Analysis And Improvement On IDEA Subkey Extendable Algorithm

With the rapid development of world economy and rapid technological progress,our lifebecoming increasingly dependent on network in everyday life,through the network to handlepersonal affairs, to search for all kinds of information, to understand the latest information ofthe world for commercial activities and on-line payment system. If this information directlytransmits in the channel without processed, that will cause the disclosure of personal propertyand privacy information.So it is necessary to solve this problem. Only by solving this issue,people can rest assured that participate in network activities, thereby promoting economicdevelopment. Network development not only brings economic and life opportunities and funto us, but also brings challenges.Cryptography provides a open channel transmission method of private information toensure that only recipient can read the correct information. This is the most basic function incryptography, it also can confirm the sender and the recipient and verify the integrity of theinformation. Cryptography comes from the Greek root of "hide" and "information"combinations, the main object of study is cryptographic techniques,simple password has beenappear more than four thousand years, with the different development of network technology,but cryptography has only recently been a rapid development.Cryptography can be divided into two major areas depending on the research content,cryptography and cryptanalysis. Cryptography discuss the design and theory of the encryptionalgorithm mainly on the research of algorithm performance, to ensure that the algorithm canencrypt information efficiently and the confidentiality of information;Cryptanalysis isstudying the reliability of known encrypt algorithm,analyzing algorithm performance is mostimportant part of cryptanalysis.cryptanalysis speculates plaintext depend onciphertextanalyzed to study the unknown decryption key, plaintext ciphertext speculation withunknown decryption key.This paper first introduces the standard IDEA algorithm base, introduces the detailthrough the process of the algorithm,thereby know the weak key issue of IDEA algorithm.IDEA weak key problem is caused by the subkey expansion algorithm,so weak key attackshave emerged,such as differential attack for reducing rounds of the IDEA algorithm.So this paper is aimed at improving the IDEA subkey extendable algorithm.IDEA (International Data Encryption Algorithm.) was proposed by Xuejia Lai andJ.Massey in1990.At that time, it is referred to PES(Proposed Encryption Standard). The authorimproved the PES by enhancing the ability of the algorithm against differential analysis in1992, saying that the algorithm for the IPES, also known as of IDEA. The algorithm is a blockencryption algorithm, encrypted data packet length is64bit, the key length is128bit,it isbased on the different algebraic groups on the hybrid operation algorithm. This makes thealgorithm easy to implement in hardware and software. IDEA was presented after a largenumber of targeted reviews to prove its good resistance, and has been applied to the relevantproducts. IDEA is the better algorithm to replace the DES algorithm and it used by PGP, sothat the algorithm is widely used now.The IDEA subkey extendable algorithm was improved.The pseudo-random sequence wasproposed to implement the randomness of subkey.The attacker can’t analyse the position of theinitial key in subkeys.The attackers can’t ensure the position of the weak key.In the process ofgenerating subkey using pseudo-random sequence, the linear probing rescattering wasimported to avoid the performance that different frequency of initial key causing new weakkey.Testable attacking experiment and analysis of security and efficiency shows that suchimprovement can enhance the safety and efficiency.