Package org.loboevolution.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.

see "PDFReference 1.7, Section 3.5 Encryption" Author Luke Kirby

  • Method Details

    • 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 any.

    • 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 any.

    • 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

    • isEncryptionPresent

      boolean isEncryptionPresent(String cryptFilterName)
      Determines whether decryption applies for a given crypt filter name
      Parameters:
      cryptFilterName - the crypt filter name
      Returns:
      whether the given crypt filter decrypts or not