This repository is a Java library for JSON Web Token (JWT) handling per RFC 7519. It provides comprehensive functionality for creating, signing, verifying, and decoding JWTs, supporting multiple cryptographic algorithms including HMAC (HS256/384/512), RSA (RS256/384/512, PS256/384/512), EC (ES256/384/512), and EdDSA (Ed25519/Ed448). The library also includes utilities for JSON Web Key (JWK) management, PEM encoding/decoding of keys and certificates, and ASN.1 DER parsing for low-level cryptographic operations. Architecturally, the library follows a modular structure with clear separation of concerns: core JWT operations in the `jwt` package, JWK handling in `jwks`, PEM utilities in `pem`, and DER parsing in `der`. Cryptographic operations are abstracted through `Signer` and `Verifier` interfaces, enabling the Strategy pattern for pluggable algorithm implementations. Object creation uses the Builder pattern for immutable, fluent APIs (e.g., `JWT.addClaim()`, `KeyPair.build()`). JSON processing is centralized via a configured Jackson `Mapper` with custom serializers/deserializers for Java 8+ date-time types. The design minimizes coupling, allowing components like `JWTUtils` or `HMACSigner` to be reused independently. The library is actively maintained, with recent commits (2026-07-15) and ongoing security updates (e.g., patches for CVE-2022-21449). Dependencies are managed via Maven/Savant, relying primarily on Jackson for JSON processing with optional Bouncy Castle for certain algorithms. The codebase demonstrates strong engineering practices: comprehensive unit tests cover all algorithms and edge cases, clear exception hierarchies provide specific error handling, and Java 9+ module system support is included. It serves as a robust, reusable foundation for any Java application requiring secure token-based authentication or authorization.