com.sun.pdfview.decrypt

Interface PDFDecrypter

All Known Implementing Classes:

CryptFilterDecrypter, IdentityDecrypter, StandardDecrypter

public interface PDFDecrypter

A decrypter decrypts streams and strings in a PDF document. decryptBuffer(String, PDFObject, ByteBuffer) } should be used for decoding streams, and decryptString(int, int, String) for string values in the PDF. It is possible for strings and streams to be encrypted with different mechanisms, so the appropriate method must alwayus be used.

Author:

Luke Kirby

See Also:

"PDFReference 1.7, Section 3.5 Encryption"

Method Summary

Modifier and Type	Method and 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	isOwnerAuthorised() Determine whether the password known by the decrypter indicates that the user is the owner of the document.

Method Detail

decryptBuffer

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

Decrypt a buffer of data

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 the named crypt filter does not exist, or if a crypt filter is named when named crypt filters are not supported. Problems due to incorrect passwords are revealed prior to this point.

decryptString

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

Decrypt a basic string.

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 the named crypt filter does not exist, or if a crypt filter is named when named crypt filters are not supported. Problems due to incorrect passwords are revealed prior to this point.

isOwnerAuthorised

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 isEncryptionPresent() to determine whether any permissions apply.

Returns:

whether owner authentication is being used to decrypt the document

isEncryptionPresent

boolean isEncryptionPresent()

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

Returns:

whether encryption is present