Monitoring the temperature of a computer server room is a critical task to ensure the performance of the server is not disturbed by excessive room temperature. In this paper, we designed and implemented a microcontroller-based room temperature monitoring system using Atmel ATmega8535 microcontroller and National Semiconductor's LM35 temperature sensor. The system is equipped with a Wavecom GSM modem to send and receive text message (SMS) and relay board to control electronic equipment. The experiment results show that our system works as expected. The system raises an alarm and send an alert message to administrator when the room temperature is above threshold, which is 28°C. General Terms Design, Experimentation KeywordsMicrocontroller, temperature sensor, server room temperature

Paper-based documents or printed documents such as recommendation letters, academic transcripts, and diplomas are prone to forgery. Several methods have been used to protect them, such as watermarking, security holograms, or using paper with specific security features. This paper presents a document authentication system that utilizes QR code and ECDSA as the digital signature algorithm to protect this kind of document from counterfeiting. A digital signature is a well-known technique in modern cryptography used for providing data integrity and authentication. The idea proposed herein is to put a QR code in the printed documents where the QR code includes a digital signature. The signature can later be authenticated using the proposed system by uploading the document for authentication or scanning the document's QR code. The proposed system is particularly developed for digital signature generation and verification of students' final project approval documents as the case study. In traditional settings, the approval form is typically signed directly by the student's advisor dan co-advisor using handwritten signatures. However, using the conventional handwritten signature, the signature on the approval form can be falsified. Therefore, a digital signature generation and verification system is implemented herein to avoid handwritten signature falsification. The advisors can use this system to sign the approval form using a digital signature instead of a handwritten one. The signature is stored in a QR code and is generated using ECDSA with SHA-256 as the hash function. The proposed system is evaluated using documents (i.e., approval forms) with genuine and forged QR codes.  The evaluation results showed that the system could verify the authenticity of the approval forms, which contain genuine QR codes. The approval forms that contained forged QR codes were correctly identified.

The authenticity and integrity of documents are essential in data exchange and communication. Digital documents must be verifiable for their authenticity and integrity by all parties that use the documents. Generally, digital documents can be authenticated by using digital signatures. This study aims to implement a document authentication system based on Quick Response (QR) code and digital signature. As the case study, the document authentication system is implemented to generate digital signatures for student’s certificate documents. Furthermore, the system can also verify the authenticity of the certificate documents. Creating a digital signature requires a hash function algorithm for generating the message digest of the document. In addition, an algorithm to generate the public key and the private key used in the encryption/decryption of the message digest is also needed. The hash function utilized in this study is the Secure Hash Algorithm-256 (SHA-256), while the algorithm used for encryption/decryption is the Rivest-Shamir-Adleman (RSA) algorithm. The system is evaluated by verifying 30 student certificate documents, of which 15 of them were certificates with QR code signature generated by the system and the other 15 were certificates with QR code signature generated using a random QR code generator. The system’s testing results demonstrate that the system can ensure the authenticity and integrity of the signed certificate documents to prevent document falsification. All documents that contain random QR codes were correctly identified as false documents.

Pola berulang dan simetris berdimensi dua sering dijumpai dalam kehidupan sehari-hari, seperti pada motif kain, paving jalan, barisan tapak kaki seseorang di pasir. Pola berulang dan simetris tersebut terbentuk dari transformasi, yang terdiri dari translasi, rotasi, refleksi, dan refleksi-glide. Dalam matematika, pola berulang dan simetris pada bidang datar, yang terbentuk dari transformasi, termasuk dalam grup simetri bidang datar. Grup simetri bidang datar ini sering disebut juga sebagai grup kristalografi bidang datar atau grup kertas dinding (wallpaper group). Terdapat 17 grup kertas dinding yang dikenal. Tujuan dari penelitian ini adalah membangkitkan berbagai macam pola dari suatu pola dasar dengan menerapkan konsep grup kertas dinding. Penelitian dilakukan dengan (1) menentukan dan membuat suatu pola dasar yang digunakan untuk membentuk pola lain, (2) membangkitkan 17 pola yang dibentuk dari 17 grup kertas dinding, dan (3) mengidentifikasi pola gambar yang diperoleh dari internet termasuk ke dalam salah satu grup kertas dinding. Pola dasar yang digunakan dalam penelitian ini adalah spiral. Hasil yang didapat berupa 17 motif spiral yang berbeda dan juga empat motif yang diambil dari internet yang dapat dikenali sebagai salah satu pola dari 17 pola grup kertas dinding.

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