What is JKS?

JKS (Java KeyStore) is Java's binary keystore format - repository for cryptographic keys and certificates. Managed by Java Keytool command-line utility. Stores: private key entries (SSL/TLS keys + certificate chains), trusted certificate entries (CA roots). Password-protected (entire keystore + individual key passwords). Proprietary to Java - not compatible with other languages/platforms without conversion. Common in Java web servers (Tomcat, Jetty, WildFly), Spring Boot applications, Android app signing.

JKS files are essential for Java HTTPS - configure Tomcat server.xml with keystore path + password. Every Spring Boot HTTPS app uses JKS (or PKCS12 alternative). Create JKS with keytool: generate keypairs, import certificates, list entries. Two entry types: PrivateKeyEntry (private key + cert chain for SSL servers), TrustedCertEntry (CA certificates for validating others). Android apps historically used JKS for APK signing (now migrating to PKCS12). Major limitation: proprietary format - Oracle deprecated JKS in Java 9, recommending PKCS12 instead. However, JKS still widely used in existing Java infrastructure.

Did you know? JKS is deprecated since Java 9 - migrate to PKCS12 for better compatibility!

History

Sun Microsystems created JKS as Java's native keystore format, becoming standard for Java SSL/TLS until deprecation in favor of PKCS12.

Key Milestones

  • 1995: Java 1.0 with keytool
  • 1999: Tomcat SSL support
  • 2000s: Enterprise Java standard
  • 2014: Spring Boot adoption
  • 2017: Deprecated in Java 9 (PKCS12 preferred)
  • Present: Legacy format (still widely used)

Key Features

Core Capabilities

  • Java Native: Keytool integration
  • Dual Storage: Private keys + trusted CAs
  • Password Protection: Keystore + individual keys
  • Alias System: Named entries
  • Tomcat Support: HTTPS configuration
  • Multiple Entries: One keystore, many keys

Common Use Cases

Java Servers

Tomcat, Jetty, WildFly HTTPS

Spring Boot

Application SSL config

Android

APK signing (legacy)

Java Crypto

Encryption key storage

Advantages

  • Native Java integration (keytool)
  • Tomcat/Jetty direct support
  • Stores multiple keys (aliases)
  • Password-protected security
  • Trusted CA storage
  • Well-documented Java ecosystem
  • Spring Boot configuration support

Disadvantages

  • Deprecated since Java 9 (PKCS12 preferred)
  • Java-only (not cross-platform)
  • Proprietary binary format
  • Weak encryption (legacy algorithms)
  • Requires conversion for non-Java tools
  • Cannot be read by OpenSSL directly

Technical Information

Format Specifications

Specification Details
File Extension .jks
MIME Type application/x-java-keystore
Format Proprietary binary
Developer Oracle/Sun Microsystems
Tool Keytool (Java JDK)
Status Deprecated (Java 9+, use PKCS12)

Common Tools

  • Creation: keytool (Java JDK), Portecle (GUI)
  • Management: keytool -list, -genkeypair, -importcert
  • Conversion: keytool JKS → PKCS12, OpenSSL
  • Servers: Tomcat, Jetty, WildFly, Spring Boot