itextpdf.jar is a component in iText 5 Java library to provide core functionalities. iText Java library allows you to generate and manage PDF documents.

The Source Code files are provided at iText GitHub site.

You can compile it to generate your JAR file, using pom.xml as the build configuration file.

The source code of itextpdf-5.5.14.jar is provided below:

⏎ com/itextpdf/text/pdf/PdfPublicKeySecurityHandler.java

/*
 *
 * This file is part of the iText (R) project.
    Copyright (c) 1998-2020 iText Group NV
 * Authors: Bruno Lowagie, Paulo Soares, et al.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License version 3
 * as published by the Free Software Foundation with the addition of the
 * following permission added to Section 15 as permitted in Section 7(a):
 * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
 * ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
 * OF THIRD PARTY RIGHTS
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Affero General Public License for more details.
 * You should have received a copy of the GNU Affero General Public License
 * along with this program; if not, see http://www.gnu.org/licenses or write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA, 02110-1301 USA, or download the license from the following URL:
 * http://itextpdf.com/terms-of-use/
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General Public License.
 *
 * In accordance with Section 7(b) of the GNU Affero General Public License,
 * a covered work must retain the producer line in every PDF that is created
 * or manipulated using iText.
 *
 * You can be released from the requirements of the license by purchasing
 * a commercial license. Buying such a license is mandatory as soon as you
 * develop commercial activities involving the iText software without
 * disclosing the source code of your own applications.
 * These activities include: offering paid services to customers as an ASP,
 * serving PDFs on the fly in a web application, shipping iText with a closed
 * source product.
 *
 * For more information, please contact iText Software Corp. at this
 * address: sales@itextpdf.com
 */

/**
 *     The below 2 methods are from pdfbox.
 *
 *     private ASN1Primitive createDERForRecipient(byte[] in, X509Certificate cert) ;
 *     private KeyTransRecipientInfo computeRecipientInfo(X509Certificate x509certificate, byte[] abyte0);
 *
 *     2006-11-22 Aiken Sam.
 */

/**
 * Copyright (c) 2003-2006, www.pdfbox.org
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. Neither the name of pdfbox; nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * http://www.pdfbox.org
 *
 */

package com.itextpdf.text.pdf;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.security.AlgorithmParameterGenerator;
import java.security.AlgorithmParameters;
import java.security.GeneralSecurityException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.cert.Certificate;
import java.security.cert.X509Certificate;
import java.util.ArrayList;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;

import org.bouncycastle.asn1.ASN1InputStream;
import org.bouncycastle.asn1.ASN1Primitive;
import org.bouncycastle.asn1.ASN1ObjectIdentifier;
import org.bouncycastle.asn1.ASN1Set;
import org.bouncycastle.asn1.DEROctetString;
import org.bouncycastle.asn1.DEROutputStream;
import org.bouncycastle.asn1.DERSet;
import org.bouncycastle.asn1.cms.ContentInfo;
import org.bouncycastle.asn1.cms.EncryptedContentInfo;
import org.bouncycastle.asn1.cms.EnvelopedData;
import org.bouncycastle.asn1.cms.IssuerAndSerialNumber;
import org.bouncycastle.asn1.cms.KeyTransRecipientInfo;
import org.bouncycastle.asn1.cms.RecipientIdentifier;
import org.bouncycastle.asn1.cms.RecipientInfo;
import org.bouncycastle.asn1.pkcs.PKCSObjectIdentifiers;
import org.bouncycastle.asn1.x509.AlgorithmIdentifier;
import org.bouncycastle.asn1.x509.TBSCertificateStructure;

/**
 * @author Aiken Sam (aikensam@ieee.org)
 */
public class PdfPublicKeySecurityHandler {

    static final int SEED_LENGTH = 20;

    private ArrayList<PdfPublicKeyRecipient> recipients = null;

    private byte[] seed = new byte[SEED_LENGTH];

    public PdfPublicKeySecurityHandler() {
        KeyGenerator key;
        try {
            key = KeyGenerator.getInstance("AES");
            key.init(192, new SecureRandom());
            SecretKey sk = key.generateKey();
            System.arraycopy(sk.getEncoded(), 0, seed, 0, SEED_LENGTH); // create the 20 bytes seed
        } catch (NoSuchAlgorithmException e) {
            seed = SecureRandom.getSeed(SEED_LENGTH);
        }

        recipients = new ArrayList<PdfPublicKeyRecipient>();
    }

    public void addRecipient(PdfPublicKeyRecipient recipient) {
        recipients.add(recipient);
    }

    protected byte[] getSeed() {
        return seed.clone();
    }
    /*
    public PdfPublicKeyRecipient[] getRecipients() {
        recipients.toArray();
        return (PdfPublicKeyRecipient[])recipients.toArray();
    }*/

    public int getRecipientsSize() {
        return recipients.size();
    }

    public byte[] getEncodedRecipient(int index) throws IOException, GeneralSecurityException {
        //Certificate certificate = recipient.getX509();
        PdfPublicKeyRecipient recipient = recipients.get(index);
        byte[] cms = recipient.getCms();

        if (cms != null) return cms;

        Certificate certificate  = recipient.getCertificate();
        int permission =  recipient.getPermission();//PdfWriter.AllowCopy | PdfWriter.AllowPrinting | PdfWriter.AllowScreenReaders | PdfWriter.AllowAssembly;
        int revision = 3;

        permission |= revision==3 ? 0xfffff0c0 : 0xffffffc0;
        permission &= 0xfffffffc;
        permission += 1;

        byte[] pkcs7input = new byte[24];

        byte one = (byte)permission;
        byte two = (byte)(permission >> 8);
        byte three = (byte)(permission >> 16);
        byte four = (byte)(permission >> 24);

        System.arraycopy(seed, 0, pkcs7input, 0, 20); // put this seed in the pkcs7 input

        pkcs7input[20] = four;
        pkcs7input[21] = three;
        pkcs7input[22] = two;
        pkcs7input[23] = one;

        ASN1Primitive obj = createDERForRecipient(pkcs7input, (X509Certificate)certificate);

        ByteArrayOutputStream baos = new ByteArrayOutputStream();

        DEROutputStream k = new DEROutputStream(baos);

        k.writeObject(obj);

        cms = baos.toByteArray();

        recipient.setCms(cms);

        return cms;
    }

    public PdfArray getEncodedRecipients() throws IOException,
                                         GeneralSecurityException {
        PdfArray EncodedRecipients = new PdfArray();
        byte[] cms = null;
        for (int i=0; i<recipients.size(); i++)
        try {
            cms = getEncodedRecipient(i);
            EncodedRecipients.add(new PdfLiteral(StringUtils.escapeString(cms)));
        } catch (GeneralSecurityException e) {
            EncodedRecipients = null;
        } catch (IOException e) {
            EncodedRecipients = null;
        }

        return EncodedRecipients;
    }

    private ASN1Primitive createDERForRecipient(byte[] in, X509Certificate cert)
        throws IOException,
               GeneralSecurityException
    {

        String s = "1.2.840.113549.3.2";

        AlgorithmParameterGenerator algorithmparametergenerator = AlgorithmParameterGenerator.getInstance(s);
        AlgorithmParameters algorithmparameters = algorithmparametergenerator.generateParameters();
        ByteArrayInputStream bytearrayinputstream = new ByteArrayInputStream(algorithmparameters.getEncoded("ASN.1"));
        ASN1InputStream asn1inputstream = new ASN1InputStream(bytearrayinputstream);
        ASN1Primitive derobject = asn1inputstream.readObject();
        KeyGenerator keygenerator = KeyGenerator.getInstance(s);
        keygenerator.init(128);
        SecretKey secretkey = keygenerator.generateKey();
        Cipher cipher = Cipher.getInstance(s);
        cipher.init(1, secretkey, algorithmparameters);
        byte[] abyte1 = cipher.doFinal(in);
        DEROctetString deroctetstring = new DEROctetString(abyte1);
        KeyTransRecipientInfo keytransrecipientinfo = computeRecipientInfo(cert, secretkey.getEncoded());
        DERSet derset = new DERSet(new RecipientInfo(keytransrecipientinfo));
        AlgorithmIdentifier algorithmidentifier = new AlgorithmIdentifier(new ASN1ObjectIdentifier(s), derobject);
        EncryptedContentInfo encryptedcontentinfo =
            new EncryptedContentInfo(PKCSObjectIdentifiers.data, algorithmidentifier, deroctetstring);
        ASN1Set set = null;
        EnvelopedData env = new EnvelopedData(null, derset, encryptedcontentinfo, set);
        ContentInfo contentinfo =
            new ContentInfo(PKCSObjectIdentifiers.envelopedData, env);
        return contentinfo.toASN1Primitive();
    }

    private KeyTransRecipientInfo computeRecipientInfo(X509Certificate x509certificate, byte[] abyte0)
        throws GeneralSecurityException, IOException
    {
        ASN1InputStream asn1inputstream =
            new ASN1InputStream(new ByteArrayInputStream(x509certificate.getTBSCertificate()));
        TBSCertificateStructure tbscertificatestructure =
            TBSCertificateStructure.getInstance(asn1inputstream.readObject());
        AlgorithmIdentifier algorithmidentifier = tbscertificatestructure.getSubjectPublicKeyInfo().getAlgorithm();
        IssuerAndSerialNumber issuerandserialnumber =
            new IssuerAndSerialNumber(
                tbscertificatestructure.getIssuer(),
                tbscertificatestructure.getSerialNumber().getValue());
        Cipher cipher = Cipher.getInstance(algorithmidentifier.getAlgorithm().getId());
        try{
        cipher.init(1, x509certificate);
        }catch(InvalidKeyException e){
        	cipher.init(1,x509certificate.getPublicKey());
        }
        DEROctetString deroctetstring = new DEROctetString(cipher.doFinal(abyte0));
        RecipientIdentifier recipId = new RecipientIdentifier(issuerandserialnumber);
        return new KeyTransRecipientInfo( recipId, algorithmidentifier, deroctetstring);
    }
}

⏎ com/itextpdf/text/pdf/PdfPublicKeySecurityHandler.java

Or download all of them as a single archive file:

File name: itextpdf-5.5.14-fyi.zip
File size: 2163839 bytes
Release date: 2009-10-09
Download 

⇒ iText-2.1.6.jar - iText, a JAVA-PDF library

⇐ iText layout.jar Source Code

⇑ Download and Install iText Java Library

⇑⇑ iText for PDF Generation