Judul: Protokol Keamanan Dokumen Digital pada Sistem E-Procurement menggunakan AES, RSA, dan SHA1
Abstrak: Digital signature is an authentic evidence and also has a function like a signature on the printed document, but its use in digital documents. Documents that was sent through the internet, should be ensured their source and destination. This research is decided to implement a security protokol on file transfer process on e-procurement system using AES, RSA, and SHA1 algorithm. Data used in this research is a compressed digital document with ZIP format. The result of this research indicate that the system has been created already capable of generating and verify digital signature. The security services that owned by this system such as confidentiality, entity authentication, data origin authentication, integrity, and non repudiation. The testing process is performed on these security services including confidentiality test, authentication test, integrity test, and non repudiation test. Confidentiality is guaranteed by the encryption process using AES algorithm. In addition, authentication, integrity, and non repudiation service is guaranteed by the digital signature mechanism.
Keyword: Bogor Agricultural University (IPB), tender, digital signature, E-Procurement

Judul: Protokol legalisasi digital menggunakan algoritme MD5 dan RSA
Abstrak: The need for legalization of certificate diplomas and transcripts to apply for a job is a reasonable requirement, but sometimes the collection deadline given is very short. Noting the need for rapid validation system for the legalization of certificate diplomas and transcripts, a securing system that can legalize and give legitimacy to the diploma and transcript is needed. One of these mechanisms is digital signatures. This research applied MD5 and RSA to create digital signatures of certificate diplomas and transcripts. MD5 is a function that processes an arbitrary length inputs into outputs with a fixed length, ie 128 bits. RSA is an encryption-decryption asymmetric algorithm. The key used to encrypt a plaintext differs from the key used to decrypt the ciphertext into its original plaintext. Digital signatures generated from the plaintext by using the MD5 algorithm is then encrypted using the RSA algorithm. The result of RSA encryption called digital signatures. The implementation of digital signatures can shorten the time digital legalization of certificate diplomas and transcripts and ensure the security and validity of information
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Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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