Java Security

Java provides a robust security model to protect both the Java runtime environment and applications running within it. Java’s security features are designed to prevent unauthorized access, ensure data integrity, and maintain the overall safety of Java applications.

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Tutorials

Base64 file encoding and decoding in Java, file bytes read with Files.readAllBytes, encoded by Base64.Encoder into ASCII text that is about 33 percent larger, carried in JSON or email, and decoded by Base64.Decoder back into identical bytes

Java Base64 Encode and Decode a File (Text, Image, Large Files)

Base64 encode and decode a file in Java with examples for text and image files, data URIs, streaming large files with wrap(), MIME and decoding errors.

JSON Web Token (JWT) Explained With Java jjwt Examples

Learn how a JSON Web Token (JWT) works, create and validate one with jjwt 0.13 and nimbus-jose-jwt, and avoid the storage, key and expiry mistakes.

Java Core & Fundamentals Tutorial

Java tutorial for beginners on Java 25. Install the JDK, run a first program and follow a 12-step learning path plus an index of every Java topic.

Java EdDSA Example: Sign and Verify With Ed25519 and Ed448

Java EdDSA example with Ed25519 and Ed448. Generate keys, sign and verify messages, save and load keys, and compare EdDSA with ECDSA, RSA and ML-DSA.

Secure Random Number Generation in Java with SecureRandom

Secure random number generation in Java with SecureRandom. Create tokens and codes, pick NativePRNG, DRBG or getInstanceStrong and avoid seeding mistakes.

Java AES Encryption and Decryption: AES-256-GCM Example

Java AES encryption and decryption with AES-256-GCM, random IVs, key storage, PBKDF2 and HKDF keys, file encryption, tamper detection and common mistakes.

SSLHandshakeException in Java: Fix TLS 1.2 Handshake Errors

SSLHandshakeException means the Java client and the server could not agree on a TLS connection. Fix TLS version mismatches with jdk.tls.client.protocols, untrusted certificates with keytool, and find the rest with javax.net.debug.

Bypass SSL Certificate Checking in Java (and Safer Fixes)

Bypass SSL certificate checking in Java only in local tests, and fix PKIX errors safely with a truststore, a trusted PEM certificate or Spring SSL bundles.

REST API Security Guide: Checklist With OWASP API Top 10

A current REST API security checklist with OAuth 2.1, JWT validation, TLS, authorization checks, input validation, rate limiting and OWASP API Top 10.

Set Windows Environment Variables Without Admin Rights

Set Windows environment variables without admin rights using the account dialog, setx or PowerShell, and fix JAVA_HOME and Path for Java on locked laptops.

Java File Checksum: MD5 and SHA-256 Hash Examples

Java file checksum examples for MD5 and SHA-256 with MessageDigest, streaming for large files, HexFormat, Guava, Commons Codec and verifying downloads.

Java Base64 Encode and Decode (Basic, URL-Safe and MIME)

Java Base64 encode and decode examples with java.util.Base64 for strings, URL-safe tokens, MIME email, files and streams, plus fixes for decoding errors.

Java Password Hashing: MD5, SHA, PBKDF2, bcrypt and Argon2

Java password hashing done right with PBKDF2, bcrypt, scrypt and Argon2id, OWASP parameters, salts, real timings, and why MD5 and SHA-256 fail.