International Journal of Computer Applications (0975 – 8887) National Conference on Power Systems & Industrial Automation (NCPSIA 2015) 18 Optimization of Block Cipher with SIMON Shylaja C PG Scholar, VLSI & Embedded System Dept. of Electronics & Communication SJCE,Mysuru. Shreekanth T Assistant Professor Dept. of Electronics & Communication SJCE,Mysuru. ABSTRACT In cryptography, a block cipher is a deterministic algorithm operating on fixed-length groups of bits, called blocks, with an unvarying transformation that is specified by a symmetric key. Block ciphers are important elementary components in the design of many cryptographic protocols, and are widely used to implement encryption of bulk data. A block cipher is a method of encrypting text (to produce cipher text) in which a cryptographic key and algorithm are applied to a block of data (for example, 64 contiguous bits) at once as a group rather than applying it to one bit at a time. The primary purpose of encryption is to protect the confidentiality of digital data stored on computer systems or transmitted via the Internet or other computer networks. A recent promising low-cost alternative of advanced encryption standard (AES) on reconfigurable platforms called the SIMON. It has been implemented as the construction of the round function and the key generation of SIMON, that enables bit-serial hardware architectures which can significantly reduce the cost. Encryption and decryption can be done using the same hardware and also propose the hardware architecture of the smallest block cipher ever published on field-programmable gate arrays (FPGAs) at 128- bit level of security. Keywords AES, SIMON, Block Cipher, Feistel , FPGA. 1. INTRODUCTION Encryption is a part of our day-to-day life, mainly used to anticipate monitoring on our communications like phone calls, Internet, security system associations, making e-business and e-banking achievable and also where ever hiding the information from visible eyes are required. According to the history of advancement, old encryption functions have been broken & reconstructed to new form of encryption functions. Here one type of encryption functions are block ciphers. A block ciphers contains two functions: encryption function and decryption function. The data blocks of bytes with fixed size are processed by Block ciphers. Using a block cipher same key is used for both receiver end and sender ends of the channel. With the utilization of same key to encrypt the plaintext blocks, results in the same cipher text block.At present utilized block cipher is Rinjdael, and that was chosen as the winner of National Institute of Standards and Technology (NIST) supported test for new encryption standard in 2000. After conquering of the Advanced Encryption Standard (AES) challenge, presently Rinjdael cipher is frequently known as AES. With Consideration of a block ciphers are capable of encrypting the data only for fixed-sized blocks; they use the mode of operation with block cipher to encrypt bulk sets of data. Block ciphers can be examined as vital block of the symmetric-key encryption system, relatively being utilized just to encode the messages. The execution of encryption is analytical, particularly on the server side of intelligence, the block ciphers are intended to be quick in hardware and software application. For block ciphers encryption, input is fixed-size plaintext data, which is converted into a same cipher text data. Thus this fixed length data is known as block size. The frequently block sizes utilized in the present block ciphers are 64 bits and 128 bits. 1.1 Overview of Cipher Model An encryption of symmetric type has following 5 factors as depicted in Fig.1 [2]. a) Plaintext: It is a unique message or information which is given as input to the algorithm. b) Encryption algorithm: This performs transformation of plaintext into encrypted data. c) Secret key: This is additionally another data to the algorithm. The key be an independent value. Depending on the secret key it will results the distinctive output used at the time. The algorithm performs transformation rely on upon the key. d) Cipher text: It is a specified output from the algorithm. The results rely upon the plaintext and key. For a particular data, different two cipher texts generated by two different keys. Therefore cipher text is an irregular stream of information & is incomprehensible. Fig.1: An encryption model of symmetric type. The two requirements used for the conventional encryption are: a) Require of strong algorithm such that if the opponent able to access one or more cipher texts would unable to decrypt the plaintext or discover the key for several cipher text is accompanied by the plaintext which generated by every cipher text. b) Receiver and sender should share the key which should be secure fashion. Here the only the key is kept in secure this is possible with symmetric encryption algorithm.