Decryption Algorithms Characterization

Decryption Algorithms Characterization Project ECE 526 spring 2007 Ravimohan Boggula,Rajesh reddy Bandala Southern Illinois University Carbondale

Goal • The goal of this project is to evaluate the processing and energy requirement for two different decryption algorithms.

Introduction • In order to maintain information security and integration across the internet researchers have developed a process named cryptography • CRYPTOGRAPHY is an algorithmic process of converting a plain text or clear text message to a cipher text or cipher message based on an algorithm that both the sender and receiver know, so that the cipher text message can be returned to its original, plain text form. • The act of converting a plain text message to its cipher text form is called enciphering. Reversing that act (i.e., cipher text form to plain text message) is deciphering.

Introduction… • A key is simply a parameter to the algorithm that allows the encryption and decryption process to occur • cryptographic techniques are divided into two classes: symmetric and asymmetric (also called public/private) key cryptography • In symmetric key algorithms encryption key == decryption key • In asymmetric key algorithms encryption key! == decryption key

Introduction…

Introduction… • Symmetric-key algorithms are generally much less computationally intensive than asymmetric key algorithms. In practice, this means that a quality asymmetric key algorithm is hundreds or thousands of times slower than a quality symmetric key algorithm

Data Encryption Standard (DES) • DES encrypts and decrypts data in 64-bit blocks, using a 64-bit key (although the effective key strength is only 56 bits, as explained below). It takes a 64-bit block of plaintext as input and outputs a 64-bit block of ciphertext. Since it always operates on blocks of equal size and it uses both permutations and substitutions in the algorithm, DES is both a block cipher and a product cipher. • DES has 16 rounds, meaning the main algorithm is repeated 16 times to produce the ciphertext. It has been found that the number of rounds is exponentially proportional to the amount of time required to find a key using a brute-force attack. So as the number of rounds increases, the security of the algorithm increases exponentially

Structure of DES

Disadvantages of DES • DES is now considered to be insecure for many applications. This is chiefly due to the 56-bit key size being too small; DES keys have been broken in less than 24 hours. There are also some analytical results which demonstrate theoretical weaknesses in the cipher, although they are infeasible to mount in practice. The algorithm is believed to be practically secure in the form of Triple DES, although there are theoretical attacks. In recent years, the cipher has been superseded by the Advanced Encryption Standard (AES).

Advanced Encryption Standard • Uses 128bits,192bits and 256bits,instead of 56 bits • The AES specifies three key sizes: 128, 192 and 256 bits. In decimal terms, this means that there are approximately: • 3.4 x 1038 possible 128-bit keys; • 6.2 x 1057 possible 192-bit keys; and • 1.1 x 1077 possible 256-bit keys. • In comparison, DES keys are 56 bits long, which means there are approximately 7.2 x 1016 possible DES keys. Thus, there are on the order of 1021 times more AES 128-bit keys than DES 56-bit key

Approach • Hardware approach is difficult to implement as it requires loads of time. • Using a software approach: Rindeal and serpent algorithms

Brief Description • Rijndael is an iterated block cipher with a variable block length and a variable key length. The block length and the key length can be independently specified to 128, 192 or 256 bits. • Serpent is a 32-round SP-network operating on four 32-bit words, thus giving a block size of 128 bits. All values used in the cipher are represented as bitstreams. • Serpent encrypts a 128-bit plaintext P to a 128-bit ciphertext C in 32 rounds under the control of 33 128-bit subkeys ^K0; : : : ; ^K32. The user key length is variable,

Methodology • Using wattch tool we have to evaluate the processing and energy requirement for two different decryption algorithms. • “WATTCH” is an architectural simulator that estimates CPU power consumption. The power estimates are based on a suite of parametrizable power models for different hardware structures and on per-cycle resource usage counts generated through cycle level simulation. The power models have been integrated into the “Simple Scalar” architectural simulator.

Expected results • The expected results include what is the relationship of energy requirement/processing cost with encryption key length and file size.

Summary • Cryptography is an algorithimic process of converting a plain text to a cipher text. • The act of converting a plain text in to cipher text is Encryption. • And the act of converting the cipher text back to original text is Decryption. • We basically use two kinds of key algorithms Syymetric and Assymetric.

References • http://herongyang.com/crypto (cryptographic tutorials) • http://fp.gladman.plus.com/cryptography_technology/index.htm • http://en.wikipedia.org/wiki/data_encryption_standard • http://en.wikipedia.org/wiki/advanced_encryption_standard • http://csrc.nist.gov/CryptoToolkit/aes/rijndael/Rijndael.pdf • http://www.cl.cam.ac.uk/~rja14/Papers/serpent.pdf

Thank you

Decryption Algorithms Characterization