Advanced Encryption Standard (AES) AES Group March 3, 2019 - PowerPoint PPT Presentation

Faculty of Information Engineering and Technology’ Advanced Encryption Standard (AES) AES Group March 3, 2019

Content 1 Introduction Methods AddRoundKey SubBytes ShiftRows MixColumns Key Expansion Conclusion AES Group | The Feather Beamer Theme

Introduction 2 ◮ Internet AES Group | The Feather Beamer Theme

Introduction 3 ◮ What is Encryption? AES Group | The Feather Beamer Theme

Introduction 4 ◮ Idea Of Encryption AES Group | The Feather Beamer Theme

Introduction 5 Types of Encryption: ◮ Blowfish ◮ RSA ◮ 3DES ◮ AES AES Group | The Feather Beamer Theme

Introduction 6 ◮ The National institute of standards and technology and AES: AES Group | The Feather Beamer Theme

Introduction 7 ◮ What is good about AES? AES Group | The Feather Beamer Theme

Methods AddRoundKey 8 LET’S SAY FOR EXAPMLE WE HAVE THE FOLLOWING: AES Group | The Feather Beamer Theme

Methods AddRoundKey 9 ENCRYPTION PROCESS: Figure: Encryption process AES Group | The Feather Beamer Theme

Methods AddRoundKey 10 The previous figure shows the steps of the encryption process, first you get your input array of binary digits and X-OR it with the array of the Cipher key this step is called AddRoundKey Method, then you pass by 4 stages 9 times then you have a final round. Each of the 9 stages consist of the same 4 methods: ◮ AddRoundKey ◮ SubBytes ◮ ShiftRows ◮ MixColumns At Round 1 after passing by the 4 methods, we X-OR it with the Cipher Key again, then at Round 2 we pass by the same 4 methods but here we X-OR the output Round 2 with the Output of Round 1 and so on until Round 9, we keep X-OR-ing with the result of the previous round, whereas Round 10 doesn’t include MixColumns. AES Group | The Feather Beamer Theme

Methods AddRoundKey 11 Figure: Encryption process explained AES Group | The Feather Beamer Theme

Methods AddRoundKey 12 Figure: Encryption process explained AES Group | The Feather Beamer Theme

Methods SubBytes 13 The State: ◮ It is Matrix of size 4x4 ◮ Hexadecimal bits ◮ Digits AES Group | The Feather Beamer Theme

Methods SubBytes 14 ◮ SECOND transformation ◮ Substitute a byte ◮ Using S-Box Figure: SubBytes method AES Group | The Feather Beamer Theme

Methods SubBytes 15 ◮ 16x16 Array ◮ rows and columns indexed by hexadecimal bits array AES Group | The Feather Beamer Theme

Methods SubBytes 16 Figure: S-box AES Group | The Feather Beamer Theme

Methods SubBytes 17 ◮ Two Digits representation ◮ The new byte from S-Box ◮ The content change ◮ No change in arrangement of bytes AES Group | The Feather Beamer Theme

Methods ShiftRows 18 Figure: ShiftRows method AES Group | The Feather Beamer Theme

Methods MixColumns 19 Figure: MixColumns method First result byte is calculated by multiplying 4 elements in the first column of the state by the first 4 elements in the row of multiplication matrix (c) B 1 = ( b 1 ∗ 2 ) xor ( b 2 ∗ 3 ) xor ( b 3 ∗ 1 ) xor ( b 4 ∗ 1 ) (1) Second result byte is calculated by multiplying 4 elements in the first column of the state by the second 4 elements in the row of multiplication matrix (c) AES Group | The Feather Beamer Theme

Methods MixColumns 20 B 2 = ( b 1 ∗ 1 ) xor ( b 2 ∗ 2 ) xor ( b 3 ∗ 3 ) xor ( b 4 ∗ 1 ) (2) Third result byte is calculated by multiplying 4 elements in the first column of the state by the Third 4 elements in the row of multiplication matrix (c) B 3 = ( b 1 ∗ 1 ) xor ( b 2 ∗ 1 ) xor ( b 3 ∗ 2 ) xor ( b 4 ∗ 3 ) (3) Forth result byte is calculated by multiplying 4 elements in the first column of the state by the fourth 4 elements in the row of multiplication matrix (c) B 4 = ( b 1 ∗ 3 ) xor ( b 2 ∗ 1 ) xor ( b 3 ∗ 1 ) xor ( b 4 ∗ 2 ) (4) AES Group | The Feather Beamer Theme

Methods Key Expansion 21 ◮ This phase is crucial because it protects the key from being vulnerable to attacks. ◮ This phase takes place where expansion of the cipher key into 11 partial keys, used in the initial round, the 9 main rounds and the final round. AES Group | The Feather Beamer Theme

Methods Key Expansion 22 ◮ The Process goes as follows: a) Applying the RotWord and SubBytes transformation to the previous word (wi-1). b) Adding (XOR) this result to the word 4 position earlier (wi-4), plus a round constant Rcon. AES Group | The Feather Beamer Theme

Methods Key Expansion 23 Figure: Key expansion method AES Group | The Feather Beamer Theme

Methods Key Expansion 24 Figure: Key expansion method AES Group | The Feather Beamer Theme

Methods Key Expansion 25 Figure: Key expansion method AES Group | The Feather Beamer Theme

Methods Key Expansion 26 Figure: Key expansion method AES Group | The Feather Beamer Theme

Methods Key Expansion 27 ◮ The remaining 32-bit words (wi) are calculated by adding (XOR) the previous word (wi-1) with the word4 positions earlier (wi-4). AES Group | The Feather Beamer Theme Figure: Key expansion method

Methods Key Expansion 28 Figure: Key expansion method AES Group | The Feather Beamer Theme

Conclusion 29 ◮ In Conclusion , AES is a symmetric block cipher algorithm that consists of 4 rounds. ◮ ADDRoundKey in which the cipher key is combined with state using bitwise XOR. ◮ SubBytes where we substitute every byte in the state into the corresponding byte in the ASCII code(S-Box ). ◮ ShiftRows where we shift the bytes in a cyclic manner to the left in each row other than the number 0 row. ◮ MixColumns where multiplication is carried out between each byte of a row by each byte in the state column and the output is XORED to produce 4 new bytes. ◮ And finally , Key expansion where the cipher key is expanded to 11 partial keys used in each round. AES Group | The Feather Beamer Theme

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