http://www.bouncycastle.org/java.html: The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.7. 
package org.bouncycastle.asn1.cms;

import org.bouncycastle.asn1.ASN1SequenceParser;
import org.bouncycastle.asn1.ASN1SetParser;
import org.bouncycastle.asn1.ASN1TaggedObjectParser;
import org.bouncycastle.asn1.DEREncodable;
import org.bouncycastle.asn1.DERInteger;
import org.bouncycastle.asn1.DERTags;

import java.io.IOException;


EnvelopedData ::= SEQUENCE {
    version CMSVersion,
    originatorInfo [0] IMPLICIT OriginatorInfo OPTIONAL,
    recipientInfos RecipientInfos,
    encryptedContentInfo EncryptedContentInfo,
    unprotectedAttrs [1] IMPLICIT UnprotectedAttributes OPTIONAL 
}



/** 
 * <pre>
 * EnvelopedData ::= SEQUENCE {
 *     version CMSVersion,
 *     originatorInfo [0] IMPLICIT OriginatorInfo OPTIONAL,
 *     recipientInfos RecipientInfos,
 *     encryptedContentInfo EncryptedContentInfo,
 *     unprotectedAttrs [1] IMPLICIT UnprotectedAttributes OPTIONAL 
 * }
 * </pre>
 */
public class EnvelopedDataParser
{
    private ASN1SequenceParser _seq;
    private DERInteger         _version;
    private DEREncodable       _nextObject;
    private boolean            _originatorInfoCalled;
    
    public EnvelopedDataParser(
        ASN1SequenceParser seq)
        throws IOException
    {
        this._seq = seq;
        this._version = (DERInteger)seq.readObject();
    }

    public DERInteger getVersion()
    {
        return _version;
    }

    public OriginatorInfo getOriginatorInfo() 
        throws IOException
    {
        _originatorInfoCalled = true; 
        
        if (_nextObject == null)
        {
            _nextObject = _seq.readObject();
        }
        
        if (_nextObject instanceof ASN1TaggedObjectParser && ((ASN1TaggedObjectParser)_nextObject).getTagNo() == 0)
        {
            ASN1SequenceParser originatorInfo = (ASN1SequenceParser) ((ASN1TaggedObjectParser)_nextObject).getObjectParser(DERTags.SEQUENCE, false);
            _nextObject = null;
            return OriginatorInfo.getInstance(originatorInfo.getDERObject());
        }
        
        return null;
    }
    
    public ASN1SetParser getRecipientInfos()
        throws IOException
    {
        if (!_originatorInfoCalled)
        {
            getOriginatorInfo();
        }
        
        if (_nextObject == null)
        {
            _nextObject = _seq.readObject();
        }
        
        ASN1SetParser recipientInfos = (ASN1SetParser)_nextObject;
        _nextObject = null;
        return recipientInfos;
    }

    public EncryptedContentInfoParser getEncryptedContentInfo() 
        throws IOException
    {
        if (_nextObject == null)
        {
            _nextObject = _seq.readObject();
        }
        
        
        if (_nextObject != null)
        {
            ASN1SequenceParser o = (ASN1SequenceParser) _nextObject;
            _nextObject = null;
            return new EncryptedContentInfoParser(o);
        }
        
        return null;
    }

    public ASN1SetParser getUnprotectedAttrs()
        throws IOException
    {
        if (_nextObject == null)
        {
            _nextObject = _seq.readObject();
        }
        
        
        if (_nextObject != null)
        {
            DEREncodable o = _nextObject;
            _nextObject = null;
            return (ASN1SetParser)((ASN1TaggedObjectParser)o).getObjectParser(DERTags.SET, false);
        }
        
        return null;
    }
}