Transport Layer Security 164 • RF
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Transport Layer Security 166 Extern
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X.509 168 Extensions informing a sp
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X.509 170 00:d3:a4:50:6e:c8:ff:56:6
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X.509 172 Exploits • MD2-based ce
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X.509 174 External links • ITU-T
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Article Sources and Contributors 17
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Article Sources and Contributors 17
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License 180 License Creative Common
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