From 6025b6016517c6d898d8957d1d7e03ba71431912 Mon Sep 17 00:00:00 2001
From: tknall <tknall@7b5415b0-85f9-ee4d-85bd-d5d0c3b42d1c>
Date: Fri, 1 Dec 2006 12:20:24 +0000
Subject: Initial import of release 2.2.

git-svn-id: https://joinup.ec.europa.eu/svn/pdf-as/trunk@4 7b5415b0-85f9-ee4d-85bd-d5d0c3b42d1c
---
 src/main/java/org/pdfbox/encryption/ARCFour.java   | 182 +++++++
 .../org/pdfbox/encryption/DocumentEncryption.java  | 427 +++++++++++++++
 .../java/org/pdfbox/encryption/PDFEncryption.java  | 599 +++++++++++++++++++++
 src/main/java/org/pdfbox/encryption/package.html   |   9 +
 4 files changed, 1217 insertions(+)
 create mode 100644 src/main/java/org/pdfbox/encryption/ARCFour.java
 create mode 100644 src/main/java/org/pdfbox/encryption/DocumentEncryption.java
 create mode 100644 src/main/java/org/pdfbox/encryption/PDFEncryption.java
 create mode 100644 src/main/java/org/pdfbox/encryption/package.html

(limited to 'src/main/java/org/pdfbox/encryption')

diff --git a/src/main/java/org/pdfbox/encryption/ARCFour.java b/src/main/java/org/pdfbox/encryption/ARCFour.java
new file mode 100644
index 0000000..6eeeb95
--- /dev/null
+++ b/src/main/java/org/pdfbox/encryption/ARCFour.java
@@ -0,0 +1,182 @@
+/**
+ * Copyright (c) 2003, 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 org.pdfbox.encryption;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+/**
+ * This class is an implementation of the alleged RC4 algorithm.
+ *
+ * @author Ben Litchfield
+ * @version $Revision: 1.7 $
+ */
+public class ARCFour
+{
+    private int[] salt;
+    private int b;
+    private int c;
+
+    /**
+     * Constructor.
+     *
+     */
+    public ARCFour()
+    {
+        salt = new int[256];
+    }
+
+    /**
+     * This will reset the key to be used.
+     *
+     * @param key The RC4 key used during encryption.
+    */
+    public void setKey( byte[] key )
+    {
+        b = 0;
+        c = 0;
+
+        if(key.length < 1 || key.length > 32)
+        {
+            throw new IllegalArgumentException("number of bytes must be between 1 and 32");
+        }
+        for(int i = 0; i < salt.length; i++)
+        {
+            salt[i] = i;
+        }
+
+        int keyIndex = 0;
+        int saltIndex = 0;
+        for( int i = 0; i < salt.length; i++)
+        {
+            saltIndex = (fixByte(key[keyIndex]) + salt[i] + saltIndex) % 256;
+            swap( salt, i, saltIndex );
+            keyIndex = (keyIndex + 1) % key.length;
+        }
+
+    }
+
+    /**
+     * Thie will ensure that the value for a byte >=0.
+     *
+     * @param aByte The byte to test against.
+     *
+     * @return A value >=0 and < 256
+     */
+    private static final int fixByte( byte aByte )
+    {
+        return aByte < 0 ? 256 + aByte : aByte;
+    }
+
+    /**
+     * This will swap two values in an array.
+     *
+     * @param data The array to swap from.
+     * @param firstIndex The index of the first element to swap.
+     * @param secondIndex The index of the second element to swap.
+     */
+    private static final void swap( int[] data, int firstIndex, int secondIndex )
+    {
+        int tmp = data[ firstIndex ];
+        data[ firstIndex ] = data[ secondIndex ];
+        data[ secondIndex ] = tmp;
+    }
+
+    /**
+     * This will encrypt and write the next byte.
+     *
+     * @param aByte The byte to encrypt.
+     * @param output The stream to write to.
+     *
+     * @throws IOException If there is an error writing to the output stream.
+     */
+    public void write( byte aByte, OutputStream output ) throws IOException
+    {
+        b = (b + 1) % 256;
+        c = (salt[b] + c) % 256;
+        swap( salt, b, c );
+        int saltIndex = (salt[b] + salt[c]) % 256;
+        output.write(aByte ^ (byte)salt[saltIndex]);
+    }
+
+    /**
+     * This will encrypt and write the data.
+     *
+     * @param data The data to encrypt.
+     * @param output The stream to write to.
+     *
+     * @throws IOException If there is an error writing to the output stream.
+     */
+    public void write( byte[] data, OutputStream output ) throws IOException
+    {
+        for( int i = 0; i < data.length; i++ )
+        {
+            write( data[i], output );
+        }
+    }
+
+    /**
+     * This will encrypt and write the data.
+     *
+     * @param data The data to encrypt.
+     * @param output The stream to write to.
+     *
+     * @throws IOException If there is an error writing to the output stream.
+     */
+    public void write( InputStream data, OutputStream output ) throws IOException
+    {
+        byte[] buffer = new byte[1024];
+        int amountRead = 0;
+        while( (amountRead = data.read( buffer )) != -1 )
+        {
+            write( buffer, 0, amountRead, output );
+        }
+    }
+
+    /**
+     * This will encrypt and write the data.
+     *
+     * @param data The data to encrypt.
+     * @param offset The offset into the array to start reading data from.
+     * @param len The number of bytes to attempt to read.
+     * @param output The stream to write to.
+     *
+     * @throws IOException If there is an error writing to the output stream.
+     */
+    public void write( byte[] data, int offset, int len, OutputStream output) throws IOException
+    {
+        for( int i = offset; i < offset + len; i++ )
+        {
+            write( data[i], output );
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/org/pdfbox/encryption/DocumentEncryption.java b/src/main/java/org/pdfbox/encryption/DocumentEncryption.java
new file mode 100644
index 0000000..9ae6936
--- /dev/null
+++ b/src/main/java/org/pdfbox/encryption/DocumentEncryption.java
@@ -0,0 +1,427 @@
+/**
+ * Copyright (c) 2003-2004, 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 org.pdfbox.encryption;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+import java.io.IOException;
+
+import java.math.BigInteger;
+
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Set;
+
+import org.pdfbox.exceptions.CryptographyException;
+import org.pdfbox.exceptions.InvalidPasswordException;
+
+import org.pdfbox.cos.COSArray;
+import org.pdfbox.cos.COSBase;
+import org.pdfbox.cos.COSDictionary;
+import org.pdfbox.cos.COSDocument;
+import org.pdfbox.cos.COSName;
+import org.pdfbox.cos.COSObject;
+import org.pdfbox.cos.COSStream;
+import org.pdfbox.cos.COSString;
+
+import org.pdfbox.pdmodel.PDDocument;
+
+import org.pdfbox.pdmodel.encryption.PDStandardEncryption;
+
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+/**
+ * This class will deal with encrypting/decrypting a document.
+ *
+ * @author Ben Litchfield (ben@benlitchfield.com)
+ * @version $Revision: 1.10 $
+ */
+public class DocumentEncryption
+{
+    private PDDocument pdDocument = null;
+    private COSDocument document = null;
+
+    private byte[] encryptionKey = null;
+    private PDFEncryption encryption = new PDFEncryption();
+
+    private Set objects = new HashSet();
+    
+    /**
+     * A set that contains potential signature dictionaries.  This is used
+     * because the Contents entry of the signature is not encrypted.
+     */
+    private Set potentialSignatures = new HashSet();
+
+    /**
+     * Constructor.
+     *
+     * @param doc The document to decrypt.
+     */
+    public DocumentEncryption( PDDocument doc )
+    {
+        pdDocument = doc;
+        document = doc.getDocument();
+    }
+
+    /**
+     * Constructor.
+     *
+     * @param doc The document to decrypt.
+     */
+    public DocumentEncryption( COSDocument doc )
+    {
+        pdDocument = new PDDocument( doc );
+        document = doc;
+    }
+
+    /**
+     * This will encrypt the given document, given the owner password and user password.
+     * The encryption method used is the standard filter.
+     *
+     * @throws CryptographyException If an error occurs during encryption.
+     * @throws IOException If there is an error accessing the data.
+     */
+    public void initForEncryption()
+        throws CryptographyException, IOException
+    {
+        String ownerPassword = pdDocument.getOwnerPasswordForEncryption();
+        String userPassword = pdDocument.getUserPasswordForEncryption();
+        if( ownerPassword == null )
+        {
+            ownerPassword = "";
+        }
+        if( userPassword == null )
+        {
+            userPassword = "";
+        }
+        PDStandardEncryption encParameters = (PDStandardEncryption)pdDocument.getEncryptionDictionary();
+        int permissionInt = encParameters.getPermissions();
+        int revision = encParameters.getRevision();
+        int length = encParameters.getLength()/8;
+        COSArray idArray = document.getDocumentID();
+
+        //check if the document has an id yet.  If it does not then
+        //generate one
+        if( idArray == null || idArray.size() < 2 )
+        {
+            idArray = new COSArray();
+            try
+            {
+                MessageDigest md = MessageDigest.getInstance( "MD5" );
+                BigInteger time = BigInteger.valueOf( System.currentTimeMillis() );
+                md.update( time.toByteArray() );
+                md.update( ownerPassword.getBytes() );
+                md.update( userPassword.getBytes() );
+                md.update( document.toString().getBytes() );
+                byte[] id = md.digest( this.toString().getBytes() );
+                COSString idString = new COSString();
+                idString.append( id );
+                idArray.add( idString );
+                idArray.add( idString );
+                document.setDocumentID( idArray );
+            }
+            catch( NoSuchAlgorithmException e )
+            {
+                throw new CryptographyException( e );
+            }
+
+        }
+        COSString id = (COSString)idArray.getObject( 0 );
+        encryption = new PDFEncryption();
+
+        byte[] o = encryption.computeOwnerPassword(
+            ownerPassword.getBytes("ISO-8859-1"),
+            userPassword.getBytes("ISO-8859-1"), revision, length);
+
+        byte[] u = encryption.computeUserPassword(
+            userPassword.getBytes("ISO-8859-1"),
+            o, permissionInt, id.getBytes(), revision, length);
+
+        encryptionKey = encryption.computeEncryptedKey(
+            userPassword.getBytes("ISO-8859-1"), o, permissionInt, id.getBytes(), revision, length);
+
+        encParameters.setOwnerKey( o );
+        encParameters.setUserKey( u );
+        
+        document.setEncryptionDictionary( encParameters.getCOSDictionary() );
+    }
+    
+    
+
+    /**
+     * This will decrypt the document.
+     *
+     * @param password The password for the document.
+     *
+     * @throws CryptographyException If there is an error decrypting the document.
+     * @throws IOException If there is an error getting the stream data.
+     * @throws InvalidPasswordException If the password is not a user or owner password.
+     */
+    public void decryptDocument( String password )
+        throws CryptographyException, IOException, InvalidPasswordException
+    {
+        if( password == null )
+        {
+            password = "";
+        }
+
+        PDStandardEncryption encParameters = (PDStandardEncryption)pdDocument.getEncryptionDictionary();
+
+
+        int permissions = encParameters.getPermissions();
+        int revision = encParameters.getRevision();
+        int length = encParameters.getLength()/8;
+
+        COSString id = (COSString)document.getDocumentID().getObject( 0 );
+        byte[] u = encParameters.getUserKey();
+        byte[] o = encParameters.getOwnerKey();
+
+        boolean isUserPassword =
+            encryption.isUserPassword( password.getBytes(), u,
+                o, permissions, id.getBytes(), revision, length );
+        boolean isOwnerPassword =
+            encryption.isOwnerPassword( password.getBytes(), u,
+                o, permissions, id.getBytes(), revision, length );
+
+        if( isUserPassword )
+        {
+            encryptionKey =
+                encryption.computeEncryptedKey(
+                    password.getBytes(), o,
+                    permissions, id.getBytes(), revision, length );
+        }
+        else if( isOwnerPassword )
+        {
+            byte[] computedUserPassword =
+                encryption.getUserPassword(
+                    password.getBytes(),
+                    o,
+                    revision,
+                    length );
+            encryptionKey =
+                encryption.computeEncryptedKey(
+                    computedUserPassword, o,
+                    permissions, id.getBytes(), revision, length );
+        }
+        else
+        {
+            throw new InvalidPasswordException( "Error: The supplied password does not match " +
+                                                "either the owner or user password in the document." );
+        }
+        
+        COSDictionary trailer = document.getTrailer();
+        COSArray fields = (COSArray)trailer.getObjectFromPath( "Root/AcroForm/Fields" );
+        
+        //We need to collect all the signature dictionaries, for some
+        //reason the 'Contents' entry of signatures is not really encrypted
+        if( fields != null )
+        {
+            for( int i=0; i<fields.size(); i++ )
+            {
+                COSDictionary field = (COSDictionary)fields.getObject( i );
+                addDictionaryAndSubDictionary( potentialSignatures, field );
+            }
+        }
+
+        List allObjects = document.getObjects();
+        Iterator objectIter = allObjects.iterator();
+        while( objectIter.hasNext() )
+        {
+            decryptObject( (COSObject)objectIter.next() );
+        }
+        document.setEncryptionDictionary( null );
+    }
+    
+    private void addDictionaryAndSubDictionary( Set set, COSDictionary dic )
+    {
+        set.add( dic );
+        COSArray kids = (COSArray)dic.getDictionaryObject( "Kids" );
+        for( int i=0; kids != null && i<kids.size(); i++ )
+        {
+            addDictionaryAndSubDictionary( set, (COSDictionary)kids.getObject( i ) );
+        }
+        COSBase value = dic.getDictionaryObject( "V" );
+        if( value instanceof COSDictionary )
+        {
+            addDictionaryAndSubDictionary( set, (COSDictionary)value );
+        }
+    }
+
+    /**
+     * This will decrypt an object in the document.
+     *
+     * @param object The object to decrypt.
+     *
+     * @throws CryptographyException If there is an error decrypting the stream.
+     * @throws IOException If there is an error getting the stream data.
+     */
+    private void decryptObject( COSObject object )
+        throws CryptographyException, IOException
+    {
+        long objNum = object.getObjectNumber().intValue();
+        long genNum = object.getGenerationNumber().intValue();
+        COSBase base = object.getObject();
+        decrypt( base, objNum, genNum );
+    }
+
+    /**
+     * This will dispatch to the correct method.
+     *
+     * @param obj The object to decrypt.
+     * @param objNum The object number.
+     * @param genNum The object generation Number.
+     *
+     * @throws CryptographyException If there is an error decrypting the stream.
+     * @throws IOException If there is an error getting the stream data.
+     */
+    private void decrypt( Object obj, long objNum, long genNum )
+        throws CryptographyException, IOException
+    {
+        if( !objects.contains( obj ) )
+        {
+            objects.add( obj );
+
+            if( obj instanceof COSString )
+            {
+                decryptString( (COSString)obj, objNum, genNum );
+            }
+            else if( obj instanceof COSStream )
+            {
+                decryptStream( (COSStream)obj, objNum, genNum );
+            }
+            else if( obj instanceof COSDictionary )
+            {
+                decryptDictionary( (COSDictionary)obj, objNum, genNum );
+            }
+            else if( obj instanceof COSArray )
+            {
+                decryptArray( (COSArray)obj, objNum, genNum );
+            }
+        }
+    }
+
+    /**
+     * This will decrypt a stream.
+     *
+     * @param stream The stream to decrypt.
+     * @param objNum The object number.
+     * @param genNum The object generation number.
+     *
+     * @throws CryptographyException If there is an error getting the stream.
+     * @throws IOException If there is an error getting the stream data.
+     */
+    public void decryptStream( COSStream stream, long objNum, long genNum )
+        throws CryptographyException, IOException
+    {
+        decryptDictionary( stream, objNum, genNum );
+        InputStream encryptedStream = stream.getFilteredStream();
+        encryption.encryptData( objNum,
+                                genNum,
+                                encryptionKey,
+                                encryptedStream,
+                                stream.createFilteredStream() );
+    }
+
+    /**
+     * This will decrypt a dictionary.
+     *
+     * @param dictionary The dictionary to decrypt.
+     * @param objNum The object number.
+     * @param genNum The object generation number.
+     *
+     * @throws CryptographyException If there is an error decrypting the document.
+     * @throws IOException If there is an error creating a new string.
+     */
+    private void decryptDictionary( COSDictionary dictionary, long objNum, long genNum )
+        throws CryptographyException, IOException
+    {
+        Iterator keys = dictionary.keyList().iterator();
+        while( keys.hasNext() )
+        {
+            COSName key = (COSName)keys.next();
+            Object value = dictionary.getItem( key );
+            //if we are a signature dictionary and contain a Contents entry then
+            //we don't decrypt it.
+            if( !(key.getName().equals( "Contents" ) && 
+                  value instanceof COSString && 
+                  potentialSignatures.contains( dictionary )))
+            {
+                decrypt( value, objNum, genNum );
+            }
+        }
+    }
+
+    /**
+     * This will decrypt a string.
+     *
+     * @param string the string to decrypt.
+     * @param objNum The object number.
+     * @param genNum The object generation number.
+     *
+     * @throws CryptographyException If an error occurs during decryption.
+     * @throws IOException If an error occurs writing the new string.
+     */
+    public void decryptString( COSString string, long objNum, long genNum )
+        throws CryptographyException, IOException
+    {
+        ByteArrayInputStream data = new ByteArrayInputStream( string.getBytes() );
+        ByteArrayOutputStream buffer = new ByteArrayOutputStream();
+        encryption.encryptData( objNum,
+                                genNum,
+                                encryptionKey,
+                                data,
+                                buffer );
+        string.reset();
+        string.append( buffer.toByteArray() );
+    }
+
+    /**
+     * This will decrypt an array.
+     *
+     * @param array The array to decrypt.
+     * @param objNum The object number.
+     * @param genNum The object generation number.
+     *
+     * @throws CryptographyException If an error occurs during decryption.
+     * @throws IOException If there is an error accessing the data.
+     */
+    private void decryptArray( COSArray array, long objNum, long genNum )
+        throws CryptographyException, IOException
+    {
+        for( int i=0; i<array.size(); i++ )
+        {
+            decrypt( array.get( i ), objNum, genNum );
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/org/pdfbox/encryption/PDFEncryption.java b/src/main/java/org/pdfbox/encryption/PDFEncryption.java
new file mode 100644
index 0000000..5bd3d64
--- /dev/null
+++ b/src/main/java/org/pdfbox/encryption/PDFEncryption.java
@@ -0,0 +1,599 @@
+/**
+ * Copyright (c) 2003-2005, 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 org.pdfbox.encryption;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+import org.pdfbox.exceptions.CryptographyException;
+
+/**
+ * This class will deal with PDF encryption algorithms.
+ *
+ * @author Ben Litchfield (ben@benlitchfield.com)
+ * @version $Revision: 1.13 $
+ */
+public final class PDFEncryption
+{
+    private ARCFour rc4 = new ARCFour();
+    /**
+     * The encryption padding defined in the PDF 1.4 Spec algorithm 3.2.
+     */
+    public static final byte[] ENCRYPT_PADDING =
+    {
+        (byte)0x28, (byte)0xBF, (byte)0x4E, (byte)0x5E, (byte)0x4E,
+        (byte)0x75, (byte)0x8A, (byte)0x41, (byte)0x64, (byte)0x00,
+        (byte)0x4E, (byte)0x56, (byte)0xFF, (byte)0xFA, (byte)0x01,
+        (byte)0x08, (byte)0x2E, (byte)0x2E, (byte)0x00, (byte)0xB6,
+        (byte)0xD0, (byte)0x68, (byte)0x3E, (byte)0x80, (byte)0x2F,
+        (byte)0x0C, (byte)0xA9, (byte)0xFE, (byte)0x64, (byte)0x53,
+        (byte)0x69, (byte)0x7A
+    };
+
+    /**
+     * This will encrypt a piece of data.
+     *
+     * @param objectNumber The id for the object.
+     * @param genNumber The generation id for the object.
+     * @param key The key used to encrypt the data.
+     * @param data The data to encrypt/decrypt.
+     * @param output The stream to write to.
+     *
+     * @throws CryptographyException If there is an error encrypting the data.
+     * @throws IOException If there is an io error.
+     */
+    public final void encryptData(
+        long objectNumber,
+        long genNumber,
+        byte[] key,
+        InputStream data,
+        OutputStream output )
+        throws CryptographyException, IOException
+    {
+        byte[] newKey = new byte[ key.length + 5 ];
+        System.arraycopy( key, 0, newKey, 0, key.length );
+        //PDF 1.4 reference pg 73
+        //step 1
+        //we have the reference
+
+        //step 2
+        newKey[newKey.length -5] = (byte)(objectNumber & 0xff);
+        newKey[newKey.length -4] = (byte)((objectNumber >> 8) & 0xff);
+        newKey[newKey.length -3] = (byte)((objectNumber >> 16) & 0xff);
+        newKey[newKey.length -2] = (byte)(genNumber & 0xff);
+        newKey[newKey.length -1] = (byte)((genNumber >> 8) & 0xff);
+
+
+        //step 3
+        byte[] digestedKey = null;
+        try
+        {
+            MessageDigest md = MessageDigest.getInstance( "MD5" );
+            digestedKey = md.digest( newKey );
+        }
+        catch( NoSuchAlgorithmException e )
+        {
+            throw new CryptographyException( e );
+        }
+
+        //step 4
+        int length = Math.min( newKey.length, 16 );
+        byte[] finalKey = new byte[ length ];
+        System.arraycopy( digestedKey, 0, finalKey, 0, length );
+
+        rc4.setKey( finalKey );
+        rc4.write( data, output );
+        output.flush();
+    }
+
+    /**
+     * This will get the user password from the owner password and the documents o value.
+     *
+     * @param ownerPassword The plaintext owner password.
+     * @param o The document's o entry.
+     * @param revision The document revision number.
+     * @param length The length of the encryption.
+     *
+     * @return The plaintext padded user password.
+     *
+     * @throws CryptographyException If there is an error getting the user password.
+     * @throws IOException If there is an error reading data.
+     */
+    public final byte[] getUserPassword(
+        byte[] ownerPassword,
+        byte[] o,
+        int revision,
+        long length )
+        throws CryptographyException, IOException
+    {
+        try
+        {
+            ByteArrayOutputStream result = new ByteArrayOutputStream();
+
+            //3.3 STEP 1
+            byte[] ownerPadded = truncateOrPad( ownerPassword );
+
+            //3.3 STEP 2
+            MessageDigest md = MessageDigest.getInstance( "MD5" );
+            md.update( ownerPadded );
+            byte[] digest = md.digest();
+
+            //3.3 STEP 3
+            if( revision == 3 || revision == 4 )
+            {
+                for( int i=0; i<50; i++ )
+                {
+                    md.reset();
+                    md.update( digest );
+                    digest = md.digest();
+                }
+            }
+            if( revision == 2 && length != 5 )
+            {
+                throw new CryptographyException(
+                    "Error: Expected length=5 actual=" + length );
+            }
+
+            //3.3 STEP 4
+            byte[] rc4Key = new byte[ (int)length ];
+            System.arraycopy( digest, 0, rc4Key, 0, (int)length );
+
+            //3.7 step 2
+            if( revision == 2 )
+            {
+                rc4.setKey( rc4Key );
+                rc4.write( o, result );
+            }
+            else if( revision == 3 || revision == 4)
+            {
+                /**
+                byte[] iterationKey = new byte[ rc4Key.length ];
+                byte[] dataToEncrypt = o;
+                for( int i=19; i>=0; i-- )
+                {
+                    System.arraycopy( rc4Key, 0, iterationKey, 0, rc4Key.length );
+                    for( int j=0; j< iterationKey.length; j++ )
+                    {
+                        iterationKey[j] = (byte)(iterationKey[j] ^ (byte)i);
+                    }
+                    rc4.setKey( iterationKey );
+                    rc4.write( dataToEncrypt, result );
+                    dataToEncrypt = result.toByteArray();
+                    result.reset();
+                }
+                result.write( dataToEncrypt, 0, dataToEncrypt.length );
+                */
+                byte[] iterationKey = new byte[ rc4Key.length ];
+                
+              
+                byte[] otemp = new byte[ o.length ]; //sm 
+                System.arraycopy( o, 0, otemp, 0, o.length ); //sm
+                rc4.write( o, result);//sm
+                
+                for( int i=19; i>=0; i-- )
+                {
+                    System.arraycopy( rc4Key, 0, iterationKey, 0, rc4Key.length );
+                    for( int j=0; j< iterationKey.length; j++ )
+                    {
+                        iterationKey[j] = (byte)(iterationKey[j] ^ (byte)i);
+                    }
+                    rc4.setKey( iterationKey );
+                    result.reset();  //sm
+                    rc4.write( otemp, result ); //sm
+                    otemp = result.toByteArray(); //sm                
+                }
+            }
+
+
+            return result.toByteArray();
+
+        }
+        catch( NoSuchAlgorithmException e )
+        {
+            throw new CryptographyException( e );
+        }
+    }
+
+    /**
+     * This will tell if this is the owner password or not.
+     *
+     * @param ownerPassword The plaintext owner password.
+     * @param u The U value from the PDF Document.
+     * @param o The owner password hash.
+     * @param permissions The document permissions.
+     * @param id The document id.
+     * @param revision The revision of the encryption.
+     * @param length The length of the encryption key.
+     *
+     * @return true if the owner password matches the one from the document.
+     *
+     * @throws CryptographyException If there is an error while executing crypt functions.
+     * @throws IOException If there is an error while checking owner password.
+     */
+    public final boolean isOwnerPassword(
+        byte[] ownerPassword,
+        byte[] u,
+        byte[] o,
+        int permissions,
+        byte[] id,
+        int revision,
+        int length)
+        throws CryptographyException, IOException
+    {
+        byte[] userPassword = getUserPassword( ownerPassword, o, revision, length );
+        return isUserPassword( userPassword, u, o, permissions, id, revision, length );
+    }
+
+    /**
+     * This will tell if this is a valid user password.
+     *
+     * Algorithm 3.6 pg 80
+     *
+     * @param password The password to test.
+     * @param u The U value from the PDF Document.
+     * @param o The owner password hash.
+     * @param permissions The document permissions.
+     * @param id The document id.
+     * @param revision The revision of the encryption.
+     * @param length The length of the encryption key.
+     *
+     * @return true If this is the correct user password.
+     *
+     * @throws CryptographyException If there is an error computing the value.
+     * @throws IOException If there is an IO error while computing the owners password.
+     */
+    public final boolean isUserPassword(
+        byte[] password,
+        byte[] u,
+        byte[] o,
+        int permissions,
+        byte[] id,
+        int revision,
+        int length)
+        throws CryptographyException, IOException
+    {
+        boolean matches = false;
+        //STEP 1
+        byte[] computedValue = computeUserPassword( password, o, permissions, id, revision, length );
+        if( revision == 2 )
+        {
+            //STEP 2
+            matches = arraysEqual( u, computedValue );
+        }
+        else if( revision == 3 || revision == 4 )
+        {
+            //STEP 2
+            matches = arraysEqual( u, computedValue, 16 );
+        }
+        return matches;
+    }
+
+    /**
+     * This will compare two byte[] for equality for count number of bytes.
+     *
+     * @param first The first byte array.
+     * @param second The second byte array.
+     * @param count The number of bytes to compare.
+     *
+     * @return true If the arrays contain the exact same data.
+     */
+    private final boolean arraysEqual( byte[] first, byte[] second, int count )
+    {
+        boolean equal = first.length >= count && second.length >= count;
+        for( int i=0; i<count && equal; i++ )
+        {
+            equal = first[i] == second[i];
+        }
+        return equal;
+    }
+
+    /**
+     * This will compare two byte[] for equality.
+     *
+     * @param first The first byte array.
+     * @param second The second byte array.
+     *
+     * @return true If the arrays contain the exact same data.
+     */
+    private final boolean arraysEqual( byte[] first, byte[] second )
+    {
+        boolean equal = first.length == second.length;
+        for( int i=0; i<first.length && equal; i++ )
+        {
+            equal = first[i] == second[i];
+        }
+        return equal;
+    }
+
+    /**
+     * This will compute the user password hash.
+     *
+     * @param password The plain text password.
+     * @param o The owner password hash.
+     * @param permissions The document permissions.
+     * @param id The document id.
+     * @param revision The revision of the encryption.
+     * @param length The length of the encryption key.
+     *
+     * @return The user password.
+     *
+     * @throws CryptographyException If there is an error computing the user password.
+     * @throws IOException If there is an IO error.
+     */
+    public final byte[] computeUserPassword(
+        byte[] password,
+        byte[] o,
+        int permissions,
+        byte[] id,
+        int revision,
+        int length )
+        throws CryptographyException, IOException
+    {
+        ByteArrayOutputStream result = new ByteArrayOutputStream();
+        //STEP 1
+        byte[] encryptionKey = computeEncryptedKey( password, o, permissions, id, revision, length );
+
+        if( revision == 2 )
+        {
+            //STEP 2
+            rc4.setKey( encryptionKey );
+            rc4.write( ENCRYPT_PADDING, result );
+        }
+        else if( revision == 3 || revision == 4 )
+        {
+            try
+            {
+                //STEP 2
+                MessageDigest md = MessageDigest.getInstance("MD5");
+                //md.update( truncateOrPad( password ) );
+                md.update( ENCRYPT_PADDING );
+
+                //STEP 3
+                md.update( id );
+                result.write( md.digest() );
+
+                //STEP 4 and 5
+                byte[] iterationKey = new byte[ encryptionKey.length ];
+                for( int i=0; i<20; i++ )
+                {
+                    System.arraycopy( encryptionKey, 0, iterationKey, 0, iterationKey.length );
+                    for( int j=0; j< iterationKey.length; j++ )
+                    {
+                        iterationKey[j] = (byte)(iterationKey[j] ^ i);
+                    }
+                    rc4.setKey( iterationKey );
+                    ByteArrayInputStream input = new ByteArrayInputStream( result.toByteArray() );
+                    result.reset();
+                    rc4.write( input, result );
+                }
+
+                //step 6
+                byte[] finalResult = new byte[32];
+                System.arraycopy( result.toByteArray(), 0, finalResult, 0, 16 );
+                System.arraycopy( ENCRYPT_PADDING, 0, finalResult, 16, 16 );
+                result.reset();
+                result.write( finalResult );
+            }
+            catch( NoSuchAlgorithmException e )
+            {
+                throw new CryptographyException( e );
+            }
+        }
+        return result.toByteArray();
+    }
+
+    /**
+     * This will compute the encrypted key.
+     *
+     * @param password The password used to compute the encrypted key.
+     * @param o The owner password hash.
+     * @param permissions The permissions for the document.
+     * @param id The document id.
+     * @param revision The security revision.
+     * @param length The length of the encryption key.
+     *
+     * @return The encryption key.
+     *
+     * @throws CryptographyException If there is an error computing the key.
+     */
+    public final byte[] computeEncryptedKey(
+        byte[] password,
+        byte[] o,
+        int permissions,
+        byte[] id,
+        int revision,
+        int length )
+        throws CryptographyException
+    {
+        byte[] result = new byte[ length ];
+        try
+        {
+            //PDFReference 1.4 pg 78
+            //step1
+            byte[] padded = truncateOrPad( password );
+
+            //step 2
+            MessageDigest md = MessageDigest.getInstance("MD5");
+            md.update( padded );
+
+            //step 3
+            md.update( o );
+
+            //step 4
+            byte zero = (byte)(permissions >>> 0);
+            byte one = (byte)(permissions >>> 8);
+            byte two = (byte)(permissions >>> 16);
+            byte three = (byte)(permissions >>> 24);
+
+            md.update( zero );
+            md.update( one );
+            md.update( two );
+            md.update( three );
+
+            //step 5
+            md.update( id );
+            byte[] digest = md.digest();
+
+            //step 6
+            if( revision == 3 || revision == 4)
+            {
+                for( int i=0; i<50; i++ )
+                {
+                    md.reset();
+                    md.update( digest, 0, length );
+                    digest = md.digest();
+                }
+            }
+
+            //step 7
+            if( revision == 2 && length != 5 )
+            {
+                throw new CryptographyException(
+                    "Error: length should be 5 when revision is two actual=" + length );
+            }
+            System.arraycopy( digest, 0, result, 0, length );
+        }
+        catch( NoSuchAlgorithmException e )
+        {
+            throw new CryptographyException( e );
+        }
+        return result;
+    }
+
+    /**
+     * This algorithm is taked from PDF Reference 1.4 Algorithm 3.3 Page 79.
+     *
+     * @param ownerPassword The plain owner password.
+     * @param userPassword The plain user password.
+     * @param revision The version of the security.
+     * @param length The length of the document.
+     *
+     * @return The computed owner password.
+     *
+     * @throws CryptographyException If there is an error computing O.
+     * @throws IOException If there is an error computing O.
+     */
+    public final byte[] computeOwnerPassword(
+        byte[] ownerPassword,
+        byte[] userPassword,
+        int revision,
+        int length )
+        throws CryptographyException, IOException
+    {
+        try
+        {
+            //STEP 1
+            byte[] ownerPadded = truncateOrPad( ownerPassword );
+
+            //STEP 2
+            MessageDigest md = MessageDigest.getInstance( "MD5" );
+            md.update( ownerPadded );
+            byte[] digest = md.digest();
+
+            //STEP 3
+            if( revision == 3 || revision == 4)
+            {
+                for( int i=0; i<50; i++ )
+                {
+                    md.reset();
+                    md.update( digest, 0, length );
+                    digest = md.digest();
+                }
+            }
+            if( revision == 2 && length != 5 )
+            {
+                throw new CryptographyException(
+                    "Error: Expected length=5 actual=" + length );
+            }
+
+            //STEP 4
+            byte[] rc4Key = new byte[ length ];
+            System.arraycopy( digest, 0, rc4Key, 0, length );
+
+            //STEP 5
+            byte[] paddedUser = truncateOrPad( userPassword );
+
+
+            //STEP 6
+            rc4.setKey( rc4Key );
+            ByteArrayOutputStream crypted = new ByteArrayOutputStream();
+            rc4.write( new ByteArrayInputStream( paddedUser ), crypted );
+
+
+            //STEP 7
+            if( revision == 3 || revision == 4 )
+            {
+                byte[] iterationKey = new byte[ rc4Key.length ];
+                for( int i=1; i<20; i++ )
+                {
+                    System.arraycopy( rc4Key, 0, iterationKey, 0, rc4Key.length );
+                    for( int j=0; j< iterationKey.length; j++ )
+                    {
+                        iterationKey[j] = (byte)(iterationKey[j] ^ (byte)i);
+                    }
+                    rc4.setKey( iterationKey );
+                    ByteArrayInputStream input = new ByteArrayInputStream( crypted.toByteArray() );
+                    crypted.reset();
+                    rc4.write( input, crypted );
+                }
+            }
+
+            //STEP 8
+            return crypted.toByteArray();
+        }
+        catch( NoSuchAlgorithmException e )
+        {
+            throw new CryptographyException( e.getMessage() );
+        }
+    }
+
+    /**
+     * This will take the password and truncate or pad it as necessary.
+     *
+     * @param password The password to pad or truncate.
+     *
+     * @return The padded or truncated password.
+     */
+    private final byte[] truncateOrPad( byte[] password )
+    {
+        byte[] padded = new byte[ ENCRYPT_PADDING.length ];
+        int bytesBeforePad = Math.min( password.length, padded.length );
+        System.arraycopy( password, 0, padded, 0, bytesBeforePad );
+        System.arraycopy( ENCRYPT_PADDING, 0, padded, bytesBeforePad, ENCRYPT_PADDING.length-bytesBeforePad );
+        return padded;
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/org/pdfbox/encryption/package.html b/src/main/java/org/pdfbox/encryption/package.html
new file mode 100644
index 0000000..62bc982
--- /dev/null
+++ b/src/main/java/org/pdfbox/encryption/package.html
@@ -0,0 +1,9 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
+<html>
+<head>
+
+</head>
+<body>
+These classes deal with encryption algorithms that are used in the PDF Document.
+</body>
+</html>
-- 
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