A Secure Communication Platform Based on Gemstone Yanjiao Chen, Jian Wang, and Ruming Yin Bo Liang
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201O 3rd InternationalConference on AdvancedComputer Theoryand Engineering(ICACTE) A Secure Communication Platform Based on Gemstone Yanjiao Chen, Jian Wang, and Ruming Yin Bo Liang Dept. of Electronic Engineering, Tsinghua University AQSIQ Information Center Beijing 100084, China Beijing 100088, China [email protected] [email protected] Abstract-In this paper, we have implemented a secure FUBUKI based on a non-secure pseudo-random number communication platform based on a new stream cipher called generator (the mother generator) [9]. Gemstone which stems from coupled map lattices (CML), a Gemstone is also a candidate of eSTREAM, motivated nonlinear system of coupled chaotic maps. On the platform, we have realized duplex text, image and voice transmission. We by coupled map lattice (CML), a real-valued nonlinear have also analyzed the randomness of the keystream generated system of coupled chaotic maps [10]. While preserving good by the platform based on the statistical tests suggested by the confusion and diffusion property of CML, Gemstone National Institute of Standards and Technology (NIST). The properly discretizes the CML, improving the security as well test results are compared with other four stream ciphers'. as the performance. In addition, Gemstone is robust against Moreover, a series of experiments of duplex text, image and voice transmissions were made through university local IV setup attacks since there are no high probability network. Both the statistical test and the transmission difference propagations or high correlations over the IV experiments have shown that the platform is highly secure with setup scheme [10]. fast encryption speed, which confirms that the Gemstone In this paper, we have built a secure communication platform is promising for cryptographic applications. platform on which Gemstone is used for data encryption. We Keywords-CML (coupled map lattices); stream cipher; also set the statistical tests on the platform including Gemstone; encryption; decryption; statistical test. Frequency test, Runs test and Spectral test (also known as DFT test) to evaluate the randomness of the keystream. I. INTRODUCTION The results are compared with other four stream ciphers: th 20 century saw a rapid expansion of wireless Rabbit, FUBUKI, Yamb and a primitive algorithm based on communication. As wireless platforms grow in popularity CML (We refer to this algorithm as Chaotic algorithm in this and store valuable information, security is becoming an paper), which verify that the keystream generated by the important area of research and development. Encryption is a platform has ideal random properties. The experiments of conventional way to protect the wireless link. Compared duplex text, image and voice transmissions via university with block ciphers, stream ciphers can be faster and have local network have further proved that the platform can limited error propagation [1]. Therefore, stream ciphers are ensure security and fast encryption speed. widely adopted in wireless communication. For instance, The rest of the paper is organized as follows. Section 2 GSM uses the A5/I and A5/2 stream ciphers for ensuring gives brief introduction to Gemstone. The implementation of over-the-air voice privacy [2]; The EO stream cipher is used the secure communication platform is described in Section 3. for encrypting packets in Bluetooth [3]; In IEEE 802.11 In Section 4, we present the statistical test results. Also, a standard, Wireless Equivalent Privacy (WEP) uses the particular description of duplex image transmission on the stream cipher RC4 for confidentiality [4]; so does Wi-Fi platform is given. Conclusions and discussions are in Section Protected Access (WPA), a further enhancement of WEP. In 5. 2000, New European Schemes for Signatures, Integrity and Encryption (NESSIE) was funded to identify secure II. A BRIEF INTRODUCTION OF GEMSTONE cryptographic primitives. Stimulated by NESSIE, eSTREAM Gemstone is a synchronous stream cipher, using a I28-bit project arises to further promote the study of "new stream key K and a 64-bit initialization vector IV. A long ciphers that might become suitable for widespread adoption" pseudorandom key stream is generated based on the state [5]. variables and counter variables, after which the bitwise XOR There is a great number of stream cipher algorithms of the key stream and the plaintext is computed to produce proffered both in academia and in industry. Rabbit is one of ciphertext [10]. the candidates of the eSTREAM, proposed by Martin The 256-bit internal state of the cipher is divided into Boesgaard [6]. In [6] [7], a comprehensive security analysis eight I6-bit state variables Xi,n and eight I6-bit counter has been made, confirming Rabbit's resistance to some variables Ci,n • Xi,n is the i-th I6-bit state variable at iteration n conventional attacks. Yamb, another candidate, is described and Ci,n is the corresponding I6-bit counter variable. in details in [8]. MAKOTO MATSUMOTO has proposed 1) The state-update fu nction: 978-1-4244-6542-2/$26.00 © 2010 IEEE V2-527 2010 3rd International Conference on AdvancedComputer Theoryand Engineering(1CACTE) The state-update function is shown in Figure 1, in which S denotes iteration of discretized CML for times, i.e., (7) N 5 = EB Sl,n = x ,n EElx l,n ' so,n x4,n xo,n S(T) = VN (T +1)- 1, (1 ) In our previous work, we proved that there are no high where V represents discretized CML as (2). As for the parameters of S-box, A is usually set as 16409 probability difference propagations or high correlations over and N is 20. Addition modulo M=216 is chosen to modify the IV setup scheme. So Gemstone is resistant against the nearest neighbour coupling in CML. differential and linear cryptanalysis attacks [11 ]. We also Z showed the linear correlations between consecutive key {1 � l IS;;ZS;;A stream bits of Gemstone are below the safe bounds [10]. v(z)= (2) Thus, Gemstone should be very secure. l M<:-�Z)J + l, III. PLATFORM IMPLEMENTATION r--------� 1--------, The schematic figure of the secure communication I I g I I g C/." I I I platform is given in Figure 2. I I I I I I ... .. .. .. ... Xi,,,+1 : I 1--T1--II-+lD2 S21--'- 1 �-++- I r"'"'''''''''''''''''''' �;:,;,"� �--------... I y,... Ig"'l "i.. I /". L ________ -' L ________ I : :.i __________ J i Kcyslrcarn Figure 1. State-Update function. D denotes mixing transformation: lnSCClln: 11 00 ··· 1 channel 1110 ··· 0 D= 0111 ··· 0 (3) K�yslrcam Gemstone 1000 ··· 1 The counter variables are updated during each iteration Figure 2. Schematic figureof the secure communication platform based on according to a maximum-length LFSR as: Gemstone. lO] C(I5.. .! ] cI ,n+l =c l+l,n <l i,n ' 0 S;;i S;; 6 (4) IIS.. .! The platform consists of four modules: Encoding Module, = m <l ] , i =7 cl ,n+l 'r ct,n Encryption Module, Decryption Module and Decoding where <l denotes concatenation of two bit sequences and Module. The Encoding Module includes text/image entry 4 m= C11 5] EB C(I ] EB 19] EB lO] "f" 7,n 7,n c7,n cD,n • and sound recording. After input, the text, image or sound is transformed into byte streams which will be processed into 2) Key setup and IV setup: The counter variables are initiated with carefully selected the Encryption Module. Then, the plaintext is encrypted by values and the state variable with the key. Then, the Encryption Module into ciphertext, which will then be state-update function is iterated three times to spread the transmitted through insecure channel. In the Decoding influence of each key bit over all the state variable bits. Module, the byte streams are re-transformed into text/image Finally, the counter variables are modified as: or sound. The Encryption/Decryption Module is the core of C the platform, including parameter setting, IV key setup i,3=Ci,3EElXi,3' i=0,1, ···,7 (5) & and key generation. The 64-bit IV is divided into four 16-bit variables IVO, The interface of the platform is depicted in Figure 3 and lVI, IV2, IV3 and the state variables will be modified using Figure 4. The platform can conduct secure transmissions of the IV as follows: text, image and voice. i =0,1, 2,3 Figure 3 exhibits the typical interface of duplex secure (6) EB Xi,3= rv,_4 Xi,3' i =4, 5,6,7 text transmission. Once the "Connection Establishment" button is pressed, a dialog box pops out in which users can Then, the state-update function is iterated two times to input the "Local Address" and "Local Port" as well as spread the influence of each IV bit over all the state variable "Server Address" and "Server Port". Then, a link is bits. established which enables transmitter to send encrypted 3) Key stream generation: message to receiver in security. Both the plaintext and After each iteration, 64 bits of key stream are generated ciphertext are displayed on the two Textboxes. as (7). The encryption is processed by bitwise XOR of the key stream sn and the plaintext to form the ciphertext. V2-528 2010 3rd International Conference on AdvancedComputer Theoryand Engineering(1CACTE) secure text, image and voice transmission through university local network based on the platform. As the space is limited, we only elaborate on the result of secure image transmission here. The statistical tests and experiments are performed with Intel Pentium 4 3.00GHz processor and 2.00GB RAM. A. Statistical test Randomness is a probabilistic property. There are 3 steps to conduct a statistical test: 1) SpecifY the null hypothesis. In this paper, the null hypothesis (HO) is "the sequence under test is random"; 2) Compute randomness statistic; 3) Compute the P-value. If P-value � a, we demonstrate that the sequence is random.