COTP — Cell-based One-Time Password

Zero-dependency Java library for COTP: a deterministic, printable 5×5 challenge-card authentication factor, built as an analog of the Avatier Identity Challenge Card.

• Java library: cotp-java/ — see cotp-java/README.md for the full overview, build instructions and API quick start.
• Specification: COTP_SPECIFICATION.md
• Integration guide: INTEGRATION_GUIDE.md + runnable example examples/IntegrationExample.java.
• Metrics module: cotp-metrics/ (optional, Micrometer).
• PDF/QR card template: cotp-pdf/ (optional, PDFBox + ZXing).
• Distributed state stores: cotp-jdbc/ (DataSource) and cotp-redis/ (Lettuce); shared contract in cotp-store-contract/.
• Web demo: cotp-demo/ (JDK HTTP server, no dependencies).
• Security & ops: docs/THREAT_MODEL.md, docs/OPERATIONS_RUNBOOK.md, docs/SEQUENCE_DIAGRAMS.md.
• Roadmap / backlog: TODO.md

Quick start

Build and verify the library with the bundled Maven Wrapper (requires JDK 17+):

./cotp-java/mvnw -f cotp-java/pom.xml verify

On Windows:

.\cotp-java\mvnw.cmd -f cotp-java\pom.xml verify

Or, without Maven at all, run the dependency-free self-test:

powershell -ExecutionPolicy Bypass -File .\cotp-java\run-verify.ps1

Requirements

• JDK 17 or newer.
• No runtime dependencies (the library uses only the JDK).

License

MIT — see LICENSE. Copyright (c) 2026 COTP project.