http://www.bouncycastle.org/java.html: The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar contains APIs for JDK 1.5 to JDK 1.8. The APIs can be used in conjunction with a JCE/JCA provider such as the one provided with the Bouncy Castle Cryptography APIs.
  • The Legion of the Bouncy Castle Inc. 
package org.bouncycastle.cert;

import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo;
import org.bouncycastle.operator.ContentVerifierProvider;
import org.bouncycastle.operator.OperatorCreationException;

public interface X509ContentVerifierProviderBuilder
{
    ContentVerifierProvider build(SubjectPublicKeyInfo validatingKeyInfo)
        throws OperatorCreationException;

    ContentVerifierProvider build(X509CertificateHolder validatingKeyInfo)
        throws OperatorCreationException;
}