pdf links

PDF Rendering
Convert PDF to Image (.NET)
Convert PDF to image on Android (Xamarin)
Convert PDF to image on iOS (Xamarin)
Convert PDF to image in Windows Store apps (.NET)
Convert PDF to image in Windows Phone apps (.NET)
PDF to image in Universal Windows Store apps (.NET)
Free PDF Viewer control for Windows Forms (.NET)
How to integrate PDF Viewer control in WPF app (.NET)
Creating WPF PDF Viewer supporting bookmarks (.NET)
Cross-platform PDF Viewer using GTK# (MONO)
Silverlight PDF viewer control (Silverlight 5)
Multithreaded PDF rendering (.NET)
Convert pdf to image in Silverlight app (C# sample)
How to set fallback fonts for PDF rendering (C#)
Avoiding the out-of-memory exception on rendering (C#)
PDF viewer single page application (WebAPI, AngularJS)
PDF viewer control for Windows 10 universal applications
Use custom ICC profile for CMYK to RGB conversion
PDF layers - separate images, text, annotations, graphics

PDF Forms Creation PDF Security
Conversion to PDF/A
Other topics
PDF Document Manipulation
PDF Content Generation
Fixed and Flow layout document API (.NET)
Creation of grids and tables in PDF (C# sample)
How to create interactive documents using Actions (C# sample)
Text flow effects in PDF (C# sample)
How to generate ordered and bulleted lists in PDF (C# sample)
Convert HTML to PDF using flow layout API (C# sample)
How to use custom fonts for PDF generation (.NET)
Create document with differently sized pages (C#)
Create PDF documents using MONO (C#/MONO/Windows/OSX)
How to use background images for content elements (C#/PDF Kit/FlowLayout)
Add transparent images to PDF document (C#)
Draw round rect borders in PDF documents(C#)
ICC color profiles and and ICC based colors in PDF (C#)
How to use bidirectional and right to left text in PDF (C#)
Create PDF documents from XML templates (C# sample)
How to resize PDF pages and use custom stamps (C#)
Add header and footer to PDF page (.NET sample)
How to use clipping mask for drawing on PDF page
Fill graphics path with gradient brushes in PDF (Shadings)
Apitron PDF Kit and Rasterizer engine settings
Add layers to PDF page (optional content, C# sample)
How to create free text annotation with custom appearance

PDF Content Extraction
PDF Navigation

PDF to TIFF conversion
Contact us if you have a PDF related question and we'll cover it in our blog.


Long-term validation of signatures in PDF documents or LTV enabled signatures



Long-term validation of signatures in PDF documents is a mechanism to check that the signature and all related certificates are still valid at the time of checking (opening the doc) without making any requests to the signing authorities. That is all required information including OCSP responses, CRLs and timestamp should be present into the document.

Checking long term validation state

So, how can you check if the file you're viewing has LTV enabled signatures? See the image below that demonstrates that:

LTV-enabled signature  
Pic.1 LTV-enabled signature

Basically PDF reader makes the check for you and displays the "Signature is LTV enabled" message. It also says that the signature is timestamped and it's very important because it proves that the file was signed at specific time and the clock couldn't be manipulated to produce the signature. Another way to check if the signature is LTV enabled is by examining whether the certificates' revocation info is embedded into the document. To do this, open signature properties window and check certs from the certificate chain one by one, you should see the similar picture:

Checking certificate revocation info status
Pic.2 Checking certificate revocation info status

Additionally, you can take a look at advanced signature properties to find the timestamping authority details, hash algorithm used and producer info.

Advanced signature properties
Pic.3 Advanced signature properties



While LTV can be tricky to implement sometimes, we have invaluable experience in that area and our products are ready to process LTV enabled documents as well.  So if you need any help with implementing digital signatures workflow, just let us know and we'll be happy to come up with a solution for you.

No comments:

Post a Comment