1. Hybrid Cryptography using symmetric key Encryption Sean Laurel Rex Bashyam, Karthik Shankar, Sai Theja kadiyala and Abdelshakour Abuzneid Department of Electrical Engineering and Computer Engineering, University of Bridgeport, CT. AbstractBackground References Introduction Conclusion and Acknowledgement An Efficient algorithm should provide maximum security with operation in less time the hybrid combination of above mentioned algorithms are more secured and it also provides completion in less time as when combined. We can also implement some other algorithms to improve the security of the system by improving the key length and also by using efficient combination of algorithms in future. Acknowledgement: We would like to thank IEEE, IJCS, Microsoft visual studio and our Professor. Abdel-shakour Abuzneid for his guidance and support that made this project possible Here we discuss about DES, AES and Blowfish algorithms in detail DES: In 1970, NIST and FIPS standards introduced an encryption algorithm for transfer of data in secured way. They fixed some methods to code the input text basically in DES we use 64 bit block size for word and 56 bit key.Generally here, the 64bit word and 56 bit key is mixed to form a 64 bit cipher word, and then the same is repeated for decryption. AES: In 1997 NIST along with FIPS standard formed a new symmetric key algorithm. AES [8] has 64 bit block size. In AES we have 128, 192 and 256 bit key size with 10, 12 and 14 rounds respectively. In AES the data and key is mixed to form a strong key. Blowfish: Blowfish is one of the fastest and flexible symmetric key encryption method, which was introduced in 1993 by NIST standard, which has 64 bit block size and has variable key lengths of 32 to 448 bits which easily adapts in hybrid cryptography. fig.3.AES flow diagram crucial methods are introduced to deploy the majority networks to acquire the required data. Because of the defect of only the single data encryption and the use of famous encryption algorithm, which was not improved in traditional methods of the registration process, a combined encryption algorithm is proposed in this thesis[1- 4]. This proposed algorithm provides new step to avoid shortcomings. We use some famous algorithms to encrypt a data as follows. At first, we create new algorithm in order to provide security issue and time constraint of operation then we combine AES using multiplexing of keys, Improvement in DES key size and blowfish algorithm, then we encrypt data using the proposed algorithm. This can enhance the security and complicates the Encryption. In this paper we provide both the encryption and decryption that supports in real time application and algorithm has a practical value. Index Terms— Hybrid encryption, Advance Encryption Standard (AES), Data Encryption Standard (DES), Blowfish, Key length Encryption is a method of converting plain text to cipher text. Generally lot of secured information’s are transferred using internet services these can be easily retrieved by eavesdroppers in the community system. Encryption is mainly employed in banking, accounting, state and national bureau, military and geographical locations. Generally we have so many encryption algorithms which encrypt data, each encryption algorithm has its own style of formatting plain text to cipher text. The main problem nowadays faced by the network engineers is security, time taken to complete, probability of encrypting the data. The basic idea of increasing key size will improve the security. But the method of implementing in single algorithm will have the same security issue. To avoid this we propose hybrid algorithm (fig.1), which will use three or four encryption methods to generate a new key with more security fig.1. overview of hybrid cryptography We commonly have two types of encryption algorithms (a) symmetric key encryption, (b) Asymmetric key encryption algorithm. Where symmetric key uses a shared key and other algorithm uses private key and public key. Here we analyze three algorithms they are: Data encryption standard (DES), Advanced Encryption Standard (AES), Blowfish Algorithm. Fig.2.Key Expansion in Blowfish An efficient algorithm should provide maximum security with operation in less time the hybrid combination Proposal work 1.Sowmya nag k., h.b.bhuvaneswari, nuthan a.c, “Implementation of advanced encryption Standard-192 bit using multiple keys” ieee transcation,vol 5,pg34-39,2012. 2.Najib A. Kofahil,“Performance evaluation of three Encryption/ decryption algoriithms” ISSN 0-7803-8294-3 IEEE,2014 3.Penchalaiah, N. and Seshadri, R. “Effective Comparison and Evaluation of DES and Rijndael Algorithm (AES)”, International Journal of Computer Science and Engineering, Vol. 02, No. 05, 2010, 1641-1645. 4.Seung-jo han “The improved data encryption standard (des) algorithm”Ieee transaction ISSN 0-7803-3567-8,volume,issue,December 1996. Algorithm and mathematical approach As name suggest hybrid cryptography. Here we combine two or three encryption algorithms to form an strong new encryption algorithm. Here, we considered two main constraints (a) Key length (b) Time to complete operation without error. Firstly, when the length of key increases a common key length to fit all three operations. In this proposal, we used 256 bit as the new key length, which has 128, 96, 32 like AES, DES and blowfish respectively. Here the key is having 3 parts where first 128 bits are allotted for AES algorithm and here we use multiplexing of keys to provide extra safety to keys. AES using multiple keys, where AES uses the 64 bit block of data(fig 4). fig.4. AES using multiple keys Similarly 128 bits are split into two parts. They are taken as k1 and k2 where usually k1 and k2 is directly multiplexed to form 64 bit output which is EXOR’ed with input data, then 64 bit key is split in two halves again then multiplexed, then shift rows, mixing of columns and then round key is produced it is again Moored with data. Similarly 9 rounds are completed in final round except mix columns operation rest is done(fig 3). fig.5. Improved DES using 96 bits The next 96 bits are allotted for DES, In DES the input data 64 bits are expanded and mixed to form 52 bits and 96 bits are split into 2 parts as 84 and 12 bits, where 12 bits are allotted for parity bits the rest 84 bits are altered and complex operation is done The first sub key is fed to main algorithm to mix with data; again we use 7 bit left and right shift operation to complete 16 rounds. The left out 32 bits are encrypted using blowfish algorithm (fig 2 (b)), generally the key size is 32 bits, where the 32 bits are separated in 4 equal parts as(8*4)=32 bits. Each 8 bit is sent to s box to form a new 32 bit using substitution. Here the operation is as follows K i =K 1 mod K 2 K b =K i XOR K 3 K i =K b mod K 4 Where K i is the final key produced in a single round Each time the same operation is done to form a new round key and this is sent to main algorithm, where this main algorithm has data expansion operation. The data expansion in blowfish algorithm follows fiestel network which has 18 rounds [4]. Every time a new key forms it will be appended with data to form the encrypted data(fig 2 (b)). Thus after forming the new encrypted key (long key, combination of DES, AES and Blowfish). The similar operation is done in vice versa to get the original text fig.6. Timing Diagram for Hybrid Cryptography crucial methods are introduced to deploy the majority networks to acquire the required data. Because of the defect of only the single data encryption and the use of famous encryption algorithm, which was not improved in traditional methods of the registration process, a combined encryption algorithm is proposed in this thesis[1- 4]. This proposed algorithm provides new step to avoid shortcomings. We use some famous algorithms to encrypt a data as follows. At first, we create new algorithm in order to provide security issue and time constraint of operation then we combine AES using multiplexing of keys, Improvement in DES key size and blowfish algorithm, then we encrypt data using the proposed algorithm. This can enhance the security and complicates the Encryption. In this paper we provide both the encryption and decryption that supports in real time application and algorithm has a practical value. Index Terms— Hybrid encryption, Advance Encryption Standard (AES), Data Encryption Standard (DES), Blowfish, Key length