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# AES KEY EXPANSION .pptx

Key expansion

Key expansion

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### AES KEY EXPANSION .pptx

1. 1. AES KEY EXPANSION
2. 2. AES ENCRYPTION AND DECRYPTION DIAGRAM
3. 3. AES KEY EXPANSION The AES algorithm which takes 128 bits (16 bytes) key as input, four-word key as input and produce a linear array of 44 words. (In AES 4 Bytes = 1 Word). Figure describe the steps of key expansion. Figure : 1. Four word round 2. AES Encryption Process
4. 4. AES KEY EXPANSION A four-word round key is acceptable for the initial stage. The initial stage is Add Round Key and each of the 10 rounds of cipher. So, total 11 rounds = 44 words. The key is added into the first four words of the expanded key. Figure : 1. Four word round 2. AES Encryption Process
5. 5. AES KEY EXPANSION • The function g defines the complex and that function consist of some sub function as follow: • Step-1: This function performs the one-byte circular left shift. • Step-2: Using S-box each sub word performs a byte substitution. • Step-3: Finally result of Rot word and step 2 is XORed with the round constant called as Rcon[Round]. Figure : Function g
6. 6. AES KEY EXPANSION • The function g defines the complex and that function consist of some sub function as follow: • Step-1: This function performs the one-byte circular left shift. • Step-2: Using S-box each sub word performs a byte substitution. • Step-3: Finally result of Rot word and step 2 is XORed with the round constant called as Rconst[j]. Figure : STEP-1 W3 Left Shift AF 7F 7F 67 67 98 98 AF W0 w1 w2 w3 0F 47 0C AF 15 D9 B7 7F 71 E8 AD 67 C9 59 D6 98
7. 7. AES KEY EXPANSION Figure : STEP-2 Left Shift 7F 67 98 AF
8. 8. AES KEY EXPANSION Figure : STEP-2 Left Shift S-box 7F 67 98 AF ROW COLUMN
9. 9. AES KEY EXPANSION Figure : STEP-2 Left Shift S-box 7F 67 98 AF ROW COLUMN
10. 10. AES KEY EXPANSION Figure : STEP-2 Left Shift S-box 7F D2 67 98 AF ROW COLUMN
11. 11. AES KEY EXPANSION Figure : STEP-2 Left Shift S-box 7F D2 67 98 AF
12. 12. AES KEY EXPANSION Figure : STEP-2 Left Shift S-box 7F D2 67 85 98 AF
13. 13. AES KEY EXPANSION Figure : STEP-2 Left Shift S-box 7F D2 67 85 98 46 AF
14. 14. AES KEY EXPANSION Figure : STEP-2 Left Shift S-box 7F D2 67 85 98 46 AF 79
15. 15. AES KEY EXPANSION • The function g defines the complex and that function consist of some sub function as follow: • Step-1: This function performs the one-byte circular left shift. • Step-2: Using S-box each sub word performs a byte substitution. • Step-3: Finally result of Rot word and step 2 is XORed with the round constant called as Rcon[Round].
16. 16. AES KEY EXPANSION w0 w1 w2 w3 0F 47 0C AF 15 D9 B7 7F 71 E8 AD 67 C9 59 D6 98 Left Shift (Step-1) S-box (Step-2) 7F D2 67 85 98 46 AF 79 S-box (Step-2) D2 85 46 79 Rcon(Round) 01 00 00 00 w0 0F 15 71 C9 W4 DC 90 37 B0 Step-3: Finally result of Rot word and step 2 is XORed with the round constant called as Rcon[Round].
17. 17. AES KEY EXPANSION w0 w1 w2 w3 w4 w5 w6 w7 0F 47 0C AF DC 9B 15 D9 B7 7F 90 49 71 E8 AD 67 37 DF C9 59 D6 98 B0 E9
18. 18. AES KEY EXPANSION w0 w1 w2 w3 w4 w5 w6 w7 0F 47 0C AF DC 9B 97 15 D9 B7 7F 90 49 FE 71 E8 AD 67 37 DF 72 C9 59 D6 98 B0 E9 3F
19. 19. AES KEY EXPANSION w0 w1 w2 w3 w4 w5 w6 w7 0F 47 0C AF DC 9B 97 38 15 D9 B7 7F 90 49 FE 81 71 E8 AD 67 37 DF 72 15 C9 59 D6 98 B0 E9 3F A7
20. 20. AES EXAMPLE
21. 21. AES EXAMPLE Initial Round Round 1 Round 2 Round 3 Round 4 Round 5 Round 6 Round 7 Round 8
22. 22. AES EXAMPLE
23. 23. AES EXAMPLE