.c om cu u du o ng th an co ng SYMMETRIC CIPHERS ADVANCED ENCRYPTION STANDARD CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om Contents AES Origins 2) AES Structure 3) AES Key Expansion 4) An AES Example 5) AES Decryption cu u du o ng th an co ng 1) CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om cu u du o ng th an co ng AES Origins CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om AES Origins  Clear a replacement for DES was needed have theoretical attacks that can co ng break it have demonstrated exhaustive key search attacks cu u du o ng th an  Can use Triple-DES – but slow, has small blocks CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om The AES Cipher - Rijndael ng  Designed by Rijmen-Daemen in Belgium co  has 128/192/256 bit keys, 128 bit data th an  Designed to have: du o ng  resistance against known attacks cu  design simplicity u  speed and code compactness on many CPUs CuuDuongThanCong.com https://fb.com/tailieudientucntt cu u du o ng th an co ng c om AES Encryption Process CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om cu u du o ng th an co ng AES Structure CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om AES Structure ng  Plaintext block size: 128 bits co  Key length:16, 24, or 32 bytes (128, 192, or 256 bits) cu u du o ng depending on the key length th an  The algorithm is referred to as AES-128, AES-192, or AES-256, CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om ng co an th ng du o u cu CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om Detailed Structure du o ng th an co ng  128-bit block as consisting of a × matrix of bytes, arranged as follows: cu AES u  The × matrix of bytes shown above is referred to as the state array in CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om MixColumns Transformation cu u du o ng th an co ng  the individual additions and multiplications are performed in GF(28) CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om d Add Round Key Transformation cu u du o ng th an co ng  XOR state with 128-bits of the round key CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om ng co an th ng du o u cu CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om cu u du o ng th an co ng Aes Key Expansion CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om Key Expansion Algorithm  Input a four-word (16-byte) key and produces a linear array of 44 words co ng (176 bytes) th an  This is sufficient to provide a four-word round key for the initial Add cu u du o ng Round Key stage and each of the 10 rounds of the cipher CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om Key Expansion Algorithm ng  w[i] = w[i-1] ⨁w[i-4] an th the warray is a multiple of 4: co  For a word whose position in du o u cu used (g) ng a more complex function is CuuDuongThanCong.com https://fb.com/tailieudientucntt co ng c om Key Expansion Algorithm th an  For example, suppose that the round key for round is du o ng EA D2 73 21 B5 8D BA D2 31 2B F5 60 7F 8D 29 2F u Then the first bytes (first column) of the round key for round are cu calculated as follows: CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om cu u du o ng th an co ng AN AES EXAMPLE CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om  For this example, the plaintext is a hexadecimal palindrome.The plaintext, cu u du o ng th an co ng key, and resulting ciphertext are CuuDuongThanCong.com https://fb.com/tailieudientucntt cu u du o ng th an co ng c om AES Decryption CuuDuongThanCong.com https://fb.com/tailieudientucntt cu u du o ng th an co ng c om Inverse Substitute Bytes CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om Inverse Shift Row Transformation  The inverse shift row transformation, called InvShiftRows, performs the co ng circular shifts in the opposite direction for each of the last three rows, with cu u du o ng th an a 1-byte circular right shift for the second row, and so on CuuDuongThanCong.com https://fb.com/tailieudientucntt cu u du o ng th an co ng c om Inverse Mix Column Transformation CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om Inverse Add Round Key Transformation  The inverse add round key transformation is identical to the forward add cu u du o ng th an co ng round key transformation, because the XOR operation is its own inverse CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om ng co an th ng du o u cu CuuDuongThanCong.com https://fb.com/tailieudientucntt ... AES Origins 2) AES Structure 3) AES Key Expansion 4) An AES Example 5) AES Decryption cu u du o ng th an co ng 1) CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om cu u du o ng th an. ..  The algorithm is referred to as AES- 128, AES- 192, or AES- 256 , CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om ng co an th ng du o u cu CuuDuongThanCong.com https://fb.com/tailieudientucntt... CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om ng co an th ng du o u cu CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om cu u du o ng th an co ng Aes Key Expansion CuuDuongThanCong.com