Judul: Analisis Beragam Skenario Enkripsi pada Gambar Digital Berwarna Menggunakan Algoritme Data Encryption Standard (DES)
Abstrak: Cryptographic techniques are widely applied to maintain the confidentiality of a message. However, most cryptographic techniques are currently still being performed on the entire content of the message, so that they require high computation time. Therefore, in this research we designed several test scenarios to encrypt partially the contents of the messages which can lead to faster computation while still maintaining the quality of information confidentiality. In this research, we used BMP image files of digital color photographs with color depth 24-bit consisting of three different objects. Encryption technique used is Data Encryption Standard (DES) with operating mode Electronic Codebook (ECB). Analysis is performed on computation time and quality of the encryption of each scenario. The quality of encryption is computed using Peak Signal to Noise Ratio (PSNR) and a survey to 30 respondents. Respondents will compare the original image file (plaintext) and encrypted image (ciphertext). Results of the analysis showed that the computation time is not only affected by the resolution of image files but also by the choice of the encryption scenarios. The encryption with the best, indicated by the smallest PSNR values was generated by the scenario 1 (scenario full) with the average value of 33,62 dB, while the largest PSNR value was generated on the scenario 8 (head section) with an average value of 39,67 dB. Encryption quality visually assessed based on the results of the survey. The results of the survey concluded that, the best encryption quality was achieved in scenario 1 with a value of 93,33%, and the worst in scenario 7 (bottom scenario) with a value of 28%. In this research, the computation time of scenario 8 is one third of the computation time of scenario 1. Conclusions obtained from this research is that by applying the appropriate encryption scenario, shorter computation time can be achived while maintaining effective encryption.
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Judul: ROSANJA. Combining Data Compression Techniques and Stream Ciphers Encryption for Digital Image Security.
Abstrak: One of the most common information form is image. Some certain images are strictly confidential, therefore, it has to be kept confidential. The process of maintaining its confidentiality is related to cryptography. Cryptography has two main components, encryption and decryption. In many cases, confidentiality is not the only issue, but also how the data is stored and transferred. To solve these issues, data compression is required. The purpose of this research is to apply data compression techniques and stream ciphers encryption for digital image, and to analyze the result. This research uses DCT method and quantization with compression level 50 (in 1-100 scale). LFSR method is used to generate a key. Then, PSNR value of the decrypted image is calculated. As a result, this research shows that the compression process affects encryption time, the time required to encrypt and decrypt an image is getting longer as the size of the image grows.
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Judul: Revisi Marga Maotia Wedd. (Urticacae) di Malesia
Abstrak: A taxonomic revision of genus Maozrtia in Malesia has been done. At present revision, 6 species are recognized namely M. ambigua, M. diversifolia, M. lanceolata, M. platistigma, M puya, and M. setosa. M ambigua is divided into 7 varieties, which one of the variety (i.e. var. tomentosa) n ew to science and another (i.e. var. grandifolia) is a new combination based on M. grandifolia. Two new varieties w i t h M. diversivolia (namely var. novoguinesis and var. suniatrana) are proposed. M. gracilis is recognized here as a synonim 0f M. lanceolata.
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