International Journal of Advance Engineering and Research Development

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1 Scientific Journal of Impact Factor (SJIF): 4.72 e-issn (O): p-issn (P): International Journal of Advance Engineering and Research Development Volume 4, Issue 5, May-17 Comparaitive Analysis of Symmetric Key Algorithms: DES, AES and Blowfish for Audio Encryption and Decryption Manju Bala 1, Pankaj Kumari 2, Ankush Sharma 3 1 computer science and engineering, Career Point University, Hamirpur(H.P) 2 computer science and engineering, Career Point University, Hamirpur(H.P) 3 computer science and engineering, Career Point University, Hamirpur(H.P) Abstract Cryptography is a method of storing and transmitting data in a particular form so that only those for whom it is intended can read and process it. It is an art and science of transforming messages so as to make them secure and immune to attacks. Cryptography, then, not only protects data from theft or alteration, but can also be used for user authentication. Data that can be read and understood without any special measures is called plaintext or cleartext. The method of disguising plaintext in such a way as to hide its substance is called encryption. Encrypting plaintext results in unreadable gibberish called ciphertext. The process of reverting ciphertext to its original plaintext is called decryption. This research work provides the comparison between four symmetric and asymmetric key cryptographic techniques, namely as DES, AES and Blowfish algorithms in terms of time and security by using Audio simulation. The tool used for the present work is NetBeans IDE It observed that Blowfish algorithms took least time for simulation of encryption and decryption. Keywords- Cryptography, DES, AES, Blowfish and Audio encryption. 1. INTRODUCTION Cryptography, which translates as "secret writing," refers to the science of concealing the meaning of data so only specified parties understand a transmission's contents. Cryptography deals with the actual securing of digital data. It refers to the design of mechanisms based on mathematical algorithms that provide fundamental information security service. Data Security is a challenging issue of data communications today that touches many areas including secure communication channel, strong data encryption technique and trusted third party to maintain the database. The conventional methods of encryption can only maintain the data security [1]. A. Cryptography Many encryption algorithms are widely available and used in information security. They can be categorized into Symmetric (private) and Asymmetric (public) keys encryption. In Symmetric keys encryption or secret key encryption, only one key is used to encrypt and decrypt data. In Asymmetric keys, two keys are used; private and public keys[2]. Figure 1. Basic diagram of All rights Reserved 1048

2 B.Categories of Cryptography Symmetric key (also called secret-key) cryptography algorithms. Asymmetric key (also called public-key) cryptography algorithms Symmetric Key cryptography A secret key, which can be a number, a word, or just a string of random letters, is applied to the text of a message to change the content in a particular way. This might be as simple as shifting each letter by a number of places in the alphabet. As long as both sender and recipient know the secret key, they can encrypt and decrypt all messages that use this key[4]. The popular symmetric cryptographic algorithms include, AES, Blowfish, RC5, DES, 3DES and IDEA. The sender uses this key and an encryption algorithm to encrypt data; the receiver uses the same key and the corresponding decryption. Asymmetric Key cryptography Figure 2. Symmetric Key Cryptography Asymmetric key encryption is the technique, in which the different keys are for the encryption and the decryption process. One key is public (published) and second is kept private. They are also called as the public key encryption[8]. If the lock/encryption key is first published then the system enables private communication from the public to the unlocking key's user. If the unlock/decryption key is the one published then the system serves as a signature verifier of documents locked by the owner of the private key. Public key methods are important because they can be used for transmitting encryption keys or other data securely even when the both the users have no opportunity to agree on a secret key in private Algorithm. The keys used in public-key encryption algorithms are usually much longer that improves the security of the data being All rights Reserved 1049

3 Figure 3. Asymmetric Key Cryptography Symmetric algorithms Data Encryption Standard (DES) Advanced Encryption Standard (AES) Blowfish Algorithm II.METHODOLOGY Data Encryption Standard (DES) DES (Data Encryption Standard) algorithm purpose is to provide a standard method for protecting sensitive commercial and unclassified data. In this same key used for encryption and decryption process. DES algorithm consists of the following steps: i. Encryption 1. DES accepts an input of 64-bit long plaintext and 56-bitkey (8 bits of parity) and produce output of 64 bit block. 2. The plaintext block has to shift the bits around. 3. The 8 parity bits are removed from the key by subjecting the key to its Key Permutation. 4. The plaintext and key will processed by following i. The key is split into two 28 halves ii. Each half of the key is shifted (rotated) by one or two bits, depending on the round. iii. The halves are recombined and subject to a compression permutation to reduce the key from 56 bits to 48 bits. This compressed keys used to encrypt this round s plaintext block. iv. The rotated key halves from step 2 are used in next round. v. The data block is split into two 32-bit halves. vi. One half is subject to an expansion permutation to increase its size to 48 bits. vii.output of step 6 is exclusive-or ed with the 48-bit compressed key from step 3. viii. Output of step 7 is fed into an S-box, which substitutes key bits and reduces the 48-bit block back down to 32-bits. ix. Output of step 8 is subject to a P-box to permute the bits. x. The output from the P-box is exclusive-or ed with other half of the data block. k. The two data halves are swapped and become the next round s input[7]. Advanced Encryption Standard (AES) Advanced Encryption Standard (AES) algorithm not only for security but also for great speed. Both hardware and software implementation are faster All rights Reserved 1050

4 New encryption standard recommended by NIST to replace DES. Encrypts data blocks of 128 bits in 10, 12 and 14 round depending on key size as shown in Figure 3.2. It can be implemented on various platforms specially in small devices[31]. It is carefully tested for many security applications. i. Algorithm Steps: These steps used to encrypt 128-bit block 1. The set of round keys from the cipher key. 2. Initialize state array and add the initial round key to the starting state array. 3. Perform round = 1 to 9 : Execute Usual Round. 4. Execute Final Round. 5. Corresponding cipher text chunk output of Final Round Step ii. Usual Round : Execute the following operations which are described above. 1. Sub Bytes 2. Shift Rows 3. Mix Columns 4. Add Round Key, using K(round) iii. Final Round: Execute the following operations which are described above. 1. Sub Bytes 2. Shift Rows 3. Add Round Key, using K(10) iv. Encryption : Each round consists of the following four steps: 1. Sub Bytes : The first transformation, Sub Bytes, is used at the encryption site. To substitute a byte, we interpret the byte as two hexadecimal digits. 2. Shift Rows : In the encryption, the transformation is called Shift Rows. 3. Mix Columns : The Mix Columns transformation operates at the column level; it transforms each column of the state to a new column. 4. Add Round Key: Add Round Key precedes one column at a time. Add Round Key adds a round key word with each state column matrix; the operation in Add Round Key is matrix addition. The last step consists of XO Ring the output of the previous three steps with four words from the key schedule. And the last round for encryption does not involve the Mix columns step. v. Decryption: Decryption involves reversing all the steps taken in encryption using inverse functions like a) Inverse shift rows, b) Inverse substitute bytes, c) Add round key, and d) Inverse mix columns. The third step consists of XO Ring the output of the previous two steps with four words from the key schedule. And the last round for decryption does not involve the Inverse mix columns step[7]. Blowfish Algorithm This algorithm consists of two parts: Key-expansion part: In Key expansion, a key of at most 448 bits is being converted into several subkeys arrays totaling 4168 bytes. Data- encryption part: In Data encryption, 16-round Feistel network is used. Each round consists of a key dependent permutation, data-dependent substitution and a key. All operations are XORs and additions on 32-bit words. The only additional operations are four indexed array data lookups per round. Blowfish uses a large number of subkeys during its execution. These keys are computed before data encryption or decryption[34]. The P-array consists of 18 subkeys (32 bit): P1, P2,..., P18. There are four S-boxes (32 bit) with 256 entries each: S1,0, S1,1,..., S1,255; S2,0, S2,1,..,, S2,255; S3,0, S3,1,..., S3,255; S4,0, S4,1,..,, S4,255. Encryption Blowfish has 16 rounds. The input is a 64-bit data element, x. Divide x into two 32-bit halves: xl, xr. Then, for i = 1 to 16: xl = xl XOR Pi xr = F(xL) XOR xr Swap xl and xr After the sixteenth round, swap xl and xr again to undo the last swap. Then, xl = xl XOR P17 and xr = xr XOR P18. Finally, recombine xl & xr to get the cipher All rights Reserved 1051

5 Timing (ms) Evaluation Parameters International Journal of Advance Engineering and Research Development (IJAERD) III. EXPERIMENTATION AND RESULTS Performance of encryption algorithm is evaluated considering the following parameters. Encryption Time The encryption time is considered the time that an encryption algorithm takes to produces an encrypted Audio (cipher) from original Audio. Comparisons analyses of the results of the selected different encryption scheme are performed. Image Size (KB) Table 1. Encryption Time using DES, AES and Blowfish Algorithms Encryption Time in milliseconds DES AES Blowfish Evaluation of encryption time: The encryption simulation was performed on DES, AES and Blowfish algorithms had been carried on NetBeans IDE The encryption simulation is probably the most fundamental type of cryptographic analysis that can be performed on the algorithms under study. This simulation is simple and standardized. In this work, the encryption simulation values are obtained for various algorithms, are shown in Figureure given below: ENCRYPTION TIME COMPARISON DES AES BLOWFISH Audio Size(KB) Figure 3.1 Shows the comparison of encryption timing in DES, AES, Blowfish algorithm and the encryption time of the Blowfish algorithm is lesser than AES and DES algorithm. Decryption Time The decryption time is considered the time that a decryption algorithm takes to produces original Audio from encrypted Audio All rights Reserved 1052

6 Timing(ms) International Journal of Advance Engineering and Research Development (IJAERD) Image Size (KB) Table 2. Decryption Time using DES, AES and Blowfish Algorithms Decryption Time in milliseconds DES AES Blowfish Evaluation of decryption time: - The decryption simulation was performed on DES, AES and Blowfish algorithms had been carried on NetBeans IDE The decryption simulation is probably the most fundamental type of cryptographic analysis that can be performed on the algorithms under study. This simulation is simple and standardized. In this work, the decryption simulation values are obtained for various algorithms, are shown in Figureure given below: DECRYPTION TIMING COMPARISON DES Algorithn AES Algorithm 30 Blowfish Algorithm Audio Size(KB) Figure 3.2 Shows the comparison of decryption timing in DES, AES, Blowfish algorithm and the decryption time of the Blowfish algorithm is lesser than DES algorithm. IV.CONCLUSION In cryptography, encryption and decryption algorithms plays important role in network security. In our research work, we analyzed the performance of existing encryption techniques like DES, AES,Blowfish and RSA algorithms. Based on the Audio Size used and the experimental result it was concluded that Blowfish algorithm consumes least encryption time and DES consume maximum encryption time. We also observed that Decryption of Blowfish and AES algorithms is better than DES algorithm. From our research work, it concluded that Blowfish algorithm is better than AES, DES,, Blowfish and RSA All rights Reserved 1053

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