Package org.loboevolution.pdfview.decrypt

Class StandardDecrypter

java.lang.Object

org.loboevolution.pdfview.decrypt.StandardDecrypter

All Implemented Interfaces:

PDFDecrypter

public class StandardDecrypter
extends Object
implements PDFDecrypter

Standard simple decrypter for versions 1, 2 and 4 of the Standard password-based decryption mechanisms, as described in section 3.5 of the PDF Reference version 1.7.

Author Luke Kirby

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static enum	StandardDecrypter.EncryptionAlgorithm	Describes an encryption algorithm to be used, declaring not only the cipher type, but also key generation techniques

Constructor Summary

Constructors

Constructor	Description
StandardDecrypter(StandardDecrypter.EncryptionAlgorithm encryptionAlgorithm, PDFObject documentId, int keyBitLength, int revision, byte[] oValue, byte[] uValue, int pValue, boolean encryptMetadata, PDFPassword password)	Class constructor

Method Summary

Modifier and Type	Method	Description
ByteBuffer	decryptBuffer(String cryptFilterName, PDFObject streamObj, ByteBuffer streamBuf)	Decrypt a buffer of data
String	decryptString(int objNum, int objGen, String inputBasicString)	Decrypt a basic string.
boolean	isEncryptionPresent()	Determine whether this actually applies a decryption other than identity decryption.
boolean	isEncryptionPresent(String cryptFilterName)	Determines whether decryption applies for a given crypt filter name
boolean	isOwnerAuthorised()	Determine whether the password known by the decrypter indicates that the user is the owner of the document.

Methods inherited from class java.lang.Object

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

Constructor Details

StandardDecrypter

public StandardDecrypter(StandardDecrypter.EncryptionAlgorithm encryptionAlgorithm,
 PDFObject documentId,
 int keyBitLength,
 int revision,
 byte[] oValue,
 byte[] uValue,
 int pValue,
 boolean encryptMetadata,
 PDFPassword password)
                  throws IOException,
EncryptionUnsupportedByProductException,
EncryptionUnsupportedByPlatformException

Class constructor

Parameters:

encryptionAlgorithm - the algorithm used for encryption

documentId - the contents of the ID entry of the document's trailer dictionary; can be null, but according to the spec, shouldn't be. Is expected to be an array of two byte sequences.

keyBitLength - the length of the key in bits; should be a multiple of 8 between 40 and 128

revision - the revision of the Standard encryption security handler being employed. Should be 2, 3 or 4.

oValue - the value of the O entry from the Encrypt dictionary

uValue - the value of the U entry from the Encrypt dictionary

pValue - the value of the P entry from the Encrypt dictionary

encryptMetadata - whether metadata is being encrypted, as identified by the Encrypt dict (with default true if not explicitly identified)

password - the password; not null

Throws:

IOException - if any.

EncryptionUnsupportedByProductException - if any.

EncryptionUnsupportedByPlatformException - if any.

Method Details

decryptBuffer

public ByteBuffer decryptBuffer(String cryptFilterName,
 PDFObject streamObj,
 ByteBuffer streamBuf)
                         throws PDFParseException

Decrypt a buffer of data

Specified by:

decryptBuffer in interface PDFDecrypter

Parameters:

cryptFilterName - the name of the crypt filter, if V4 encryption is being used, where individual crypt filters may be specified for individual streams. If encryption is not using V4 encryption (indicated by V=4 in the Encrypt dictionary) then this must be null. Null may also be specified with V4 encryption to indicate that the default filter should be used.

streamObj - the object whose stream is being decrypted. The containing object's number and generation contribute to the key used for stream encrypted with the document's default encryption, so this is typically required. Should be null only if a cryptFilterName is specified, as objects with specific stream filters use the general document key, rather than a stream-specific key.

streamBuf - the buffer to decrypt

Returns:

a buffer containing the decrypted stream, positioned at its beginning; will only be the same buffer as streamBuf if the identity decrypter is being used

Throws:

PDFParseException - if any.

decryptString

public String decryptString(int objNum,
 int objGen,
 String inputBasicString)
                     throws PDFParseException

Decrypt a basic string.

Specified by:

decryptString in interface PDFDecrypter

Parameters:

objNum - the object number of the containing object

objGen - the generation number of the containing object

inputBasicString - the string to be decrypted

Returns:

the decrypted string

Throws:

PDFParseException - if any.

isOwnerAuthorised

public boolean isOwnerAuthorised()

Determine whether the password known by the decrypter indicates that the user is the owner of the document. Can be used, in conjunction with PDFDecrypter.isEncryptionPresent() to determine whether any permissions apply.

Specified by:

isOwnerAuthorised in interface PDFDecrypter

Returns:

whether owner authentication is being used to decrypt the document

isEncryptionPresent

public boolean isEncryptionPresent()

Determine whether this actually applies a decryption other than identity decryption.

Specified by:

isEncryptionPresent in interface PDFDecrypter

Returns:

whether encryption is present

isEncryptionPresent

public boolean isEncryptionPresent(String cryptFilterName)

Determines whether decryption applies for a given crypt filter name

Specified by:

isEncryptionPresent in interface PDFDecrypter

Parameters:

cryptFilterName - the crypt filter name

Returns:

whether the given crypt filter decrypts or not