org.verapdf.tools

Class EncryptionToolsRevision4

java.lang.Object

org.verapdf.tools.EncryptionToolsRevision4

public class EncryptionToolsRevision4
extends Object

Contains methods for encryption and decryption of PDF files.

Author:

Sergey Shemyakov

Method Summary

Modifier and Type	Method and Description
static byte[]	authenticateUserPassword(String password, byte[] o, int p, byte[] id, int revision, boolean metadataIsEncrypted, int length, byte[] u) Authenticates user password and returns encryption key if password is correct.
static byte[]	computeEncryptionKey(String password, byte[] o, int p, byte[] id, int revision, boolean metadataIsEncrypted, int length) Method computes encryption key for given data as specified in 7.6.3.3.
static byte[]	computeOValue(String ownerPassword, int revision, int length, String userPassword) Method computes O value in standard encryption dict for standard security handler as specified in 7.6.3.4.
static byte[]	computeUValue(String password, byte[] o, int p, byte[] id, int revision, boolean metadataIsEncrypted, int length) Method computes U value in standard encryption dict for standard security handler as specified in 7.6.3.4.
static byte[]	intToBytesLowOrderFirst(long p) Represents given integer as byte array where low-order bytes go first.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

computeEncryptionKey

public static byte[] computeEncryptionKey(String password,
                                          byte[] o,
                                          int p,
                                          byte[] id,
                                          int revision,
                                          boolean metadataIsEncrypted,
                                          int length)
                                   throws NoSuchAlgorithmException

Method computes encryption key for given data as specified in 7.6.3.3. Algorithm 2 of PDF32000_2008.

Parameters:

password - is password string.

o - is O value of encryption dict for standard security handler.

p - is P value of encryption dict for standard security handler.

id - is the value of the ID entry in the document’s trailer dict.

revision - is R value of encryption dict for standard security handler.

metadataIsEncrypted - is true if metadata in file is encrypted.

length - is value of Length in encryption dict.

Returns:

encryption key.

Throws:

NoSuchAlgorithmException

computeOValue

public static byte[] computeOValue(String ownerPassword,
                                   int revision,
                                   int length,
                                   String userPassword)
                            throws NoSuchAlgorithmException

Method computes O value in standard encryption dict for standard security handler as specified in 7.6.3.4. Algorithm 3 of PDF32000_2008.

Parameters:

ownerPassword - is owner password.

revision - is R value of encryption dict for standard security handler.

length - is value of Length in encryption dict.

userPassword - is user password.

Returns:

value of O for encryption dict for standard security handler.

Throws:

NoSuchAlgorithmException

computeUValue

public static byte[] computeUValue(String password,
                                   byte[] o,
                                   int p,
                                   byte[] id,
                                   int revision,
                                   boolean metadataIsEncrypted,
                                   int length)
                            throws NoSuchAlgorithmException

Method computes U value in standard encryption dict for standard security handler as specified in 7.6.3.4. Algorithm 4 and 5 of PDF32000_2008.

Parameters:

password - is user password.

o - is O value of encryption dict for standard security handler.

p - is P value of encryption dict for standard security handler.

id - is the value of the ID entry in the document’s trailer dict.

revision - is R value of encryption dict for standard security handler.

metadataIsEncrypted - is true if metadata in file is encrypted.

length - is value of Length in encryption dict.

Returns:

value of U for encryption dict for standard security handler.

Throws:

NoSuchAlgorithmException

authenticateUserPassword

public static byte[] authenticateUserPassword(String password,
                                              byte[] o,
                                              int p,
                                              byte[] id,
                                              int revision,
                                              boolean metadataIsEncrypted,
                                              int length,
                                              byte[] u)
                                       throws NoSuchAlgorithmException

Authenticates user password and returns encryption key if password is correct.

Parameters:

password - is string to be checked.

o - is O value of encryption dict for standard security handler.

p - is P value of encryption dict for standard security handler.

id - is the value of the ID entry in the document’s trailer dict.

revision - is R value of encryption dict for standard security handler.

metadataIsEncrypted - is true if metadata in file is encrypted.

length - is value of Length in encryption dict.

u - is U value of encryption dict for standard security handler.

Returns:

null if password is incorrect and encryption key if it is correct.

Throws:

NoSuchAlgorithmException

intToBytesLowOrderFirst

public static byte[] intToBytesLowOrderFirst(long p)

Represents given integer as byte array where low-order bytes go first.

Parameters:

p - is integer.

Returns:

array of 4 bytes that represent this number as unsigned 32-bit integer, low-order bytes go first.