Previous Next

                                        1103
S E C T I O N H .3                                             Implementation Notes



3.5, “Encryption”
  22. An option to use an unpublished algorithm was needed because of an ex-
      port requirement of the U.S. Department of Commerce. This requirement
      no longer exists. Acrobat 7.0 does not use this algorithm to encrypt docu-
      ments, although it can decrypt files that are encrypted with the algorithm.
  23. Acrobat viewers will fail to open a document encrypted with a V value de-
      fined in a version of PDF that the viewer does not understand.
  24. Security handlers are responsible for protecting the value of EFF from
      tampering if needed. Acrobat security handlers do not provide this pro-
      tection.


3.5.2, “Standard Security Handler” (Standard Encryption Dictionary)
  25. Acrobat viewers implement this limited mode of printing as “Print As Im-
      age,” except on UNIX systems, where this feature is not available.


3.5.2, “Standard Security Handler” (Encryption Key Algorithm)
  26. The first element of the ID array generally remains the same for a given
      document. However, in some situations, Acrobat may regenerate the ID
      array if a new generation of a document is created. Security handlers are
      encouraged not to rely on the ID in the encryption key computation.


3.5.2, “Standard Security Handler” (Password Algorithms)
  27. In Acrobat 2.0 and 2.1 viewers, the standard security handler uses the
      empty string if there is no owner password in step 1 of Algorithm 3.3.

3.5.4, “Crypt Filters”
  28. In Acrobat 6.0, crypt filter usage is limited to allowing document-level
      metadata streams to be left as plaintext in an otherwise encrypted docu-
      ment. In Acrobat 7.0, crypt filter usage also includes the ability to encrypt
      embedded files while leaving the remainder of the document as plaintext.
  29. In Acrobat 6.0 and later, when strings and streams in an encrypted docu-
      ment are edited, those streams and strings are encrypted with the StmF
      and StrF filters, respectively. In Acrobat 7.0, if the EFF entry in the encryp-
      tion dictionary is set, embedded files are encrypted with the crypt filter

Previous Next