How to retrieve/compute an X509 certificate's thumbprint in Java?

certificate, java

Solution

The SHA-1 hash of the DER encoding of the certificate is what .NET is getting with X509Certificate2.Thumbprint.

As noted on the remarks on MSDN:

The thumbprint is dynamically generated using the SHA1 algorithm and does not physically exist in the certificate. Since the thumbprint is a unique value for the certificate, it is commonly used to find a particular certificate in a certificate store.

Java's standard library doesn't provide the thumbprint directly, but you can get it like this:

DatatypeConverter.printHexBinary(
        MessageDigest.getInstance("SHA-1").digest(
                cert.getEncoded())).toLowerCase();

Here's a full worked example using a conveniently accessible PEM file:

Create stackoverflow.crt.pem:

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

Create X509.java:

import javax.xml.bind.DatatypeConverter;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateEncodingException;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;

public final class X509 {
    public static void main(String[] args)
            throws FileNotFoundException, CertificateException, NoSuchAlgorithmException {
        FileInputStream is = new FileInputStream(args[0]);
        CertificateFactory certificateFactory = CertificateFactory.getInstance("X.509");
        X509Certificate cert = (X509Certificate) certificateFactory.generateCertificate(is);
        String thumbprint = getThumbprint(cert);
        System.out.println(thumbprint);
    }

    private static String getThumbprint(X509Certificate cert)
            throws NoSuchAlgorithmException, CertificateEncodingException {
        MessageDigest md = MessageDigest.getInstance("SHA-1");
        byte[] der = cert.getEncoded();
        md.update(der);
        byte[] digest = md.digest();
        String digestHex = DatatypeConverter.printHexBinary(digest);
        return digestHex.toLowerCase();
    }
}

Compile the program with Java 8:

javac X509.java

Or Java 9 - due to modular JDK/JPMS - DataTypeConverter is not in java.base, but java.xml.bind, so you need to explicitly depend on it during your build:

javac --add-modules java.xml.bind X509.java

Otherwise, on Java 9, you get this when you try to build it:

X509.java:3: error: package javax.xml.bind is not visible
        import javax.xml.bind.DatatypeConverter;
        ^
        (package javax.xml.bind is declared in module java.xml.bind, which is not in the module graph)
        1 error

Run it with Java 8:

java X509 stackoverflow.crt.pem

In Java 9 - due to modular JDK/JPMS - DataTypeConverter is not in java.base, but java.xml.bind, so you need to explicitly depend on it when running your program:

java --add-modules java.xml.bind X509 stackoverflow.crt.pem

Otherwise, on Java 9, you get this when you try to run it:

Exception in thread "main" java.lang.NoClassDefFoundError: javax/xml/bind/DatatypeConverter
    at X509.getThumbPrint(X509.java:29)
    at X509.main(X509.java:19)
    Caused by: java.lang.ClassNotFoundException: javax.xml.bind.DatatypeConverter
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:582)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:185)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:496)
    ... 2 more

Get the expected output:

47adb03649a2eb18f63ffa29790818349a99cab7

Problem

I have a java client that is calling a web service operation which takes a certificate "thumbprint" as a parameter. I believe the thumbprint is some kind of SHA1 hash, in hexadecimal string format, of the cert's public key, but I'm not sure. The .NET framework seems to include a simple way to get this value (X509Certificate2.Thumbprint property). Viewing a .cer file's properties in Windows also displays the thumbprint, which looks like: ``` a6 9c fd b0 58 0d a4 ee ae 9a 47 75 24 c3 0b 9f 5d b6 1c 77 ``` My question is therefore: Does anybody know how to retrieve or compute this thumbprint string within Java, if I have an instance of a java.security.cert.X509Certificate?

Original source