'Wrong key usage' or 'PKIX path validation failed'

Question

Problem:

When the browser (on Windows) tries to load the IntegralFTP applet, a message-box pops up with the following error:

The publisher cannot be verified by a trusted source. Code will be treated as unsigned.

Name: 0

ValidatorException: PKIX path validation failed: java.security.cert.CertPathValidatorException: java.security.InvalidKeyException: Wrong key usage

After this IntegralFTP fails to initialize and is unusable. If you click the Details button you get:

sun.security.validator.ValidatorException: PKIX path validation failed: java.security.cert.CertPathValidatorException: java.security.InvalidKeyException: Wrong key usage
at sun.security.validator.PKIXValidator.doValidate(Unknown Source)
at sun.security.validator.PKIXValidator.engineValidate(Unknown Source)
at sun.security.validator.Validator.validate(Unknown Source)
at sun.security.validator.Validator.validate(Unknown Source)
at sun.security.validator.Validator.validate(Unknown Source)
at com.sun.deploy.security.TrustDecider.validateChain(Unknown Source)
at com.sun.deploy.security.TrustDecider.isAllPermissionGranted(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.isTrustedByTrustDecider(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.getTrustedCodeSources(Unknown Source)
at com.sun.deploy.security.CPCallbackHandler$ParentCallback.strategy(Unknown Source)
at com.sun.deploy.security.CPCallbackHandler$ParentCallback.openClassPathElement(Unknown Source)
at com.sun.deploy.security.DeployURLClassPath$JarLoader.getJarFile(Unknown Source)
at com.sun.deploy.security.DeployURLClassPath$JarLoader.access$1000(Unknown Source)
at com.sun.deploy.security.DeployURLClassPath$JarLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.deploy.security.DeployURLClassPath$JarLoader.ensureOpen(Unknown Source)
at com.sun.deploy.security.DeployURLClassPath$JarLoader.<init>(Unknown Source)
at com.sun.deploy.security.DeployURLClassPath$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.deploy.security.DeployURLClassPath.getLoader(Unknown Source)
at com.sun.deploy.security.DeployURLClassPath.getLoader(Unknown Source)
at com.sun.deploy.security.DeployURLClassPath.getResource(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader$2.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.plugin2.applet.Plugin2ClassLoader.findClassHelper(Unknown Source)
at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Unknown Source)
at sun.plugin2.applet.Plugin2Manager.initAppletAdapter(Unknown Source)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.security.cert.CertPathValidatorException: java.security.InvalidKeyException: Wrong key usage
at sun.security.provider.certpath.PKIXMasterCertPathValidator.validate(Unknown Source)
at sun.security.provider.certpath.PKIXCertPathValidator.doValidate(Unknown Source)
at sun.security.provider.certpath.PKIXCertPathValidator.engineValidate(Unknown Source)
at java.security.cert.CertPathValidator.validate(Unknown Source)
... 36 more
Caused by: java.security.InvalidKeyException: Wrong key usage
at java.security.Signature.initVerify(Unknown Source)
at sun.security.provider.certpath.OCSPResponse.verifyResponse(Unknown Source)
at sun.security.provider.certpath.OCSPResponse.<init>(Unknown Source)
at sun.security.provider.certpath.OCSP.check(Unknown Source)
at sun.security.provider.certpath.OCSPChecker.check(Unknown Source)
... 40 more

Cause:

This problem is caused by a bug in Java 7 update 6 and 7. Oracle is aware of the bug and is working on it (see here).

Workaround:

Until Oracle fixes it, the workaround is to disable 'online certificate verification'. To do this:

1. open the Windows Control Panel
2. select 'Java (32-bit)' or 'Java (64-bit)'
3. select the 'Advanced' tab
4. scroll down to the Security -> General section
5. untick 'Enable online certificate validation'

Scope:

We suspect that the problem may only occur on machines that have new installations of Java 7u6 or 7u7, as opposed to installations that were upgraded from previous versions. The reason for this is that from 7u6 'Enable online certification validation' is ticked by default.