AES ENCRYPTION
Kevin Orr
JT Schratz
OVERVIEW
• History
• Algorithm
• Uses
• Brute Force Attack
HISTORY
•
Before AES, the Data Encryption Standard (DES) became the federal standard in 1977
•
DES uses a 56-bit key
•
By the late 1990s, however, it was possible to break DES in a matter of several days
•
In January 1997, NIST announced a competition for the successor to DES
•
NIST – National Institute of Standards and Technology
•
The selected the winner was the Rijndael algorithm in October 2000
•
Belgian cryptograhers Joan Daemen and Vincent Rijmen
•
Formally known as AES – Advanced Encryption Standard
ALGORITHM
10 cycles of repetition for 128-bit keys.
12 cycles of repetition for 192-bit keys.
14 cycles of repetition for 256-bit keys.
ALGORITHM STEPS - SUB BYTES
• each byte in the state matrix is replaced with a SubByte using an 8bit substitution box
• bij = S(aij)
SHIFT ROWS
•
Cyclically shifts the bytes in each row by a certain offset
•
The number of places each byte is shifted differs for each row
MIX COLUMNS
•
Each column is multiplied by the known matrix. For the 128-bit key it is
ADD ROUND KEY
•
Each byte of the state is combined with a byte of the round subkey using the XOR operation
USES
•
Government Standard
• AES is standardized as Federal Information Processing Standard 197 (FIPS 197) by NIST
• AES is sufficient to protect classified information up to the SECRET level.
• TOP SECRET information will require use of either the 192 or 256 key lengths.
•
Industry
• SSL / TLS
• SSH
• WinZip
• BitLocker
• Mozilla Thunderbird
• Skype
BRUTE FORCE ATTACK
•
Supercomputer: K Computer (Japan, 2011)
•
Speed: 10.51 Pentaflops= 10.51 x
1015 Flops [Flops = Floating point
operations per second]
•
Flops required per combination = 1000
•
Combination checks per second = (10.51 x
1015) / 1000 = 10.51 x 1012
•
Seconds in a Year = 31536000
•
No. of Years to crack AES with 128-bit Key
= (3.4 x 1038) / [(10.51 x 1012) x 31536000]
= (0.323 x 1026)/31536000
= 1.02 x 1018 years
= 1 billion billion years
CONCLUSION
•
AES has been around for about 12 years and is still a very strong type of encryption
•
Only uses four transformations to create the encryption
•
Many programs today that have a need for encryption often use AES due to its strength
•
The attempted attacks focus on weaknesses or characteristics in specific implementations
called “side channel attacks” and not on the algorithm itself
•
So far it is uncrackable
SOURCES
•
http://luxsci.com/blog/256-bit-aes-encryption-for-ssl-and-tls-maximal-security.html
•
http://www.technewsworld.com/story/70437.html
•
http://www.eetimes.com/design/embedded-internet-design/4372428/How-secure-is-AESagainst-brute-force-attacks-
•
http://en.wikipedia.org/wiki/Advanced_Encryption_Standard
QUESTIONS