 Proceedings of Engineering and Technology Innovation , vol. 3, 2016, pp. 04 - 06 4 Security Enhancement on Reconfiguring Coded Wavelength with Tunable Wavelength Filter Array Triggered Chaotic Sequences Yao-Tang Chang 1,* , Jen-Fa Huang 2 , Yen-Chung Huang 2 and Yan-Tai Liou 1 1 Department of Information Technology, Kao Yuan University, Kaohsiung, Taiwan . 2 Department of Electrical Engineering, National Cheng Kung University, Tainan, Taiwan . Received 02 February 2016; received in revised form 17 March 2016; accept ed 02 April 2016 Abstract In current study, the reconfigurab le opt ical code-div ision mu lt iple -access (OCDMA ) scheme is imp le mented that the chaos sequence is c reated non-linea r time-va riant sequence as secret key and then t rigger tunable wavelength filte r array as rando m wavelength allocation . In the encryption, the distribution o f light ca rrie r is designed and imp le mented by using tunable wave length filte r array triggered chaot ic se- quence. In add ition, the a rrayed wavegu ide grating (AW G) router is re written with ma xi- mal length code (M-sequence) to act as encoder. In the decryption, sy mmet ric sche me and ba l- anced photo-detector is presented and recon- figu rable mechanis m is fo llowed the enc ryption synchronously either public o r p rivate channel. Hence, the mu ltip le ac cess interfe rence (MAI) is cancelled co mplete ly wh ile chaotic sequence is varied synchronously in trans mitte r and re - ceiver. Co mpared to p revious reconfigurab le scheme by t riggered reg ister and switches afte r AWG router, the simulat ion results show that the secret key nu mbe r of proposed cryptog- raphy is significantly inc reased to avoid eavesdropping attack in physical layer. Keywor ds : reconfigurable coded wavelength, tunable wavelength filter array, chaotic sequence, Optical Code-Division Multiple-Access (OCDMA) 1. Introduction The optica l code-div ision mu ltip le -access (OCDMA) techn ique has attracted con sidera - ble attention for the applicat ion in local-a rea networks because it p rovides a burst and asynchronous mult iple-access environ ment in both the time and the spectral domains [1-6]. The recon figu rable sche me was p resented with triggering register and switches config - ured beh ind AW G route r in prev ious wo rk [7]. Howeve r, the t rigge ring varies of reg ister was limited by M-sequence code pattern result ing in few reconfigurab le state. The propos ed cryp - tography is significantly increased while the tunable wavelength filte r a rray is configu red in front of coded AWG router. The proposed encryption/decryption is presented with tunable wavelength filte r array triggered chaotic sequence in section 2. Sect ion 3 eva luates the secret key nu mber o f proposed cryptography to avo id eavesdropper’s attacking in physical laye r. Finally, we p rovide so me concluding remarks and future works . 2. The Proposed Cryptography Con- figured with Random Wavelength Distribution As shown in Fig. 1, the reconfigurable OCDMA-based encryption is designed that the chaos sequence is created non-linear time-variant sequence as secret key and then trigger tunable wavelength filter array as rando m wavelength allocation of broadband light source. The FBG is generally used to play wavelength filter role. In current study, the tunable wav e- length filter array is triggered with chaotic s e- quence. Broadband light source is designed to depend on many varies of tunable wavelength filter array. * Corresponding aut hor. Email: t 10066@cc.kyu.edu.tw Proceedings of Engineering and Technology Innovation , vol. 3, 2016, pp. 04 - 06 5 Copyright © TAETI In the dec rypt ion end sho wn in Fig . 2, symmet ric sche me and ba lanc ed ph o - to-detecto r is presented and recon figurable mechan is m is fo llo wed the enc rypt ion syn- chronously e ithe r pub lic or private channe l . Hence , the mu lt ip le access inte rfe rence (MA I) is c ance lled co mp lete ly wh ile the tunable wave length filte r a rray is trigged by the sa me rando m p ara mete r and in it ia l va lu e of ch aotic sequence chaot ic sequence synchronously in receiver end. Fig. 1 The proposed encryption with tunable wavelength filter array Fig. 2 The proposed decryption with tunable wavelength filter array 3. The Secret Key Evaluation of Proposed Cryptography By s elect ing rando m pa ra mete r and in it ial value o f chaot ic sequence as the secret key to trigger tunable wavelength filter array , many of rando m wave length allocat ions is obtained resulting fro m tunable wave length filte r d is- tribut ion and then the proposed cryptography is imp le mented and chara cterized with the re - configurab le and fle xib le wave length hopping to avoid the tracking easily by eavesdropping. Here , the d istributed pattern L of broadband light source can be possibly assigned and ob - tained by probab ility funct ion o f statistics in Eq . (1). N / M N N M N 2M M L M M M M N! = M!                     (1) where M donates the code length of M-sequence code and provide the usage of M authorized users. N denotes the ma ximu m chipped wave length nu mbe r of broadband light source. Fig. 3 The number of secret key for diffe rent code length Co mpa red to p revious recon figurable scheme by triggered register and s witches be - hind AW G router, the simu lat ion results show that the secret key nu mbe r of proposed cryp- tography is sign ificant ly inc reased shown in Fig . 3. For 63 authorized users’ considerat ion, the inc reasing pe rfo rmance of p roposed scheme is more 10E+36 times than previous scheme [7]. Fig . 3 The eva luation and co mpa rison of the total nu mber of secret key with the proposed wave length filter array and p revious sche me [7]. Proceedings of Engineering and Technology Innovation , vol. 3, 2016, pp. 04 - 06 6 Copyright © TAETI 4. Conclusions Since the OCDMA scheme is characterized with h igher bandwidth and confidentiality, this have much attractive for many researches to enhance the security by increasing the secret key (i.e., code family) of authorized users. The reconfigurable cryptography applied the chaos sequence to create non-linear t ime -variant sequence as secret key and trigger tunable wavelength filter a rray as random wavelength allocation. In addit ion, the AW G router is re - written with ma xima l length code (M-sequence) to act as encoder. Hence, the more rando m wavelength allocations is obtained resulting fro m tunable wavelength filter distribution and imple ment the reconfigurable and fle xib le wavelength hopping to avoid the tracking easily by eavesdropping. Co mpared to previous reconfigurable scheme by triggered register and switches be- hind AWG router, the simu lation results show that the secret key number of proposed cryp- tography is significantly increased to avoid eavesdropper’s attacking in physical layer. For 63 authorized users’ consideration, the increas- ing performance of proposed scheme is more 10E+36 times than previous scheme [7]. Hence, the degree of confidentiality for proposed cryp- tography will be evaluated and verified secure enhancement of the OCDMA scheme in future works. References [1] J. A. Sa lehi, “ Code division mult iple -access techniques in optical fiber networks —part I: fundamental principles,” IEEE Trans. Com- mun., vol. 37, no. 8, pp. 824-833, August 1989. [2] Y. T. Chang, J. F. Huang, C. C. Wang, C. T. Yen, H. C. Cheng, and L. W. Chou, “Adap- tive modified time-spreading and wave- length-group-hopping embedded M-sequence code for improved confidentiality over syn- chronous networks ,” Optical Engineering, vol. 50, no. 5, pp. 055001, May 2011. [3] M. Kavehrad and D. Zaccarin, “Optica l code-division-mu ltip le xed systems based on spectral encoding of noncoherent sources,” J. Lightw. Technol., vol. 13, no. 3, pp. 534-545, March 1995. [4] H. Ta kahashi, K. Oda, H. Toda, and Y. Inoue, “Transmission characteristics of ar- rayed waveguide N × N wavelength mu lt i- ple xer,” J. Lightw. Technol., vol. 13, no. 3, pp. 447-455, March 1995. [5] Z. Wang, J. Chang, and P. R. Prucnal, “Theoretical analysis and experimental in- vestigation on the confidentiality of 2-D incoherent optical CDMA system,” IEEE J. Lightwave Technol., vo l. 28, no. 12, pp. 1761-1769, June 2010. [6] Y. T. Chang and Y. C. Lin, “ Dynamic re - configurable encryption and decryption with chaos/M-sequence mapping algorith m for secure H.264/A VC v ideo streaming over OCDMA passive optical network,” Multimedia Tools and Applicat ion, vol. 74, no. 15, pp. 1931-1948, July 2015. [7] Y. T . Chang, C. C. Sue, and J. F. Huang, “Robust design for reconfigurab le cod- er/decoders to protect against eavesdrop- ping in spectral a mp litude coding optical CDMA networks,” J. Lightw. Technol, vol. 25, no. 8, pp. 1931-1948, Augus t 2007.