All posts by mfeilner Which Key length/cipher to use for a certain period of time

Reality update: Keylength – Compare all Methods … :

This web site implements mathematical formulas and summarizes reports from well-known organizations allowing you to quickly evaluate the minimum security requirements for your system. You can also easily compare all these techniques and find the appropriate key length for your desired level of protection. The lengths provided here are designed to resist mathematic attacks; they do not take algorithmic attacks, hardware flaws, etc. into account.

Quick PDF conversion with convert blocked? [Solved]

Very recently I had to convert a PDF (i.e. concatenate three PDFs into one file) and I was blocked for security reasons. 

convert *pdf complete.pdf usually adds the files it finds in alphanumerical order to complete.pdf.

But not this time: 

“convert: attempt to perform an operation not allowed by the security policy `PDF’ @ error/constitute.c/IsCoderAuthorized/408.”

Googling helped, as it often does, and I found this hint at [Imagemagick security policy ‘PDF’ blocking conversion – Stack Overflow] … :

Well, I added

  <policy domain=”coder” rights=”read | write” pattern=”PDF” />

I added just before in /etc/ImageMagick-7/policy.xml and that makes it work again, but not sure about the security implications of that.”

A comment says that was a Ghostscript vulnerability, but new gs-versions are fine. Let’s hope that’s true…:-)


Since the convert process resulted in bad quality (after I applied the changes above), I had to do some more homework and play with the values of this convert command: 

convert -density 200 -trim [Input_PDF_Files]* -quality 50 output.pdf

In my setup, that ends up with decent quality but 2.5 MByte per page.