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All Journal JOURNAL OF APPLIED INFORMATICS AND COMPUTING
Budi Handoko
Universitas Dian Nuswantoro
Computer Science & IT

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Integrated Cryptographic Framework berbasis AES-256, RSA-2048, dan Blind Signature untuk Secure E-Voting Model Justin Matthew Triono; Eko Hari Rachmawanto; Azriel Sebastian Pamungkas; Budi Handoko
Journal of Applied Informatics and Computing Vol. 10 No. 5 (2026): October 2026
Publisher : Politeknik Negeri Batam

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.30871/jaic.v10i5.13641

Abstract

Electronic voting (e-voting) is presented as a digital solution to replace the conventional election system where the process of recording, storing, and calculating voter vote data will be done digitally, with the aim of accelerating the vote recapitulation process and minimizing human errors. In its implementation, strict security guarantees are required for crucial aspects such as voter anonymity and vote integrity from manipulation in its implementation. To address these challenges, this study proposes a network-based e-voting model integrated with four cryptographic pillars: the AES-256 algorithm used to encrypt vote data symmetrically and ensure the confidentiality of each individual's choices efficiently; the RSA-2048 algorithm, an asymmetric cryptographic system used to secure AES key exchange and provide authentication for each data transaction; and the Blind Signature scheme that allows the server to verify and sign votes without knowing their contents, thus effectively separating the voter's identity from his or her choice. Experimental results show that the proposed system successfully meets five fundamental security properties: anonymity (deanonymization probability ≈ 1/2²⁰⁴⁸ ≈ 3.23 × 10⁻⁶¹⁷), integrity (100% manipulation detection rate via HMAC-SHA256), confidentiality (via AES-256-CBC double encryption), legitimacy (via voter registration verification), and singleness (100% prevention of duplicate voting). Performance evaluations show an average processing time of 763 milliseconds per voter, confirming that the level of cryptographic security does not compromise the overall system responsiveness. With this architecture, the proposed model not only promises a more efficient election process but also increases the level of public trust through a transparent and cryptographically secure system.
Digital Signature Implementation Using RSA and SHA-256 Algorithms for Authenticity Verification of Digital Certificate Images Hezzekia Rafael Miracle; Christy Atika Sari; Budi Handoko
Journal of Applied Informatics and Computing Vol. 10 No. 5 (2026): October 2026
Publisher : Politeknik Negeri Batam

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.30871/jaic.v10i5.13886

Abstract

The need for a system capable of accurately and rapidly verifying academic documents is crucial for ensuring the authenticity of digital certificates. This research implements a digital signature mechanism within the ECert Verify (Electronic Certificate Verification) system, utilizing the RSA-2048 algorithm alongside the PSS (Probabilistic Signature Scheme) padding scheme and the SHA-256 hash function to authenticate digital certificate images from Coursera. Each certificate is automatically converted into a 300 DPI (3508×2480 pixel) grayscale image to maintain hash consistency. The system was developed using Python with the pyca/cryptography library, Django for the backend, and React (Vite) for the frontend. Testing involved 20 datasets, comprising 5 authentic certificates and 15 manipulated samples (involving screenshots, re-compression, and content modification). Test results demonstrated a 100% verification accuracy rate, with no instances of false positives or false negatives. An average Avalanche Effect of 50.88% indicates that SHA-256 is highly sensitive to minor changes in the certificate image. Shannon Entropy testing yielded an average value of 7.1786 bits (89.73%)—close to the theoretical maximum of 8.0 bits—demonstrating a high level of randomness in the generated digital signatures. The average verification time was just 2.46 ms per file, indicating strong performance in a controlled single-user testing environment. Furthermore, a limited user acceptance survey regarding the interface's operational aspects revealed that the system is highly rated and functional in supporting the certificate issuance process for operators.
Analysis of Chaos-Based Cryptography Using Logistic Map and Arnold’s Cat Map for Digital Image Encryption Sulthan Yustr Suwardhi; Budi Handoko; Eko Hari Rachmawanto
Journal of Applied Informatics and Computing Vol. 10 No. 5 (2026): October 2026
Publisher : Politeknik Negeri Batam

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.30871/jaic.v10i5.14079

Abstract

Medical images transmitted over public networks are vulnerable to interception because of their large volume and strong spatial correlation among neighboring pixels. Conventional ciphers such as AES are not specifically designed for this redundancy and may leave residual statistical structure when applied directly to images. This study evaluates a hybrid chaos-based image encryption scheme that combines Arnold’s Cat Map for pixel-position confusion with the Logistic Map for value diffusion. Instead of introducing an additional chaotic map, the diffusion stage is strengthened using a double-pass cipher-block chaining (CBC) mechanism with modulo addition. The method was tested on 20 grayscale brain-tumor images (256×256 pixels) from a public medical dataset. Security was assessed using histogram analysis, adjacent-pixel correlation, information entropy, differential NPCR and UACI, key sensitivity analysis, and execution time. A baseline ACM–Logistic XOR scheme was also compared under the same key parameters. The proposed CBC-enhanced scheme achieved an average encrypted-image entropy of 7.997, correlation coefficients close to zero, differential NPCR of 99.35%, and differential UACI of 32.84%. Key sensitivity tests yielded NPCR values above 99.6% for perturbations of the logistic parameters as small as 10-14, and multi-delta analysis confirmed stable avalanche behavior down to 10-15. Decryption with the correct key recovered all images without pixel loss. These results indicate that double-pass CBC can improve differential diffusion in a lightweight two-map architecture suitable for protecting grayscale medical images.
Co-Authors Azriel Sebastian Pamungkas Christy Atika Sari Eko Hari Rachmawanto Hezzekia Rafael Miracle Justin Matthew Triono Sulthan Yustr Suwardhi