Judul: The uses of markov chain in the development of key predictability test methodology
Abstrak: One Time Key (OTK) system with key from alphabetical sequences is one of symmetric encryption algorithm that used in Indonesia to protect secret information until now. Alphabetic sequences in OTK system must be cryptographically secure pseudorandom sequences. OTK system in Indonesia only tested by overlapping m-tuple test developed by Marsaglia (2005). Overlapping m-tuple test doesn’t check the unpredictability of alphabetical sequences, it just tests distribution form and indpendency of alphabetical sequences. So, alphabetical sequences in OTK system cannot be used in cryptography application by the reason of unpredictability sequence is unknown. Because some of Pseudorandom Number Generator (PRNG) algorithm based on block cipher algorithm that has markovian properties, markov chain model used to detect predictability alphabetical sequences. Data in this study consists of two data sources i.e. simulation data that generated from four classes PRNG and OTK system keys in 2005 that used in three communication units of foreign ministry. Simulation data is used to develop key predictability test methodology by find predictability threshold value based on characteristic of match level. OTK system keys will be predictability tested by comparing characteristic of match level with threshold value that is obtained from simulation data. The first result of this study shows the alphabetical sequence generated by first, second and fourth PRNG class can't be modeled with first-order markov chain until third-order. The third PRNG class, except PRNG LCG1, LCG2, coveyou, rand and randu, also can't be modeled with first order markov chain until third-order. Sequence generated by LCG2, coveyou, rand and randu are not fit for use in cryptography because it has a high probability to be modeled by high orders of markov chain (above the order of three). The second result obtains predictability threshold value with markov chains based on the minimum and maximum match level on the second-order and third-order. The last result shows the size of training data must be greater than the size of the observation data with the best ratio between the size of training data with observational data is 100: 10. The results of testing using 10 times repeated shows that the match level average of the OTK system key match on the all of three-order less than 4.5 x 10-2, so the OTK system the is feasible to secure information in three communication units.
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Judul: Kajian Model Hidden Markov Diskret dengan Algoritme Rabiner dan Aplikasinya pada DNA
Abstrak: Setiap kejadian berkaitan erat dengan penyebab kejadian. Jika penyebab kejadian tersebut tidak diamati secara langsung dan membentuk rantai Markov, maka pasangan kejadian dan penyebabnya dapat dimodelkan dengan model Hidden Markov (Hidden Markov Model, HMM). Model Hidden Markov (X, Y) adalah sebuah model yang dibangun oleh rantai Markov X = {Xk;k E N} yang tidak diamati, serta proses observasi Y = {Ykik E N} yang dipengaruhi oleh X. Ciri model Hidden Markov adalah: {X} yaitu sebuah rantai Markov dengan ruang state berhingga Sx = {1,2,...,N} yang homogen dan ergodic. aij = P(Xk+1 = j |Xk = i), untuk i,j = 1,2, ... N. ANXN = (aij) adalah matriks transisi dari X dengan a¿; ≥ 0 N dan Σ=1αij = 1. π; = P(X₁ = j) dengan π = (π1,...,πN). π = E[X] dan memenuhi Aл = π dan Σ=1; = 1. {Ykik E N} yaitu sebuah proses observasi dengan ruang state Sy = {1, 2,..., M}. Proses {Xk, Yk; k E N}, dihubungkan oleh distribusi peluang bersyarat b; (j) = P(Yk = j |Xk = i), j = 1,2, ... M; i = 1,2, ..., N. BNXM = (b)), dengan b; (j) ≥ 0, 1 b; (i) = 1, untuk i = 1,2,..., N. Diasumsikan {YKIXk} saling bebas. Dari ketiga ciri tersebut, diperoleh karakteristik model Hidden Markov yaitu: 2 λ = (A, B, π). Diberikan barisan observasi y₁, Y2, ... Yk; Yk € Sy untuk k = 1,2,..., K dan λ = (A, B, π). Masalah dasar dari model Hidden Markov, yaitu: 1. Menghitung peluang munculnya barisan observasi y1, V2, ... YK- 2. Memilih barisan state yang memaksimumkan peluang observasi. 2. Memilih barisan state yang memaksimumkan peluang observasi. 3. Melakukan pendugaan terhadap parameter-parameter model Hidden Markov λ = (A, B, π), sehingga P(Y₁ = 1, ..., YK = уK2) maksimum. Solusi dari 3 masalah di atas berturut-turut dapat diperoleh dengan algoritme forward, algoritme Viterbi dan algoritme Baum-Welch re-estimation (Rabiner 1989). Didefinisikan peubah forward, a (j) = P(Y₁ = Y1, ..., Yk = Yk, Xk = j|λ). Dengan induksi, ak (j) dapat dihitung sebagai berikut: 1. Inisialisasi: a₁(j) = P(Y₁ = Y₁, X1 = jλ) = πjbj(y1), j = 1,2,... N. 2. Induksi: ak+1) = P(Y₁ = Y1,..., Yk+1 = Yk+1, Xk+1 = jλ) = [=1 αk (i) αij]bj (k+1), j = 1,2, ... N; 1 ≤ k ≤ K − 1. Li=1 3. Terminasi: P(Y₁ = Y1,..., YK = Yk|2) = Σ=1 P(Y₁ = Y1,..., YK = YK, XK = j]) = Σ=1αk(j) K Pada masalah kedua, akan dipilih barisan state {x}=1 sehingga P(Y₁ = y1,..., YK = YK, X1 X1, ..., XK = xx 2) adalah maksimum. Didefinisikan, Sk (j) = maxx1,x2, xk-1 P(Y1 = Y1, ..., Yk = Yk, X1 X1, ..., Xk = j|λ). = Barisan yang menghasilkan (i) yaitu, j) = arg maxi=1,...,N Sk-1 (i)αij......dst
Keyword: Markov chain, discrete hidden Markov model, forward algorithm, Viterbi algorithm, Baum-Welch algorithm

Judul: Peranan Zn-Fitat dalam menyediakan Zn dan pengaruhnya terhadap absorpsi Pb ransum pada domba
Abstrak: Asam fitat banyak terdapat dalam biji-bijian. Senyawa ini dapat mengikat kuat Pb dan Zn. Seng merupakan mineral esensial untuk hewan, tetapi absorpsinya di saluran pencernaan sangat rendah. Suplementasi Zn dapat dilakukan dalam berbagai bentuk.
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