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Network security cs5
The document covers network security concepts focusing on block ciphering, specifically AES (Advanced Encryption Standard) and its significance in security. It details AES structure, including its iterative process, key expansion, and encryption methods, while contrasting it with DES (Data Encryption Standard). The AES is highlighted for its resistance to attacks, speed, and applicability in various commercial platforms.
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Network security cs5
- 1. Network Security CS-5 By: Prof.Ganesh Ingle
- 2. Session 2 objective CS-5Revision Previous Session revision CS -5 Block Ciphering CS -5 Revision of DES,Feistel Cipher Structure CS -5 Confusion and Diffusion Theory CS -5 AES and its importance in security CS-5 Efficient implementation of AES using C and C# demo. SUMMARY
- 3. CS -5 BlockCiphering This functionality is similar to block cipher Only difference is key
- 4. CS -5 BlockCiphering This functionality is similar to block cipher Only difference is key
- 5. CS -5 BlockCiphering This functionality is similar to block cipher Only difference is key And must be reversible
- 6. CS -5 BlockCiphering
- 7. CS -5 BlockCiphering Can any function be used as a block cipher ???
- 8. CS -5 BlockCiphering Block Cipher Algorithms: DES (Explanation done in session two ,refer video lecture Module 7) AES RC6
- 9. 9 CS -5 FeistelCipher Structure 1. PT=2 halves 2. Apply function to right 3. Function can be anything a logical model 4. For function a separate key will be used 5. O/p from 5 is XORed with left 6. O/P of left and right is swapped 7. Process 1 to 7 is a round 8. Number of rounds Block Cipher Design Principles 1.Block Size (10B PT=10B CT) 2.Key size 3.Sub Keys Count 4.Round Function 5.Plain Text in Two equal Halves
- 10. 10 CS -5 Confusionand Diffusion Theory
- 11. 11 CS -5 Confusionand Diffusion Theory
- 12. 12 CS -5 AESand its importance in security AES(Applications in commercial market) Intel and AMD processors include the AES instruction set. Signal Protocol Google Allo (optional) Facebook Messenger (optional) Signal TextSecure WhatsApp Linux kernel's Crypto API, now exposed to userspace DataLocker Uses AES 256-bit CBC and XTS mode hardware encryption BitLocker (part of certain editions of Windows operating systems) 7z ,Amanda Backup,PeaZip,PKZIP,RAR,WinZip,UltraISO Hadoop
- 13. 13 CS -5 AESand its importance in security AES(Advance Encryption Standard): Symmetric Key Block cipher (Same key ???) 128 bit data 128 bit key size 56 bit size key was used in DES vulnerable for the brut force attack Stronger and faster than DES
- 14. 14 CS -5 AESand its importance in security Rounds Key 10 128 12 192 14 256
- 15. 15 CS -5 AESand its importance in security AES Structure: AES Encryption process:
- 16. 16 CS -5 AESand its importance in security AES(Advance Encryption Standard): Considering 10 rounds S1:Input PT=128 bits S2:Pre round transformation ( a key goes here k0) like DES here also we have key expansion block S3:Now starts number of rounds (key is added to each round) It runs up to round n depending upon key size
- 17. 17 CS -5 AESand its importance in security AES(Advance Encryption Standard): designed by Rijmen-Daemen in Belgium has 128/192/256 bit keys, 128 bit data an iterative rather than Feistel cipher processes data as block of 4 columns of 4 bytes operates on entire data block in every round designed to have: resistance against known attacks speed and code compactness on many CPUs design simplicity
- 18. CS -5 AESkey expansion block
- 19. CS -5 AESencryption process S1:Input PT=128 bits S2:Pre round transformation ( a key goes here k0) like DES here also we have key expansion block S3:Now starts number of rounds (key is added to each round) Sub bytes : its matrix of 4x4 (s-boxes) Shift rows (Left shift only) & create new matrix for net step Mix columns : Columns are mixed with some mathematical function Add round key : Bit streams are now XORed with round key This process is repeated till last round Row number Shift left 1 0 2 1 3 2 4 3 Decryption process is exact reverse of this
- 20. 20 CS-5 Efficient implementationof AES. Sub bytes : Wikipedia reference
- 21. CS -5 AESencryption process S box
- 22. CS -5 AESencryption process Substitute Bytes Example
- 23. CS -5 AESencryption process Shift Rows A circular byte shift in each each 1st row is unchanged 2nd row does 1 byte circular shift to left 3rd row does 2 byte circular shift to left 4th row does 3 byte circular shift to left Decrypt inverts using shifts to right Since state is processed by columns, this step permutes bytes between the columns
- 24. CS -5 AESencryption process Shift Rows
- 25. CS -5 AESencryption process Mix Columns each column is processed separately each byte is replaced by a value dependent on all 4 bytes in the column effectively a matrix multiplication in GF(28) using prime poly m(x) =x8+x4+x3+x+1
- 26. CS -5 AESencryption process Mix Columns
- 27. CS -5 AESencryption process AES Arithmetic uses arithmetic in the finite field GF(28) with irreducible polynomial m(x) = x8 + x4 + x3 + x + 1 which is (100011011) or {11b} e.g. {02} • {87} mod {11b} = (1 0000 1110) mod {11b} = (1 0000 1110) xor (1 0001 1011) = (0001 0101)
- 28. CS -5 AESencryption process Add Round Key XOR state with 128-bits of the round key again processed by column (though effectively a series of byte operations) inverse for decryption identical since XOR own inverse, with reversed keys designed to be as simple as possible a form of Vernam cipher on expanded key requires other stages for complexity / security
- 29. CS -5 AESencryption process Add Round Key
- 30. CS -5 AESencryption process Key Expansion takes 128-bit (16-byte) key and expands into array of 44/52/60 32-bit words start by copying key into first 4 words then loop creating words that depend on values in previous & 4 places back in 3 of 4 cases just XOR these together 1st word in 4 has rotate + S-box + XOR round constant on previous, before XOR 4th back
- 31. 31 CS -5 AESand its importance in security
- 32. 32 CS -5 AESand its importance in security Summary an iterative rather than Feistel cipher key expanded into array of 32-bit words four words form round key in each round 4 different stages are used as shown has a simple structure only AddRoundKey uses key AddRoundKey a form of Vernam cipher each stage is easily reversible decryption uses keys in reverse order decryption does recover plaintext final round has only 3 stages
- 33. 33 CS -5 AESand its importance in security
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- 42. CS-5 AES vsDES
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