Building CivicGemma: A Tamper-Evident E-Voting Microservices Platform with Gemma 4 🗳️

A developer built CivicGemma, an open-source microservices e-voting pilot for local body elections, combining Java 21 and Spring Boot 3.4.2 services, an Angular 22 frontend, and Google's open-weights Gemma 4 multimodal model. The platform uses a database-per-service architecture with a compound unique index and SHA-256 ballot sealing to prevent double voting and produce tamper-evident receipts, while Gemma 4 handles voter ID image verification and multilingual manifesto summaries in English, Hindi, and Odia.

During Hacktoberfest Hack Day Bhubaneswar × DatrixLabs , I built CivicGemma — an open-source, full-stack microservices e-voting pilot system designed specifically for local body elections Panchayats, Municipalities, and Wards . It combines Java 21 & Spring Boot 3.4 microservices , Angular 22 , and Gemma 4 multimodal AI to deliver double-voting prevention, cryptographic SHA-256 ballot sealing, and multilingual voter assistance. Grassroots democracy is where policy directly impacts daily life — from local roads to sanitation and water supply. However, local body elections face unique logistical hurdles: We asked: Can we build a transparent, auditable, and accessible digital voting platform that guarantees ballot integrity while empowering voters with AI? That was the birth of CivicGemma . Rather than building a monolithic prototype, we architected CivicGemma around the Database-per-Service pattern using Spring Cloud 2024 and Spring Boot 3.4.2 : ┌─────────────────────────┐ │ Angular 22 Frontend │ └────────────┬────────────┘ │ HTTP / REST ▼ ┌─────────────────────────┐ │ Spring Cloud Gateway │ Port 8080 └────────────┬────────────┘ │ lb:// ┌──────────────┬─────────────┼─────────────┬──────────────┐ ▼ ▼ ▼ ▼ ▼ ┌──────────────┐┌────────────┐┌────────────┐┌────────────┐┌────────────┐ │ Auth Service ││Voter Service││Voting Service│Result Service│Audit Service│ │ Port 8086 ││ Port 8081 ││ Port 8084 ││ Port 8085 ││ Port 8087 │ └──────┬───────┘└─────┬──────┘└─────┬──────┘└─────┬──────┘└─────┬──────┘ │ │ │ │ │ Auth DB Voter DB Voting DB Result DB Audit DB Auth , Voter , Election , Candidate , Voting , Result , and Audit . In electronic voting, preventing race conditions e.g., clicking "Vote" simultaneously across multiple tabs is paramount. We implemented a three-tier defense : if voteRepository.existsByElectionIdAndVoterId dto.getElectionId , dto.getVoterId { throw new IllegalStateException "Voter has already cast a ballot." ; } Database Engine Constraint The Hard Wall : We enforce a compound unique index constraint at the database level: ALTER TABLE votes ADD CONSTRAINT uk election voter UNIQUE election id, voter id ; Cryptographic SHA-256 Ballot Sealing: Every ballot generates a tamper-evident digital seal returned to the voter as a verifiable receipt: String rawData = voterId + ":" + electionId + ":" + candidateId + ":" + timestamp + ":" + UUID.randomUUID ; MessageDigest digest = MessageDigest.getInstance "SHA-256" ; byte hashBytes = digest.digest rawData.getBytes StandardCharsets.UTF 8 ; // Returns 64-character hexadecimal receipt hash 🤖 Core Innovation 2: Gemma 4 Multimodal Civic AI We leveraged Google's open-weights Gemma 4 model to solve two real-world accessibility challenges: 1. Multimodal Voter ID EPIC Verification Elderly or rural voters can upload an image of their Electors Photo Identity Card EPIC . Gemma 4's vision capabilities inspect the card, verify document legibility, extract the identifier, and cross-validate with the voter-service registry. 2. Multilingual Manifesto Explainer Local voters can ask natural language questions in English, Hindi, or Odia: "Who is running in Ward 12?" "Summarize Candidate Arjun Sharma's key promises in 3 bullet points." "Which candidate has promised better water drainage?" Gemma parses structured candidate manifestos and delivers impartial, concise summaries. 🛠️ The Tech Stack Domain Technologies Backend Java 21 LTS, Spring Boot 3.4.2, Spring Cloud 2024 Eureka, Gateway, OpenFeign Frontend Angular 22 Standalone Components, SSR, Tailwind CSS Databases MySQL Isolated schema per microservice AI / ML Google Gemma 4 / Gemini API Security Stateless JWT HMAC-SHA256 , BCrypt, SHA-256 DevOps Maven Multi-Module, Automated Batch Launchers start-all.bat 🧗 Challenges Faced & Lessons Learned 1. The JDK Compiler vs. Lombok Dilemma During compilation, we hit a compiler error: Fatal error compiling: java.lang.ExceptionInInitializerError: com.sun.tools.javac.code.TypeTag :: UNKNOWN We discovered that the host environment was compiling with bleeding-edge JDK 25/26, which introduced breaking internal changes to com.sun.tools.javac.code.TypeTag that broke annotation processors like Lombok. We diagnosed and resolved this by pinning our toolchain to Eclipse Temurin JDK 21 LTS, restoring clean, reproducible builds. 2. Distributed State vs. Network Partitions When voting-service records a ballot, it must sync hasVoted = true with voter-service. While OpenFeign handles synchronous calls gracefully, a network partition requires resilience. We architected fallback exception handlers and designed the schema so that the ballot ledger remains authoritative even if the voter metadata service experiences latency. 🔮 What's Next for CivicGemma? Zero-Knowledge Proofs ZKP : Implementing zk-SNARKs to achieve complete ballot unlinkability while mathematically guaranteeing eligibility. Consortium Blockchain Hyperledger Fabric : Moving the audit log service onto a distributed ledger so no single administrative authority can modify election logs. Offline Polling Station Sync: Edge-caching for rural booths with intermittent connectivity. 🙏 Acknowledgements Huge thanks to Major League Hacking MLH , DatrixLabs, and the Hacktoberfest community for organizing this hackathon GitHub Repository: https://github.com/hira8969/E-Voting-Pilot-System-for-Local-Body-Elections Live Demo Video / Project Link: https://lnkd.in/p/dKgcisNt Drop a ❤️ if you found this interesting, and leave your thoughts on digital voting in the comments --- 4. Optional Polish: - Cover Image: You can click the ✨ Generate Image button at the top to let DEV generate an AI cover banner for your post. - Preview: Click the Preview tab next to "Edit" to see how clean the article looks before publishing. - Click Publish blue button at the bottom left when you're ready