Judul: Protokol Pertukaran Kunci Berbasis Kriptosistem Kunci Publik Elgamal.
Abstrak: Komunikasi atau pertukaran data sekarang ini sangat mudah dilakukan bahkan komunikasi jarak jauh sekalipun. Namun kemudahan ini tidak hanya membawa dampak positif tetapi juga negatif, salah satunya adalah keamanan datadata yang dipertukarkan tersebut. Data tersebut harus dienkripsi menjadi pesan rahasia agar tidak seorang pun, selain party yang berkomunikasi, dapat mengetahui isi pesan rahasia tersebut. Kriptosistem pertukaran kunci publik ElGamal merupakan salah satu metode yang dapat digunakan untuk pengamanan tersebut. Karya ilmiah ini menjelaskan teori-teori yang digunakan dalam protokol pertukaran kunci berbasis kriptosistem kunci publik ElGamal, mekanisme protokol tersebut dan menganalisis keamanan dari kriptosistem kunci publik ElGamal. Party-party yang berkomunikasi akan membuat sebuah kunci rahasia atau kunci sesi dengan pertukaran kunci publik. Setelah pertukaran tersebut, party-party akan memeroleh kunci rahasia atau kunci sesi yang akan digunakan untuk mengenkripsi dan dekripsi data. Kriptosistem kunci publik ElGamal dapat dikatakan cukup aman karena adanya masalah logaritma diskret dan proses autentikasi yang mencegah terjadinya man-in-the-middle attack.
Keyword: ElGamal, komunikasi, kriptosistem, kunci rahasia

Judul: Protokol Pertukaran Kunci Berbasis Kriptosistem Kunci Publik Diffie-Hellman
Abstrak: Karya ilmiah ini menjelaskan teori-teori yang digunakan dalam protokol pertukaran kunci berbasis kriptosistem kunci publik Diffie-Hellman, mekanisme protokol tersebut dan menganalisis keamanan dari kriptosistem kunci publik Diffie-Hellman. Algoritme Diffie-Hellman merupakan salah satu protokol komunikasi dengan sistem kriptografi kunci asimetri atau kunci publik. Algoritma ini digunakan untuk mempertukarkan kunci rahasia bersama (kunci rahasia yang digunakan untuk komunikasi dengan menggunakan sistem kriptografi simetri) antara dua orang atau lebih. Tingkat keamanan dari algoritme Diffie-Hellman didasarkan pada masalah logaritma diskret bagi grup pergandaan bilangan bulat modulo prima. Karena tidak adanya proses autentifikasi dalam algoritme Diffie- Hellman, mengakibatkan algoritme ini rentan terhadap ancaman dari penyerang aktif dalam proses pertukaran kunci.
Keyword: Diffie-Hellman, kunci publik, kunci rahasia bersama, masalah logaritma diskret, pertukaran kunci

Judul: Thermal Characteristics and Dynamics of Tropical Cyclone over Western North Pacific Ocean: A Case Study of Typhoon Songda (Chedeng) 2011
Abstrak: The frequent occasion of Tropical Cyclone (TC) over Western North Pacific (WNP) Ocean lies from 10˚N to 26˚N and 121˚E to 170˚E. Sources of TC development come from warm ocean temperature where latent heat is released during condensation processes and subsequently concentrated in the boundary layer. Relative humidity at 850-700 hPa is responsible to produce the most intense storm. Meanwhile, weak vertical wind shear between 850-200 hPa is one of the dynamical factors that lead to the development of TC. Pressure level of 850-200 hPa is chosen to minimize the thermodynamic effect in the lower troposphere. Typhoon Songda (Chedeng in the Philippines) or TSC lasted from May 18th to 30th, 2011 and strengthened into powerful Super Typhoon stage between May 24th and 27th. Long curving track and the exhibition of all sequences of TC life cycle, TSC is then considered as an ideal case of TC. The objective of the study with case of TSC is to investigate the role of thermal characteristics and dynamics on TC intensity. The research is carried out by using Advanced Research of Weather Research and Forecasting model (WRF ARW model) version 3.3. Two domains are employed in the model. The first domain situate from 02˚N to 40˚N and 118˚E to 149˚E and cover spatial resolution () of 33.1 km. The second domain situate from 09˚N to 27˚N and 119˚E to 132˚E with of 11 km. Timestep of the model () is 120 seconds. The model is supported by the following physical parameterization, i.e., Yonsei University Scheme (YSU) in the boundary layer, Kain-Fritsch scheme (KF) in the cumulus, and WRF Single-Moment 3-class scheme in the microphysics. Initial meteorological condition prior to the formation of the cyclone is generated using WRF ARW standard-release model. Sensitivity of the model output is obtained from a selected single-parameter change scenarios, namely, 10 % to 20 % decrease and increase of wind shear initial data at 850-200 hPa, and by 10 % to 20 % decrease of relative humidity initial data at 850-700 hPa. The result showed that the negative correlations between wind shear and intensity are found in wind shear scenarios. Wind shears of 10 ms-1 which lead to strengthening of the wind intensity in the early period of Typhoon development are found in wind shear scenarios. The effect of wind shear changes on wind intensity is statistically significant in the 20 % wind shear scenarios. During mature stage, weak wind intensity occurred when wind shear increase as given in the WRF standard-release and the 20 % decreasing scenario. Different situation is found in the 20 % increasing scenario where wind shear tend to weak and lead to strong wind intensity at this stage. Meanwhile, the reduction of moisture supply at 850-700 hPa resulting from 20 % decreasing relative humidity play a major role in the weakening of wind intensity and reduces mechanical energy of the cycle process as much as 300 J kg-1.
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