('binary' encoding is not supported, stored as-is) In-Reply-To: <98A3855A9087D411952F00508B61BD40046F02CAat_private> >If the PDF requires a password to open, I'm not sure you can do anything >about cracking it, other than brute forcing the password (haven't looked for >any tools for this) You can. For Acrobat 4.x files (PDF 1.3 specification), encryption key (RC4) is 40 bits only -- so it's possible to try all 40-bit keys instead of all passwords. With the good low-level optimization, trying one key takes only about 1,000 CPU circles (on P6), so complete recovery would take only a few days. On dual-CPU system with Athlon MP 1800+, our software does that is maximum 4 days, regardless password length and complexity! Acrobat 5.x, however, can use 128-bit RC4 encryption, so it is not possible to try all the keys. >If the PDF is openable and viewable, but is "protected", so that you can't >select or print or annotate, that is easily bypassed with almost any >non-Adobe PDF viewer, such as xpdf, which simply elects not to honour that >setting in the PDF. The data is all there, because you can view it, it is >simply a case of the software choosing to not let you select it. No exactly. Even if the document is openable, but you cannot copy or print -- it is really encrypted using with the same algorithm (RC4). However, decryption key can be calculated from the document (PDF Info Dictionary records). /Vladimir http://pdf.elcomsoft.com
This archive was generated by hypermail 2b30 : Fri May 17 2002 - 09:09:41 PDT