Содержание
- 2. Chapter 5 –Advanced Encryption Standard "It seems very simple." "It is very simple. But if you
- 3. AES Origins clear a replacement for DES was needed have theoretical attacks that can break it
- 4. The AES Cipher - Rijndael designed by Rijmen-Daemen in Belgium has 128/192/256 bit keys, 128 bit
- 5. AES Encryption Process
- 6. AES Structure data block of 4 columns of 4 bytes is state key is expanded to
- 7. AES Structure
- 8. Some Comments on AES an iterative rather than Feistel cipher key expanded into array of 32-bit
- 9. Substitute Bytes a simple substitution of each byte uses one table of 16x16 bytes containing a
- 10. Substitute Bytes
- 11. Substitute Bytes Example
- 12. Shift Rows a circular byte shift in each each 1st row is unchanged 2nd row does
- 13. Shift Rows
- 14. Mix Columns each column is processed separately each byte is replaced by a value dependent on
- 15. Mix Columns
- 16. Mix Columns Example
- 17. AES Arithmetic uses arithmetic in the finite field GF(28) with irreducible polynomial m(x) = x8 +
- 18. Mix Columns can express each col as 4 equations to derive each new byte in col
- 19. Add Round Key XOR state with 128-bits of the round key again processed by column (though
- 20. Add Round Key
- 21. AES Round
- 22. AES Key Expansion takes 128-bit (16-byte) key and expands into array of 44/52/60 32-bit words start
- 23. AES Key Expansion
- 24. Key Expansion Rationale designed to resist known attacks design criteria included knowing part key insufficient to
- 25. AES Example Key Expansion
- 26. AES Example Encryption
- 27. AES Example Avalanche
- 28. AES Decryption AES decryption is not identical to encryption since steps done in reverse but can
- 29. AES Decryption
- 30. Implementation Aspects can efficiently implement on 8-bit CPU byte substitution works on bytes using a table
- 31. Implementation Aspects can efficiently implement on 32-bit CPU redefine steps to use 32-bit words can precompute
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