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International Journal of Emerging Trends & Technology in Computer Science (IJETTCS)
Web Site: www.ijettcs.org Email: editor@ijettcs.org, editorijettcs@gmail.com
Volume 3, Issue 3, May-June 2014 ISSN 2278-6856
International Journal of Emerging Trends & Technology in Computer Science (IJETTCS) Web Site: www.ijettcs.org Email: editor@ijettcs.org, editorijettcs@gmail.com Volume 3, Issue 3, May-June 2014 ISSN 2278-6856 An Optimized Technique for Secure Data Over Cloud OS R. H. Sakr1, F. Omara2, O. Nomir3 1,3 Mansoura University,Faculty of Computers and Information, 2 Cairo University, Faculty of Computer Science and Information Abstract: The cloud computing becomes morepopular, and IaaS (Infrastructure as a service). A cloud computing especially with large companies as they share resources in a system must make a copy of all its clients’ information cost effective way. It provides an advanced computing and store it on other devices. These copies are enabling to platform in which the users can access computing services on the central server to access backup machines to retrieve demand anytime and anywhere.It integrates, optimizes and the data. Also, the Cloud Service Provider (CSP) provides computing ability, aiming to simplify the clients’ maintains database and applications for the users on a computincomputingg jobs by the way of renting resources remote server and provides independence of accessing and services. Due to this increasingdemand for more cloud services, there is an ever growing threat of security becoming them from any place through a network [9]. a major issue. The Advanced Encryption Standard (AES), In spite of Cloud computing advantages in cost reduction, and the Rivest-Shamir-Adleman (RSA) algorithms are the resource sharing, and time saving for new service main popular encryption schemes that guarantee deployment, most data and software are resided on the confidentiality and authenticity. According to the work in this Internet. This would introduce some new challenges for paper, a hybrid encryption algorithm based on these two the system, especially security and privacy. Because each security algorithms is introduced and implemented on a cloud application may use resources from multiple servers, and platform called eyeOS. This hybrid encryption algorithm the servers are potentially based at multiple locations and optimizes the results for both computation time and security. the services provided by the cloud may use different infrastructures across organizations, all these Keywords; cloud computing, Encryption, key encryption, characteristics make Cloud Computing to be complicated eyeOS ,eyeOS advanced, advanced standard encryption , to guarantee security [7,8]. Rivest-Shamir-Adleman. On the other hands, Cloud Computing security refers to a 1. Introduction broad set of policies, technologies, and controlsdeployed Cloud Computing is a set of IT Services that are provided to protect data, applications, and the associated to a customer over a network and these services are infrastructure of cloud computing. It should be noted that delivered by third party provider who owns the Cloud Computing security is not cloud-based security infrastructure. It is often provided "as a service" over the softwareproducts such as cloud-based anti-virus, anti- Internet, typically in the form of infrastructure as a spam, anti-DDoS,and so on [12]. service (IaaS), platform as a service (PaaS) and software as a service (SaaS) [23]. Cloud computing security includes a number of issues like multi tenancy, data loss and leakage, easy Cloud computing is a technology that keeps up data and accessibility of cloud, identity management, unsafe API’s, its applications by using theInternet and central remote Service Level Agreement, inconsistencies, patch servers [1]. It introduces a new supplement, consumption, management, internal threats etc. It is not easy to enforce and delivery model for IT services based on Internet all the security measures that meet the security needs for protocols, and involves provisioning of dynamically all the users, because different users may have different scalable and often virtualized resources. This may take security demands based upon their objective of using the the form of web-based tools or applications that the users Cloud services [13]. can access and use through a web browser [2]. Also, Cloud Computing provides much more efficient There are many security issues associated with Cloud computing by centralizing storage, memory, processing Computing and they can be grouped into any number of and bandwidth. Resources are accessible from the Cloud dimensions (see Figure 1) [12]. at any time and from any place across the globe using the Internet, and the Cloud users only pay for the resources The cloud users can remotely store their data and enjoy allocated to them [3,4,5].Among the development of the on-demand high-quality applications and services distributed computing, parallel computing and grid from cloud resources. The data security is one of the computing, Cloud Computing is considered the business major concerns as the users of cloud storage services no realization of all these concepts [6]. longer physically maintain direct control over their data in cloud. Thus shifting of all data over the cloud has Three services could be provided by Cloud Computing; implications for privacy and security.[24] SaaS (Software as a service), PaaS (Platform as a service), Volume 3, Issue 3 May – June 2014 Page 278 International Journal of Emerging Trends & Technology in Computer Science (IJETTCS) Web Site: www.ijettcs.org Email: editor@ijettcs.org, editorijettcs@gmail.com Volume 3, Issue 3, May-June 2014 ISSN 2278-6856 There are different types of cloud operating systems Asymmetric Key Cryptography – uses two different keys including Glide , Amoeba , My Goya , Kohive, Zimdesk called public key and private key; one is used for , Ghost , Joli, Cloudo, Corneli , Lucid , EyeOS , encryption andanother for decryption. Startforce, etc .The most used one as Web Operating system is EyeOS [11]. Common asymmetric encryption algorithms include The Rivest-Shamir-Adleman (RSA),ElGamal and Rabin. RSA According to the work in this paper, the EyeOS is algorithm is the first asymmetric algorithm that was installed on ubuntu server which is installed on VMware discovered in 1978, and it is still one of the mostefficient (cloud services). Two security algorithms are applied; the and used algorithm this day. The RSA cipher represented advanced encryption standard (AES) which is a a real turning point for practical applications with high symmetric algorithm, and the Rivest-Shamir- quality, guaranteed security and reliability. In fact, the Adleman(RSA)which is asymmetric[3]. expression "strong encryption" was invented exactly with the RSA algorithm [4]. This paper is organized as follows; encryption algorithms are discussed in section 2, the Proposed Hybrid Security 2.1 The Advanced Encryption Standard(AES) Algorithm Algorithm is presented in section 3. Also, the Simulator The AES algorithm was known as Rijndael. Rijndael has Environment, the Evaluating parameters and The named after two Belgian cryptographers, Dr. Joan Implementation Results are presented in section 4; Daemen and Dr. Vincent Rijmen, have developed and conclusion is presented in section 5. submitted it [15]. AES, Like DES, AES, is a symmetric block cipher. This means that it uses the same Key for both encryption and decryption. Rijndael Algorithm allows for a variety of block and key size to be used rather than 64 and 56 bits of DES’ block and key size. The block and key can be chosen independently from 128, 160, 192, 224, 256 bits and need not be the same. However, the AES standard states that the algorithm can only accept a block size of 128 bits and a choice of three keys , 128, 192, and 256 bits. Also, the AES algorithm differs from the DES algorithm where it is not a Feistel structure, but it is based on substitution- permutation network. In most ciphers, the iterated transform (or round) usually has a Feistel Structure. Typically in this structure, some Figure 1: Cloud Computing Security [12] of the bits of the intermediate state are transposed unchanged to another position (permutation). AES does not have a Feistel structure but is composed of three 2. Encryption Algorithms distinct invertible transforms based on the Wide Trial In Cloud Computing technology, there are a set of Strategy design method. important policy issues like privacy, security, anonymity, telecommunications capacity, and reliability. The most Wide Trail Strategy important issue is security and how the Cloud provider The Wide Trial Strategy design method provides assures it [14]. resistance against linear and differential cryptanalysis such that, every layer has its own function [21]: On the other hands, encryption algorithm is a The linear mixing layer: guarantees high diffusion over mathematical procedure that is used to encrypt the data. multiply rounds According to the encryption algorithm, the data is The non-linear layer: parallel application of S-boxes that encoded into cipher text and requires the use of a key to have the optimum worst-case non-linearity properties. transform the data back into its original form. The key addition layer: a simple XOR of the round key to the intermediate state There are two types of cryptographic schemes are On the other words, in a Feistel structure, half of the data available [15]: block is used to modify the other half of the data block Symmetric Key Cryptography – uses a common key for and then the halves are swapped. In this case the entire both encryption and decryption of themessage. Common data block is processed in parallel during each round symmetric encryption algorithms include Data Encryption using substitutions and permutations. Standard (DES), Triple Data Encryption Standard (3DES), Advanced Encryption Standard (AES), and RC4. The AES algorithm provides flexibility, simplicity for In this paper, the AES is concerned rather than others hardware and software sustainability. This algorithm can because of its excellent security [15]. be used in a variety of platforms andapplications. Volume 3, Issue 3 May – June 2014 Page 279 International Journal of Emerging Trends & Technology in Computer Science (IJETTCS) Web Site: www.ijettcs.org Email: editor@ijettcs.org, editorijettcs@gmail.com Volume 3, Issue 3, May-June 2014 ISSN 2278-6856 The number of AES parameters is depending on the key hexadecimal value {95} references row 9, column 5 of the length. For example, if the used key sizeis 128, then the S-box, which contains the value {2A}. Accordingly, the number of rounds is 10. The number of round for 192 and value {95} is mapped into the value {2A} (See Figure 256 bits are 12 and 14 respectively. 3)[20]. The AES is a block cipher with a block length of 128 bits. The S-box, then, is a function on a byte in State s so that: According to the work in this paper, the AES algorithm s'i,j = S-box (si,j) with 128 bit key length is concerned. The encryption process consists of 10 rounds of processing for 128-bit keys. Except for the last round in each case, all other rounds are identical. For encryption, each round consists of the following four phases [16]: SubBytes – a non-linear substitution step where each byte is replaced with another according to a lookup table or substitution table(S-box). ShiftRows – a transposition step where each row of the state is shifted cyclically a certain number of times MixColumns – a mixing operation which operates on the columns of the state, combining the four bytes in each Figure 3 : SubBytes Transformation Step [20] column. AddRoundKey – XORs a key that is the same length as 2.1.2 ShiftRows Phase the block, using an Expanded Key derived from the The purpose of this phase is to provide diffusion of the original Cipher Key bits over multiple rounds. ShiftRows essentially consists For the final round only three steps are performed of shifting the bytes in the row. It is a transposition step ;SubBytes, ShiftRows and AddRoundKey (See Figure 2). on the row of the state where each row of the state is shifted cyclically by certain number of steps. The first row (row 0) is not shifted. The second row (row 1) is shifted by one byte, the third row is shifted by two bytes and final row is shifted by three bytes. It also ensures that each byte in each row does not interact solely with their corresponding bytes. The transformation is shown in Figure 4. Figure 2: Four steps in each round in AES encryption and decryption Figure 4: ShiftRows Transformation Step 2.1.1 SubBytesPhase The Substitution table (S-box) matrix consists of all the 2.1.3 MixColumns Phase possible combinations of an 8 bit sequence (28= 16 × 16 Like ShiftRows phase, the purpose of this step is to = 256). However, the S-box is not just a random provide diffusion of the bits over multiple rounds. This is permutation of these values and there is a well-defined achieved by performing multiplication one column at a method for creating the S-box tables. time. During this operation, each column is multiplied by the known matrix Galois field GF and is shown in Figure 5. SubByte transformation is a nonlinear substitution that Each value in the column is multiplied against every row operates on individual bytes using a S-box, controls the value of a standard matrix. The results of this transformation.. Each individual byte of state (input multiplication are XORed together. The multiplication matrix) is mapped into a new byte as the following way: operation continues against one matrix row at a time for These row and column value serve as indexes into the S- each value of a state column. box to select a unique 8-bit output value. For example, the Volume 3, Issue 3 May – June 2014 Page 280 International Journal of Emerging Trends & Technology in Computer Science (IJETTCS) Web Site: www.ijettcs.org Email: editor@ijettcs.org, editorijettcs@gmail.com Volume 3, Issue 3, May-June 2014 ISSN 2278-6856 The multiplication operation is defined as; Multiplication 2.2 The Rivest-Shamir-Adleman (RSA) Algorithm by 1 means leaving unchanged, multiplication by 2 means The RSA is an algorithm for public-key cryptography. It shifting byte to the left by 1 position and multiplication by is the first suitable algorithm to be used for encryption. 3 means shifting to the left by 1 position and then TheRSAalgorithm is widely used in the electronic performing XOR with the initial unshifted value. commerce protocols, and is consideredto be secure by given sufficiently long keys and the use of up-to-date implementations [4]. The RSA algorithm includes three phases. Key generation Encryption, and Decryption 2.2.1 Key GenerationPhase The RSA algorithm includesa public key and a private Figure.5: MixColumns Phase key. The public key can be known to everyone and it is Transformation Step used for encrypting messages. The encrypted Messages by the public key can only be decrypted using the private 2.1.4 AddRoundKey Phase key. The keys for the RSA algorithm are generated by the In this phase, the 128 bits of State matrix is XORed with following steps: the 128 bits round key. The original key consists of 128 Select two prime numbers. bits/16 bytes which are represented as a 4x4 matrix. This Calculate n = p*q. 4 words key where each word is of 4 bytes is converted to Calculate f(n) = (p-1)(q-1) a 43 words key. The first four words represent W0, W1, Select e such that e is relatively prime to f(n) and less W2, and W3. The rest of expanded key, W[4] to W[43] is than f(n). generated as follows:- Determine d such that congruent modulo 1 (mod f(n)) for (i = 4; i<44; i++) and d<f(n). { Public key = {e, n}, Private Key = {d, n}. T = W[i-1]; if (i mod 4 = = 0) 2.2.2 EncryptionPhase T = Substitute (Rotate (T)) XOR RConstant [i/4]; Ciphertext c = message e mod n W[i] = W[i-4] XOR T; } 2.2.3 Decryption Phase Expanded Key: W0 W1 W2 W3 W4 W5 W6 W7 Plaintext p = Ciphertextd mod n ... W48 W49 W50 W51 Round keys: Round key 0 Round key 1 ... Round key Symmetric Encryption Advantages: 12 Provides authentication, as long as the key to be secret. The encryption process is fast. Where, Rotate means perform a one byte left circular Symmetric-key ciphers can be designed to have high rates rotation on the 4-byte word, Substitute means perform a of datathroughput. byte substitution for each byte of the word, using S-box, Keys for symmetric-key ciphers are relatively short. also used in the SubBytes step, and RConstant means Symmetric-key ciphers can be employed as primitives to Round Constant (size of 4 bytes) which is XORed with construct various cryptographic mechanisms including the bytes. The rightmost three bytes of the round constant pseudorandom number generators, hash functions, and are zero. In this way, W [4] to W [43] of the key schedule computationally efficient digital signature schemes, to isgenerated from the initial four words. name just a few. Although, overall, the same steps are used in decryption, Symmetric-key ciphers can be composed to produce as in encryption, the order in which the steps are carried stronger ciphers. Simple transformations which are easy out is different (See Figure 6). to analyze, but on their own weak, can be used to construct strong product ciphers. Symmetric Encryption Disadvantages: In a two-party communication, the key must remain secret at both ends. In a large network, there are many key pairs to be managed. Consequently, effective key management requires the use of an unconditionally trusted TTP. In a two-party communication between entities A and B, Figure 6: AES key expansion sound cryptographic practice dictates that the key has be Volume 3, Issue 3 May – June 2014 Page 281 International Journal of Emerging Trends & Technology in Computer Science (IJETTCS) Web Site: www.ijettcs.org Email: editor@ijettcs.org, editorijettcs@gmail.com Volume 3, Issue 3, May-June 2014 ISSN 2278-6856 changed frequently and perhaps for each communication asymmetric algorithm, and the key distribution session. complexity of the symmetric algorithm). Digital signature mechanisms arising from symmetric- The phases of the proposed hybrid security algorithm are key encryption especially if keys change implemented as follows: frequentlytypically require either large keys for the public 3.1 Session key Phase verification function or the use of a TTP,because they Session key is not an asymmetric key, but it is only used allow accessing all the encrypted Information during the session life cycle. In fact, a symmetric key is Advantages of Using Asymmetric Encryption produced by two entities every time they create a new Only the private key must be kept secret (authenticity of session. After the session life cycle, the key is destroyed. public keys must, This provides more robust level of security, where if a however, be guaranteed). hacker captures a session key, he would only be able to For any number of users (represented as “n”), only 2*n, use this key during that session but not any future (N=2*n) keys are required instead of n*(n-1)/2 by using sessions, because it is destroyed after the session life symmetric encryption. For example if the number of users cycle. n=3, then they use N=6keys,.Using asymmetric encryption, each user has only 1 key pair. This means that 3.2 Encryption Phase only a user’s public key is exchanged and each group of According to the hybrid algorithm, the sender's plaintext people does not need separate keys. document is compressed to reduce its size and Depending on the mode of usage, a private key/public key strengthening its cryptographic security. The proposed pair may remain unchanged for considerable periods of hybrid algorithm would create a symmetric key (e.g., time, e.g., many sessions even several years). random number session key).Then, the session key is The problem of distributing keys is solved because a user processed using asymmetric encryption algorithm such as ’s public key can be AES which generates a one-time-only secret key Shared by anyone [Rijndael]. Many public-key schemes yield relatively efficient digital signaturemechanisms. The key used to describe the public verification function is typically much smaller than for the symmetric-key counterpart. In a large network, the number of keys necessary may be considerablysmaller than in the symmetric-key scenario. . Disadvantages of Using Asymmetric Encryption: Asymmetric encryption algorithm is slower than that symmetric one Some algorithms are only suitable for key distribution Throughput rates for the most popular public-key encryption methods are several orders of magnitude slower than the best-known symmetric-key . Key sizes are typically much larger than those required Figure 8: The Encryption Phase for symmetric-keyencryption, and the size of public-key signatures is larger than that of tags The session key is used by symmetric encryption Providing data origin authentication from symmetric-key algorithm to encrypt the plaintext; the result is ciphertext. techniques. Once the data is encrypted, the session key is then encrypted to the recipient’s public key, using asymmetric Summary of comparison encryption such as RSA 1. Public-key cryptography facilitates efficient signatures (particularly non repudiation) and key management, and This public key-encrypted session key is transmitted 2. Symmetric-key cryptography is efficient for encryption along with the ciphertext to the Recipient. The main and some data Integrity applications. components of the proposed hybrid algorithm are seen in 3. The Proposed Hybrid Security Algorithm Figure8 The asymmetric algorithms are much slower than that the 3.3 Decryption Phase symmetric algorithms, especially with large amounts of Decryption process is done in the reverse way of the data. On the other hands, using the symmetric algorithm encryption process. The recipient’s copy of the proposed as key distribution is considered a problem because it hybrid algorithm uses his or her private key to recover the can't prove the authenticity and non-repudiation. session key, and then the hybrid algorithm uses the Therefore, by amalgamating both the symmetric and session key to decrypt the symmetrically encrypted asymmetric encryption algorithms, the drawbacks of these ciphertext (See Figure 9). algorithms would be eliminated (i.e., the speed of the Volume 3, Issue 3 May – June 2014 Page 282 International Journal of Emerging Trends & Technology in Computer Science (IJETTCS) Web Site: www.ijettcs.org Email: editor@ijettcs.org, editorijettcs@gmail.com Volume 3, Issue 3, May-June 2014 ISSN 2278-6856 input sizeas24 byte, 36 byte, and 61 byte. The encrypted time of these algorithms are listed in Table 1. Table 1: Encryption Times of RSA, AES, and Proposed Hybrid Algorithms Input Data Size RSA AES Hybrid Improved % Figure 9: Decryption phase With respect to RSA Improved %With respect to AES 4 The Implementation 24 bytes The hybrid algorithm has been implemented on cloud 8 ms 6 ms 0.062 ms 99.2 98.96 platform (eyeOS) which is installed on ubuntu linux that 36 bytes is installed on VMware(cloud service). 6 ms 2 ms 0.049 ms 99 97.55 4.1 The Simulator Environment 61 bytes The eyeOS simulator is used to implement the proposed 30 ms 12 ms 0.05 hybrid algorithm. On the other hands, eyeOS is ms 99.8 99.58 considered cloud computing platform and enabled thecollaboration and communication among users. It is According to the results in Table 1, it is found that the mainly written in PHP, XML, and JavaScript. Generally, encryption phase using the hybrid algorithm outperforms it considered a private-cloud application platform with a the AES, RSA algorithms (See Figures 10). web-based desktop interface[11]. On the other hands, eyeOS is one of the most used By analyzing Figure 10, it is found that the proposed WebOSes which only needs Apache + PHP5 + MySQL to hybrid security algorithm improves the speed of the run. With eyeOS you can build your private Cloud computation time. Desktop. Using eyeOS Web Runner you can open your eyeOS files from your browser with your local apps and save them automatically on your cloud. In eyeOS 2.0 you can work collaboratively with other users simultaneously in the same document, it is the Safe Cloud Computing system because you can host it in your own company or organization. You will get privacy and cloud computing at its best.[22] 4.2 The Evaluating Parameter: The performance of the encryption algorithm is evaluated by calculating the encryption time parameter. The Encryption time is the time that an encryption algorithm Figure 10: Encryption time of The AES, RSA and Hybrid takes to produce a cipher text from a plain text in the case Algorithms of encryption. Also, the time will be taken to produce plain text from cipher text in case of decryption is used as a parameter to evaluate the proposed hybrid security 5. Conclusions algorithm performance. The goal of encrypted storage in the cloud is to create a virtual private storage system that maintains confidentiality and data integrity which are provided by AES algorithm, but RSA algorithm provides 4.3 The Implementation Results: The encryption phase of the proposed hybrid algorithm, authentication, encryption and key distribution. as well as, the RSA and AES algorithms, have been The public-key encryption RSA algorithm provides a implemented on eyeOS simulator using different data solution to the key distribution and data transmission issues of the AES symmetric encryption algorithm. On Volume 3, Issue 3 May – June 2014 Page 283 International Journal of Emerging Trends & Technology in Computer Science (IJETTCS) Web Site: www.ijettcs.org Email: editor@ijettcs.org, editorijettcs@gmail.com Volume 3, Issue 3, May-June 2014 ISSN 2278-6856 the other hands, by using the symmetric encryption [13] SachdevAbhaThakral, and MohitBhansali. algorithm (i.e., AES algorithm) is satisfied about 100 to "Addressing the Cloud Computing Security 1,000 times faster than that the public-key encryption Menace." IJRET, Volume 2, Issue 2, PP. 126-130, RSA algorithm, which solves the problem of speed of the Feb 2013. encryption asymmetric algorithms. [14] Mandeep Kaur, Manish Mahajan,"Implementing various encryption algorithms to enhance the data According to the hybrid algorithm, using the faster security of cloud in cloud computing" VSRD algorithm (i.e., Symmetric algorithm) to encrypt the bulk International Journal of Computer Science & data and the slower but scalable algorithm (i.e., Information Technology, Vol. 2 No. 10 October 2012 Asymmetric algorithm) is used to encrypt the small [15] William Stallings, “Cryptography and Network amount of data (the key). According to the proposed Security Principles and Practices”, 4th ed., Prentice hybrid algorithm, a secure system has been satisfied Hall, PP. 134-173. November 2005. which would provide scalability, speed and more security [16] Bruce Schneier, “Applied Cryptography, Protocols, (confidentiality, data integrity,and authentication). Algorithms and Source Code in C”, 2nd ed., John Wiley& Sons, 1996. 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