信息安全導(dǎo)論(密碼學(xué))期末復(fù)習(xí)

1、2022-2-10Final Review 胡海波胡海波page22022-2-10Final Review 胡海波胡海波page32022-2-10Final Review 胡海波胡海波page42022-2-10Final Review 胡海波胡海波page5Symmetric CryptographyAsymmetric CryptographyCryptographic Hash Function2022-2-10Final Review 胡海波胡海波page6Cryptographic Hash FunctionAsymmetric CryptographySymmetric Cry

2、ptographyDecryptionAlgorithmEncryptionAlgorithm2022-2-10Final Review 胡海波胡海波page7Symmetric CryptographyCryptographic Hash FunctionAsymmetric CryptographyDecryptionAlgorithmEncryptionAlgorithm2022-2-10Final Review 胡海波胡海波page8Symmetric CryptographyCryptographic Hash FunctionAsymmetric CryptographyEncry

3、ptionAlgorithmDecryptionAlgorithm2022-2-10Final Review 胡海波胡海波page9Symmetric CryptographyAsymmetric CryptographyCryptographic Hash FunctionOriginalMessage2022-2-10Final Review 胡海波胡海波page102022-2-10Final Review 胡海波胡海波page11分組密碼分組密碼流密碼流密碼秘鑰管理秘鑰管理2022-2-10Final Review 胡海波胡海波page12S-BoxXORCircular ShiftS

4、wapSplit / CombineP-BoxA P-box (置換盒置換盒) parallels the traditional transposition cipher for characters. It transposes (移動(dòng)移動(dòng)) bits. A straight(直接的直接的) P-box is invertible(可逆的可逆的), but compression and expansion P-boxes are not.e.g.2022-2-10Final Review 胡海波胡海波page13P-BoxXORCircular ShiftSwapSplit / Comb

5、ineS-BoxAn S-box (替換盒替換盒) can be thought of as a miniature(微小的微小的) substitution cipher. An S-box is an m n substitution unit, where m and n are not necessarily the same.e.g.1e.g.2110 11010 012022-2-10Final Review 胡海波胡海波page14P-BoxS-BoxCircular ShiftSwapSplit / CombineXORThe exclusive-or operation is

6、 an important component in most block ciphers. +e.g.2022-2-10Final Review 胡海波胡海波page15P-BoxS-BoxXORSwapSplit / CombineCircular ShiftThe circular shift operation is another component found in some modern block ciphers. e.g.2022-2-10Final Review 胡海波胡海波page16P-BoxS-BoxXORCircular ShiftSplit / CombineSw

7、apThe swap operation is a special case of the circular shift operation where k = n/2. e.g.EncryptionDecryption2022-2-10Final Review 胡海波胡海波page17P-BoxS-BoxXORCircular ShiftSwapSplit / CombineTwo other operations found in some block ciphers are split and combine. e.g.SplitCombineEncryptionDecryption20

8、22-2-10Final Review 胡海波胡海波page182022-2-10Final Review 胡海波胡海波page19DES64bit plaintext64bit ciphertextInitial permutationRound 1Round 2Round 16Final permutation.56bit keyK1K2K16Round-key generator2022-2-10Final Review 胡海波胡海波page202022-2-10Final Review 胡海波胡海波page21Multiple Encryption Triple DES Triple

9、DES with 2 keys C=Ek1(Dk2(Ek1(P) P=Dk1(Ek2(Dk1(P) K1+K2: 112bits C=Ek3(Dk2(Ek1(P) P=Dk1(Ek2(Dk3(C) More secure than DES, but with more cost2022-2-10Final Review 胡海波胡海波page222022-2-10Final Review 胡海波胡海波page231) Byte Substitution2) Shift Rows3) Mix Columns4) Add Round key2022-2-10Final Review 胡海波胡海波pa

10、ge242022-2-10Final Review 胡海波胡海波page252022-2-10Final Review 胡海波胡海波page26CBCCFBOFBCTRECB4The electronic codebook (ECB) mode is the simplest mode of operation.4Each block of plaintext is encoded independently(獨(dú)立獨(dú)立地地) using the same key.2022-2-10Final Review 胡海波胡海波page27ECBCFBOFBCTRCBC4To transmit a le

11、ngthy message, we might employ the so called Cipher Block Chaining (CBC) mode；4In this scheme, the input to the encryption algorithm is the XOR of the current plaintext block and the preceding ciphertext block; the same key is used for each block.4To transmit a lengthy message, we might employ the s

12、o called Cipher Block Chaining (CBC) mode；4In this scheme, the input to the encryption algorithm is the XOR of the current plaintext block and the preceding ciphertext block; the same key is used for each block.2022-2-10Final Review 胡海波胡海波page28ECBCBCOFBCTRCFB2022-2-10Final Review 胡海波胡海波page29ECBCBC

13、CFBCTROFBOutput Feedback Mode is Similar to CFB. Can you find the difference?2022-2-10Final Review 胡海波胡海波page30ECBCBCCFBOFBIn the counter (CTR) mode, there is no feedback. The pseudo-randomness(偽隨機(jī)) in the key stream is achieved using a counter. CTR2022-2-10Final Review 胡海波胡海波page3111001100011011001

14、0100000+plaintextkey streamciphertext2022-2-10Final Review 胡海波胡海波page322022-2-10Final Review 胡海波胡海波page332022-2-10Final Review 胡海波胡海波page34Initialization Initialization is done in two steps:Key Stream GenerationThe keys in the key stream are generated, one by one. 2022-2-10Final Review 胡海波胡海波page35a

15、KbK2022-2-10Final Review 胡海波胡海波page36|1NIDBIDArequestAsKsKIDKENrequestKEba,|11245(|)bKsAEKID2NKs2NfKs62022-2-10Final Review 胡海波胡海波page372022-2-10Final Review 胡海波胡海波page382022-2-10Final Review 胡海波胡海波page39 Global Public ElementsY：YP, Y是是P的素?cái)?shù)根的素?cái)?shù)根P：素?cái)?shù)素?cái)?shù) For AliceSelected private: A, ( AP )Calculate public =YA mod P For BobSelected private B, ( BP ) Calculate public =YB mod P For AliceKey= A mod P For BobKey= B mod P2022-2-10Final Review 胡海波胡海波page40nMCemodnMnMnCMedde