A Java code signing certificate is a digital certificate that allows developers to sign Java applications and applets cryptographically. Signing Java code provides several benefits, including verifying the identity of the code publisher, ensuring code integrity, and improving user security.

Key Takeaways

Java code signing certificates are used to sign Java applications and applets digitally.
Signing Java code verifies the identity of the publisher and ensures the code has not been tampered with.
Signed code allows users to run Java apps with elevated permissions, improving security.
Certificate authorities like Sectigo, DigiCert, etc, issue all publicly trusted certificates.
Self-signed certificates can be used for testing purposes but are not publicly trusted.
Code signing certificates confirm the authenticity and integrity of software for end users.

What Does Java Code Signing Mean

Java code signing provides a way for developers to sign their Java code using a certificate issued by a trusted certificate authority (CA). This cryptographically verifies the integrity and authenticity of the code. When users run signed Java code, it helps assure them that the code is legitimate and has not been tampered with since it was signed.

Code signing certificates are one type of digital certificate, similar to the SSL certificates used to secure websites. With code signing, the private key is used to digitally “sign” the compiled Java code, and the public key is bundled with the code so users can verify the signature.

There are several reasons why Java developers should sign their code:

Identity verification: Signing proves the publisher’s identity and assures users that the software is from a legitimate source.
Integrity: Any changes made to the signed code will invalidate the signature, proving its integrity.
Elevated permissions: Signed Java applets can request elevated permissions outside the sandbox, improving functionality.
Reputation: Signing code demonstrates the developer stands behind their software and has taken steps to prove its authenticity.

Also Read: How to Use YubiHSM For Code Signing Requests

How Does Java Code Signing Work?

Java code signing utilizes public key cryptography to validate the authenticity and integrity of Java code. Here is an overview of how the code signing process works:

Obtaining a Code Signing Certificate

The first step is to obtain a code signing certificate from a trusted certificate authority like DigiCert, Comodo, Sectigo etc.
The certificate contains the developer’s identity and their public key.
The certificate links the developer to their public key and verifies their identity.

Signing the Code

The developer compiles their Java source code into .class bytecode files.
Using their private key, the developer generates a digital signature for each .class file.
The signature is a hash value encrypted with the developer’s private key.
This signature gets embedded into the files along with the public key from the code signing certificate.

Verifying the Signature

When a user runs the signed Java code, the runtime environment first validates the certificate.
It then decrypts the signature using the public key to verify it matches the hash of the code.
If the signature verification fails, the code will not run, protecting users from tampered code.
Valid signatures prove the code’s authenticity and integrity.

This process allows users to verify that the code they are running is legitimate and unmodified since it was signed. The certificate binds the code to the developer’s identity.

Types of Java Code Signing Certificates

There are a few different types of code signing certificates that can be used for signing Java applications and applets:

Publicly Trusted Certificates

These certificates are issued by trusted CAs like DigiCert, Comodo, Symantec, and GoDaddy.
They validate the developer’s identity through extensive verification steps.
Public CAs provide the highest level of trust for users.
Java runtime environments include root certificates from major public CAs.
This allows them to verify signatures from these certificates automatically.

Self-Signed Certificates

Developers can also generate their self-signed certificates.
This allows for code signing during development and testing.
However, self-signed certificates will generate security warnings when run by users.
They should not be used to release production software since they are not publicly trusted.

Organizational CA

Large enterprises often deploy their private certificate authority.
This allows them to issue code-signing certificates for in-house software.
The root CA certificate must be manually added to trust stores on user machines.
This allows the organization’s certificates to be trusted.

Root vs. Intermediate Certificates

Certificate authorities issue two types of signing certificates:

Root certificates: These certificates represent the root CA and form the foundation of trust. The root keys are kept highly secure.
Intermediate certificates: CAs issue intermediate certificates that chain up to the root for additional security. These are used for code signing.

The intermediate certificate identifies the developer while chaining up to the root CA that browsers and Java trust.

What are the Benefits of Java Code Signing

There are several important benefits provided by signing Java applications and applets:

Verifying Publisher Identity

Code signing certificates validate the publisher’s identity through the issuing CA. This allows users to know who published the code and prevents impersonation.

Ensuring Code Integrity

The digital signature protects against modifying the code. Any changes will invalidate the signature, proving that the code has not been tampered with since signing.

Improved User Security

Signed Java applets can request elevated permissions outside the normal sandbox environment. This improves functionality while code signing protects users.

Reputation Building

Signing code instills additional trust and confidence in users and demonstrates the developer’s commitment to security and authenticity.

Simpler Software Management

IT departments can easily set policies around running signed Java code to improve security across an organization. Signing facilitates centralized control.

Interoperability

Signing code improves interoperability and ensures Java applications and applets will function as intended across platforms and devices.

By signing their Java code, developers can gain substantial trust and usability improvements for end users. The benefits make code signing a best practice for Java developers.

4 Easy Steps to Validate Signatures on Java Code

When a user runs signed Java code, the runtime environment performs signature validation automatically. Here is how it verifies the code was signed properly:

1. CA Certificate Verification

First, the CA certificate bundled with the code is checked against the Java runtime’s trusted certificate authority list. This confirms a trusted CA issued it.

2. Certificate Path Validation

Next, the full certificate chain is built and validated. This verifies the signing certificate chains up to a trusted root CA certificate.

3. Signature Decryption

The code’s digital signature is decrypted using the public key in the code signing certificate, recovering the original hash value.

4. Hash Value Matching

Finally, the decrypted hash value is compared to a freshly calculated hash of the code. If they match, the signature and code are validated.

If any step fails, the Java code will abort with a security exception and not run. The user is protected from potentially malicious unsigned or modified code.

Code Signing for Jar Files

JAR (Java ARchive) files are collections of Java class files and resources bundled into a compressed ZIP archive. JAR files are commonly used to distribute Java applications and libraries.

JAR files can also be signed using the same code-signing process. Signing the outer JAR archive protects the integrity of the entire bundle.

When a signed JAR file is used, the runtime will:

Validate the JAR file’s certificate and signature
Verify that the signatures of internal class files are valid
Confirm class files have not been tampered with

Signing the outer JAR provides security for the whole bundle. Individual class files can also be signed for added security.

How to Get a Code Signing Certificate

To start signing Java code, you will need to obtain a code signing certificate from a trusted certificate authority. Here are the steps:

Choose a Reputable CA: Major CAs like Symantec, Comodo, and DigiCert are recommended for publicly trusted code-signing certificates.
Validate Your Identity: You will need to prove your identity and ownership of the code. The CA will validate your organization and ownership.
Submit the Certificate Signing Request (CSR): Generate a CSR using the Java keytool commands or other utility. Submit this to the CA to link to your identity.
Install the Signed Certificate: Once issued, download, and install the signed certificate to use for code signing. You will use the private key to sign the code.

Self-Signing Java Code

For testing purposes, developers can also use self-signed certificates to sign Java code during development. This involves:

Generating your certificate and private key with the key tool
Signing your code JARs with your certificate
Importing the self-signed certificate into Java’s trust store

However, self-signed certificates should not be used for release software since users will see security warnings. They do not provide public trust.

Best Tips for Successfully Utilizing Java Code Signing

Here are some tips for successfully leveraging Java code signing:

Obtain certificates from a reputable, trusted CA like DigiCert or Comodo.
Use separate test and production certificates. Only sign the release code with the production certificate.
Properly secure and back up your private key for signing code.
For improved security, timestamp your signature so it cannot be cloned.
Educate users on enabling Java and always running signed code.
Set up anti-virus software, firewalls, and intrusion detection systems around code signing systems.
Re-sign the code with a new certificate before the old one expires to avoid failures.

Java Code Signing Certificate Use Cases

Java code signing provides value in several common scenarios:

Application Software Developers

Signing Java applications allows developers to prove legitimacy and gain elevated trust with end users. It is also required for granting permissions outside the sandbox.

Independent Software Vendors (ISVs)

ISVs should sign distributed Java software to demonstrate authenticity to customers and simplify enterprise administration of their applications.

Java Applet Developers

Signing applets is critical to enable permissions for applets to access local system resources and APIs for full functionality.

Enterprise Development

Businesses can sign in-house Java applications, applets, and JAR libraries to enable stronger security policies around running internal code.

Java SDK/Runtime Developers

Organizations that develop Java SDKs or alternation runtimes should sign their code distributions, so users trust the platform.

Final Thoughts

Java code signing is crucial for developers to establish trust and enable elevated permissions for Java applications and applets. It leverages public key cryptography to validate identity and integrity. Developers should obtain a trusted certificate and sign compiled JARs and class files with the private key. The Java runtime can automatically verify the signed code during launch. Following security best practices helps ensure the reliable delivery of authentic signed Java code. Signing proves legitimacy and protects users. Using trusted certificates is key to building reputation and confidence through verifiable Java code signing.

Frequently Asked Questions on Java Code Signing

Here are answers to some common questions users have about Java code signing certificates:

What are the different types of code-signing certificates?

The main types are publicly trusted certificates from CAs like DigiCert and Comodo, private organizational CAs, and self-signed certificates for internal development testing.

What information do I need to get a code signing certificate?

You will need to provide your organization’s legal identity, development identity, and ownership documentation for validation by the CA.

Can I use the same certificate for timestamping and signing code?

The best practice is to use separate certificates: one for timestamping and one for signing code: to provide separation between the functions.

Does a Java code signing certificate expire?

Yes, typically, they are valid for 1-3 years. You must renew code signing certificate before expiration, or your signed code will stop working.

What is an intermediate certificate?

A CA issues intermediate certificates to the code signer for actually signing the code. The intermediate chains up to the trusted root CA.

How much does a code signing certificate cost?

Typically, it is $80-$250 per year, depending on the validation level, trust level, and other features like timestamping.

Can I sign Java code without a certificate?

Self-signed certificates can be used for development testing but are not publicly trusted by end users running signed code.

What are the keystore file name extensions?

Java typically uses .keystore for the keystore file and .jks for the file extension. Other formats like .p12 or .pfx can also store keys.

How is the private key secured?

The private key for code signing should be carefully protected through permissions, passwords, HSMs, auditing, and other security controls.

What is a Certificate Revocation List (CRL)?

Certificate Revocation List (CRL) revoked certificates no longer trusted. Java checks the CRL to ensure the code cert is not revoked before validating signatures.

Priya Mervana

Verified Web Security Experts

Priya Mervana is working at SSLInsights.com as a web security expert with over 10 years of experience writing about encryption, SSL certificates, and online privacy. She aims to make complex security topics easily understandable for everyday internet users.

Java Code Signing Certificate: A Complete Guide For Beginners

Java Code Signing Certificate Guide