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Multimedia Encryption with Multiple Modes Product Cipher for Mobile Devices 184 JOURNAL OF ELECTRONIC SCIENCE AND TECHNOLOGY, VOL. 16, NO. 2, JUNE 2018 Multimedia Encryption with Multiple Modes Product Cipher for Mobile Devices Yi-Nan Lin, Gwo-Jen Chiou, and Victor R. L. Shen Abstract—The most straight forward method in because it encrypts each block independently. Its multimedia encryption is to encrypt the entire stream disadvantage is that identical plaintext blocks are encrypted using standard encryption methods, such as the data into the identical ciphertext blocks. encryption standard (DES) or advanced encryption Unfortunately, non-feedback conventional block ciphers do standard (AES). However, in the block ciphering, there not hide data patterns well. Non-feedback conventional block exists an attack risk with the weakness of plaintext- ciphers have plaintext-ciphertext pair problems with the ciphertext pairs (i.e. the plaintext-ciphertext pair disadvantages of limiting block region scrambles. A crack can problem). Therefore, several modes of operation are use it to perform a known-plaintext attack. In some senses, it proposed to solve the above problem. As we all know, cannot provide serious message confidentiality. A non- channel hopping can defend illegal listening. Thus, this feedback conventional block cipher is not recommended at all paper has proposed a multimedia encryption scheme for use in cryptographic protocols. with the multiple modes product cipher (MMPC) for As the images are shown in Fig. 1, the original image in a mobile devices. In practice, MMPC can increase the pixel-map version in Fig. 1 (a) is encrypted with a electronic security level in wireless multimedia networks. The codebook (ECB) mode to create the encrypted image in results of Android applications (Apps) system have Fig. 1 (b). Following the original image or the encrypted shown that the overhead of MMPC is decreased by 2% image is the number of colors used in the image and the in throughputs, if it is compared with that of the other image’s histogram. Fig. 1 (b) represents the ECB DES straightforward mode ciphers. encryption of the original image using the key 1234567890ABCDEF. Index Terms—Advanced encryption standard (AES) encryption, blockwise, confidentiality, dynamical operation model, multi-mode cipher. 1. Introduction # Colors used=9 # Colors used=256 In the wireless networks, the confidentiality of private information is protected[1]-[3]. A block cipher itself only allows the encryption to be performed with a single data set in the cipher’s block length. Block encryption may be vulnerable to ciphertext searching, replaying, insertion, and deletion Manuscript received May 24, 2017; revised September 25, 2017. Fig. 1. One sample image with an image resulted from its This work was supported by MOST under Grant No. MOST 103- encryption: (a) original image and (b) ECB data encryption 2221-E-305-015. standard (DES) encryption of the original image. Y.-N. Lin is with the Department of Electronic Engineering, Ming Chi University of Technology, New Taipei 243 (e-mail: jnlin@mail. mcut.edu.tw). The non-feedback ECB mode can leave plaintext data G.-J. Chiou is with the Department of Electrical Engineering, patterns in the ciphertext. In Fig. 1, a striking example of the National Formosa University, Huwei Township 632 (e-mail: [email protected]). degree can be seen when the electronic codebook mode is used V. R. L. Shen (corresponding author) is with the Department of to encrypt a bitmap image which contains large areas of Computer Science and Information Engineering, National Taipei uniform color. The overall image may still be discerned as the University, New Taipei 237, and also with the Department of Information Management, Chaoyang University of Technology, pattern of identically-colored pixels in the original image Taichung 41349 (e-mail: [email protected]; victor.rlshen@ remained in the encrypted version while the color of each msa.hinet.net). individual pixel is encrypted. Block cipher modes of encryption Color versions of one or more of the figures in this paper are available online at http://www.journal.uestc.edu.cn. different from the non-feedback ECB mode have been Digital Object Identifier: 10.11989/JEST.1674-862X.70524018 suggested to remedy these drawbacks. The straightforward LIN et al.: Multimedia Encryption with Multiple Modes Product Cipher for Mobile Devices 185 block ciphering mode of operation (also called ECB mode) is requirements of confidentiality, multimedia security often uses not considered to be secure, because it is vulnerable to encryption software to ensure the safety of computational statistical attacks[4]. complexity in the multimedia. Notice that the common thing The standard modes of operation are described in the between compression and encryption is that both try to remove literatures[5] such as non-feedback electronic codebook (ECB) redundant information[17]. mode, cipher block chaining (CBC) mode, output feedback There are several encryption algorithms, such as the naive (OFB) mode, and cipher feedback (CFB) mode. They can all algorithm and selective algorithm to secure multimedia provide confidentiality. But how to choose an appropriate contents. The naive method is to encrypt the entire multimedia operation mode becomes an important issue. Different modes contents using standard encryption methods such as DES and have different characters. For example, both CFB and OFB can AES. Each of them has its strength and weakness in terms of be designed to operate without padding with bit-based size the security level, speed, and resulting stream size metrics. For keystream output. BothCBCand CFB can self-synchronize to example, in the Moving Picture Experts Group (MPEG) avoid the channel noise error propagation.For CFB and OFB, contents, the basic selective algorithm is based on the MPEG their encryption and decryption need only one encryption IPB frames structure. Encrypting only I-frames does not module to reach both usages. In addition, only the forward provide a satisfactory secure level, because great portions of the cipher function of the block cipher algorithm is used in both video are visible, partly dependent on the inter-frame encryption and decryption, without the need for the inverse correlation and mainly dependent on the unencrypted I-blocks cipher function[1]. in P-frames and B-frames[18]. The rest of this paper is organized as follows. Section 2 Zigzag-permutation algorithm[19], where the encryption is an contains the review of ciphers and video encryption algorithm integral part of the MPEG compression process, uses a random (VEA). Section 3 describes how to make multiple modes permutation list to map the individual 8×8 block to a 1×64 ciphering with a secured mode sequence and the multiple vector in “zigzag”. It consists of three steps: Step 1, modes product cipher (MMPC). Section 4 is the security generate a permutation list with cardinality of 64. Step 2, do analysis. Section 5 contains the practical implementation of the splitting procedure. Step 3, apply the random permutation mobile devices and performance evaluation. Finally, the list to the split block. conclusion is remarked in Section 6. In 1998, [17] described, evaluated, and compared five representative MPEG encryption algorithms with respect to the 2. Literature Review encryption speed, security level, and stream size. It indicates that there are trade-offs among performance evaluation metrics. Currently, data confidentiality is one of the security The choice of encryption algorithm will depend on the security services in cryptography. The major concept in information requirements of the multimedia applications. Study on MPEG security is to continue to improve encryption algorithms. There properties and its statistical behavior lead to the video are two major types of encryption algorithms in cryptography, encryption algorithm (VEA). In Fig. 2, VEA is mainly [6],[7] namely, symmetric-key algorithms and public-key interested in dealing with the MPEG stream in a byte-by-byte [8],[9] algorithms . Symmetric-key algorithms also referred to as fashion due to the following reasons: 1) It is easier to handle conventional encryption algorithms or single-key encryption data byte-wise; 2) a single byte is meaningless in multimedia algorithms are a class of algorithms that use the same stream because, normally, the multimedia content is encoded in cryptographic keys for both encryption of plaintext and several bytes. This is different from text information where one decryption of ciphertext. So far, it has remained the above two byte or character has its own meaning. Therefore, VEA is used types of encryption algorithms most widely used. to convert an MPEG bit stream into a byte stream. And each Symmetric-key ciphers are a class of ciphers in unit has an integer between 0 and 255. cryptography. They use trivially related cryptographic secret keys for both encryption of plaintext and decryption of ciphertext. Symmetric-key cryptography is here to be 3. MMPC contrasted with asymmetric-key cryptography. Symmetric-key cryptography is the only one type of encryption in use prior to The idea of using multiple confidentiality modes with a the development of asymmetric-key cryptography[10],[11]. The secured mode sequence to increase the security level of advanced encryption standard (AES)[12]-[14] algorithm approved multimedia is described in this Section, . The traditional block by National Institute of Standards and Technology (NIST) in ciphers have a plaintext-ciphertext pair problem with the December 2001 uses 128-bit blocks. disadvantages of limiting block region scrambles. In the Multimedia data sets have special characteristics, such as literature[5],[20], standard operational modes for data coding structure, large amount of data, and real-time confidentiality are specified using any approved block cipher, constraints. A multimedia stream is quite different from the such as the AES algorithm[12]-[14]. The operational modes are traditional textual data because it has a special data structure ECB, cipher block chaining (CBC), cipher feedback (CFB), and is also compressed[15],[16]. To provide the security output feedback (OFB), and counter (CTR).
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