The rapid development of information technology has made it easier to access various sources of information, but it has also increased the risk of plagiarism, especially among university students. To maintain academic integrity and the quality of education, plagiarism detection is essential. This study aims to develop a plagiarism detection system using the Knuth-Morris-Pratt (KMP) algorithm combined with the Jaccard Similarity method to measure the similarity between documents. The system is designed to analyze Indonesian-language essay documents in Word (.docx) and PDF (.pdf) formats that do not contain images or tables. The detection process begins with data preprocessing steps, including case folding, tokenizing, stopword removal, and stemming, to enhance efficiency and accuracy. The system is developed using the Python programming language and the Flask framework. Test results show that the system can detect plagiarism with an average accuracy of 98.66%. The level of similarity between documents is then categorized into three levels: Minor, Moderate, and Severe Plagiarism. This system is expected to serve as an effective tool in minimizing plagiarism practices in higher education and supporting the creation of an honest and responsible academic culture.

Keamanan data transaksi merupakan aspek krusial dalam sistem e-commerce, khususnya bagi pelaku usaha kecil menengah (UMKM). Penelitian ini bertujuan untuk mengimplementasikan algoritma Blowfish dengan mode Cipher Block Chaining (CBC) dan panjang kunci 160-bit guna meningkatkan keamanan data transaksi penjualan. Algoritma Blowfish dipilih karena efisien dan mendukung penggunaan Initialization Vector (IV) acak yang memperkuat proteksi terhadap serangan pattern dan dictionary. Data transaksi pelanggan dan pembayaran disimpan dalam bentuk ciphertext menggunakan OpenSSL. Pengujian dilakukan terhadap 20 data transaksi menggunakan serangan dictionary berbasis OpenSSL, dan hasil menunjukkan bahwa data tidak dapat didekripsi, membuktikan efektivitas pendekatan ini. Hasil penelitian ini menunjukkan bahwa penggunaan Blowfish CBC 160-bit dengan IV acak mampu memberikan perlindungan kuat dan efisien dalam konteks aplikasi e-commerce untuk UMKM.
Kata kunci: Keamanan Data Transaksi, Blowfish CBC, Initialization Vector, E-Commerce, Dictionary Attack

Marketplace system is a means of meeting sellers and buyers online, in this case service providers and car renters. With this information system, renters no longer need to bother looking for the required car that matches the criteria, and service providers are also easier in marketing and expanding their marketing reach. This system was built using the RAD (Rapid Application Development) method of development which allows customers to place orders, select vehicles, eliminating complexity in the traditional process involving visits to rentals. In car rental services there are several problems that need to be resolved. First, there is no web-based information system service that makes it easy for customers to access car rental service company information. Second, conventional services are still fairly slow. Currently, reservations are made in two ways, namely coming to the place or contacting the telephone number on Whatsapp so that prospective tenants have to wait for a response from the rental provider to get information about prices and available cars. Therefore, a car rental information system is needed that specifically serves fleet rental with online booking to display transaction information in the form of car rental and return on the system dashboard to support strategic purposes. This research focuses on building a car rental information system using the PHP programming language with the CodeIgniter framework.