Modified aes algorithm using multiple s boxes

Modified aes algorithm using multiple s boxes

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  1 Modified AES AlgorithmUsing Multiple S-Boxes Instructor: Truong Tuan Anh, PhD S: Chu Xuân Tình - 1870583
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  2 Modified AES AlgorithmUsing Multiple S-Boxes 1. Introduction 2. Advance Encryption Standard (AES) 3. Modified AES Algorithm 4. Avaluation AES - Modifier
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  3 AES - introdution ØIn 2000, the NIST formally adopted the AES encryption algorithm and published it as a federal standard under the designation FIPS-197. Ø It was chosen because of its security, performance, efficiency, implement ability, and low memory requirements. • Rijndael was selected as the AES – Designed by Vincent Rijmen and Joan Daemen in Belgium
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  4 AES - introdution ØThe AES Cipher - Rijndael • An iterative – processes data as block of 4 columns of 4 bytes (128 bits) – operates on entire data block in every round • Rijndael design: – simplicity – has 128/192/256 bit keys, 128 bits data – resistant against known attacks – speed and code compactness on many CPUs • The MixColumn function in the AES algorithm is an important property of the cipher
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  5 AES - introdution ØThe MixColumn function in the AES algorithm is an important property of the cipher ü It provides strength against differential and linear attacks due to the complexity of its mathematical operations. ü Require computational resources in software implementation. ü Replacing the MixColumn function, the speed performance of the AES algorithm will be improved. ü Propose for a modified AES algorithm using multiple S-Boxes.
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  6 AES - Classfication
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  AES - Basic 7 AES Plaintext(128 bits) Ciphertext (128 bits) Key (128-256 bits) AES Conceptual Scheme
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  AES - Basic 8 ØMultiple rounds • Rounds are (almost) identical – First and last round are a little different
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  High Level Description NoMixColumns
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  AES - OverallStructure
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  AES - Cipher
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  AES -128-bit values 12 •Data block viewed as 4-by-4 table of bytes • Represented as 4 by 4 matrix of 8-bit bytes. • Key is expanded to array of 32 bits words 1 byte
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  AES - DataUnit
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  AES - UnitTransformation
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  AES - ChangingPlaintext to State
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  AES -Details ofEach Round
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  AES- SubBytes: ByteSubstitution • A simple substitution of each byte – provide a confusion • Uses one S-box of 16x16 bytes containing a permutation of all 256 8-bit values • Each byte of state is replaced by byte indexed by row (left 4-bits) & column (right 4-bits) – eg. byte {95} is replaced by byte in row 9 column 5 – which has value {2A} • S-box constructed using defined transformation of values in Galois Field- GF(28)
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  AES - SubBytesand InvSubBytes
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  AES - SubBytesOperation • The SubBytes operation involves 16 independent byte- to-byte transformations. • Interpret the byte as two hexadecimal digits xy • SW implementation, use row (x) and column (y) as lookup pointer S1,1 = xy16 x’y’16
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  AES - SubBytesTable • Implement by Table Lookup
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  AES - InvSubBytesTable
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  Sample SubByte Transformation •The SubBytes and InvSubBytes transformations are inverses of each other.
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  AES - ShiftRows •Shifting, which permutes the bytes. • 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 • In the encryption, the transformation is called ShiftRows • In the decryption, the transformation is called InvShiftRows and the shifting is to the right
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  AES - ShiftRowsScheme
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  AES - ShiftRowsand InvShiftRows
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  AES - MixColumns •ShiftRows and MixColumns provide diffusion to the cipher • 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
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  AES -MixClumns Scheme TheMixColumns transformation operates at the column level; it transforms each column of the state to a new column.
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  AES-MixColumn & InvMixColumn
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  AES - AddRoundKey •XOR state with 128-bits of the round key • AddRoundKey proceeds one column at a time. – adds a round key word with each state column matrix – the operation is matrix addition • Inverse for decryption identical – since XOR own inverse, with reversed keys • Designed to be as simple as possible
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  AES - AddRoundKeyScheme
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  AES Round
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  AES Key Scheduling •takes 128-bits (16-bytes) key and expands into array of 44 32-bit words
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  AES -Key ExpansionScheme
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  AES -Key Expansionsubmodule • RotWord performs a one byte circular left shift on a word For example: RotWord[b0,b1,b2,b3] = [b1,b2,b3,b0] • SubWord performs a byte substitution on each byte of input word using the S-box • SubWord(RotWord(temp)) is XORed with RCon[j] – the round constant
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  AES Security • AESwas designed after DES. • Most of the known attacks on DES were already tested on AES. • Brute-Force Attack – AES is definitely more secure than DES due to the larger-size key. • Statistical Attacks – Numerous tests have failed to do statistical analysis of the ciphertext • Differential and Linear Attacks – There are no differential and linear attacks on AES as yet.
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  AES ALGORITHM USINGMULTIPLE S-BOXES vPROPOSED MODIFIED 128-AES ALGORITHM USING MULTIPLE S-BOXES Ø The MixColumns function is perceive to be requiring more computational resources in software implementation as compared to the other functions Ø Propose for a modified version of the 128-AES algorithm using two substitution boxes ü The first S-Box is the Rijndael S-Box ü The second S-Box is constructed using XOR operation and affine transformation
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  AES ALGORITHM USINGMULTIPLE S-BOXES
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  AES - CONSTRUCTIONOF THE NEW S-BOX vThe second S-Box is derived from the original S- Box as designed in the AES ØExclusive OR Operation § each cell in the AES-Rijndael will be XORed with 7F AES-Rijndael[x,y] XOR (7F) § The Key[i] shall be any hexadecimal value between 00 to FF (Table 1. AES- 2SboxXOR7F)
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  AES - CONSTRUCTIONOF THE NEW S-BOX
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  AES - CONSTRUCTIONOF THE NEW S-BOX vThe second S-Box is derived from the original S- Box as designed in the AES ØExclusive OR Operation ØAffine Transform Operation ü After creating the initial values of AES- 2SboxXOR ü Scramble the bits in each byte value, we next apply the following transformation to each bit bi as stored in the initial AES-2SboxXOR7F:
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  AES - CONSTRUCTIONOF THE NEW S-BOX ØAffine Transform Operation ü For the inverse AES-2SboxXOR, the following transformation to each bit was used for bit scrambling:
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  AES - CONSTRUCTIONOF THE NEW S-BOX
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  EVALUATION RESULTS
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  EVALUATION RESULTS
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  EVALUATION RESULTS
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  CONCLUSION üModified AES algorithmusing multiple S-boxes. üWe observed that the speed performance greatly increased in the modified AES algorithm using multiple S-Boxes, while the security side has slightly weakened. üEasily implemented using cheap processors and a minimum amount of memory. üVery efficient 49
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  Referents • [1] NationalInstitute of Standards and Technology, Advanced Encryption Standard, FIPS 197 (2011). • [2] Paper “Modified AES Algorithm Using Multiple S-Boxes” • [3] Wiki & slide & Internet. 50
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  51 Thanks for yourattention!