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.mime.smime;

import java.io.IOException;
import java.io.InputStream;

import org.bouncycastle.mime.BasicMimeParser;
import org.bouncycastle.mime.Headers;
import org.bouncycastle.mime.MimeParser;
import org.bouncycastle.mime.MimeParserProvider;
import org.bouncycastle.operator.DigestCalculatorProvider;

public class SMimeParserProvider
    implements MimeParserProvider
{
    private final String defaultContentTransferEncoding;
    private final DigestCalculatorProvider digestCalculatorProvider;

    public SMimeParserProvider(String defaultContentTransferEncoding, DigestCalculatorProvider digestCalculatorProvider)
    {
        this.defaultContentTransferEncoding = defaultContentTransferEncoding;
        this.digestCalculatorProvider = digestCalculatorProvider;
    }

    public MimeParser createParser(InputStream source)
        throws IOException
    {
        return new BasicMimeParser(new SMimeParserContext(defaultContentTransferEncoding, digestCalculatorProvider), source);
    }

    public MimeParser createParser(Headers headers, InputStream source)
        throws IOException
    {
        return new BasicMimeParser(new SMimeParserContext(defaultContentTransferEncoding, digestCalculatorProvider), headers, source);
    }
}