08-05-2012, 05:27 PM
Advanced Encryption Standard
AES.ppt (Size: 252 KB / Downloads: 56)
Advanced Encryption Standard
Adopted by National Institute of Standards and Technology (NIST) on May 26, 2002.
AES is a simple design, a high speed algorithm, with low memory costs.
AES is a symmetric block cipher.
The same key is used to encrypt and decrypt the message.
The plain text and the cipher text are the same size.
Security
Assuming that one could build a machine that could recover a DES key in a second (i.e., try 255 keys per second), then it would take that machine approximately 149 thousand-billion (149 trillion) years to crack a 128-bit AES key. To put that into perspective, the universe is believed to be less than 20 billion years old.
AES Algorithm - MixColumns
This with shift rows provides diffusion
The columns are considered polynomials over GF(28) and multiplied modulo x4+1 with a(x) where a(x) = {03}x3 + {01}x2 + {01}x + {02} NOTE: x4+1 is relatively prime to a(x)
a’j (aj*a(x))mod(x4+1)
This can also be written as matrix multiplication.
Types of Side Channel Attacks
Timing Attacks – Watches movement of data in and out of the CPU or memory.
It is difficult to retrieve an array element in a time that is not dependent on the index value.
Power Attacks – Watches power consumption by CPU or memory.
Changing one bit requires considerably less power than changing all bits in a byte.
AES.ppt (Size: 252 KB / Downloads: 56)
Advanced Encryption Standard
Adopted by National Institute of Standards and Technology (NIST) on May 26, 2002.
AES is a simple design, a high speed algorithm, with low memory costs.
AES is a symmetric block cipher.
The same key is used to encrypt and decrypt the message.
The plain text and the cipher text are the same size.
Security
Assuming that one could build a machine that could recover a DES key in a second (i.e., try 255 keys per second), then it would take that machine approximately 149 thousand-billion (149 trillion) years to crack a 128-bit AES key. To put that into perspective, the universe is believed to be less than 20 billion years old.
AES Algorithm - MixColumns
This with shift rows provides diffusion
The columns are considered polynomials over GF(28) and multiplied modulo x4+1 with a(x) where a(x) = {03}x3 + {01}x2 + {01}x + {02} NOTE: x4+1 is relatively prime to a(x)
a’j (aj*a(x))mod(x4+1)
This can also be written as matrix multiplication.
Types of Side Channel Attacks
Timing Attacks – Watches movement of data in and out of the CPU or memory.
It is difficult to retrieve an array element in a time that is not dependent on the index value.
Power Attacks – Watches power consumption by CPU or memory.
Changing one bit requires considerably less power than changing all bits in a byte.