The open source [iTextSharp][1] library will allow you to do this. Here&#39;s a [post][2] explaining how to digitally sign a pdf file. If you don&#39;t want to use a third party library then you can implement it yourself but it could be a tough task -&gt; you can start by reading the [pdf specification][3] (8.6MB)


  [1]: http://itextsharp.sourceforge.net/
  [2]: http://www.codeproject.com/Articles/14488/E-signing-PDF-documents-with-iTextSharp
  [3]: http://www.adobe.com/devnet/acrobat/pdfs/PDF32000_2008.pdf

Proper PDF signing is a *very* sophisticated task. There exist a number of files that don&#39;t conform to the PDF specification (broken xrefs etc) and your code must handle all of them. Then various Acrobat versions treat certain things in signed fields differently. So if you need to do the task (rather than study how it works) you should rely on third-party solution, such as our &lt;a href=&quot;http://www.eldos.com/sbbdev/net-pdf.php&quot;&gt;PDFBlackbox&lt;/a&gt; components.

Digitally signing a PDF document without using a third-party component entails a great deal of work and is generally best avoided.

Components do all the hard work for you, so you don&#39;t have to. You should find there are some excellent free PDF components available that will suit your needs.

The following example written in C# shows how simple it is to digitally sign a PDF document using ABCpdf:

    Doc theDoc = new Doc();
    theDoc.Read(Server.MapPath(&quot;../Rez/Authorization.pdf&quot;));
    Signature theSig = (Signature)theDoc.Form[&quot;Signature&quot;];
    theSig.Location = &quot;Washington&quot;;
    theSig.Reason = &quot;Schedule Agreed&quot;;
    theSig.Sign(Server.MapPath(&quot;../Rez/JohnSmith.pfx&quot;), &quot;111111&quot;);
    theDoc.Save(Server.MapPath(&quot;Signed.pdf&quot;));


Source: [ABCpdf documentation - Sign method][1]

  [1]: http://www.websupergoo.com/helppdf7net/source/6-abcpdf6.objects/signature/1-methods/sign.htm

Lost my first answer.  May want to give DocQ a try to [link text][1]  They have their own cert and can do this for you for free/cheap to seal and encrypt PDFs.  They also have an API you can use.  


  [1]: https://docq.com/ &quot;digitally sign a PDF&quot;

I want find the index of a given DOM node. It&#39;s like the inverse of doing 

    document.getElementById(&#39;id_of_element&#39;).childNodes[K]

I want to instead extract the value of `K` given that I already have the reference to the child node and the parent node. How do I do this? 

Finding DOM node index

I&#39;m getting a NullPointerException in a Class from a 3rd party library. Now I&#39;d like to debug the whole thing and I would need to know from which object the class is held. But it seems to me that I cannot set a breakpoint in a Class from a 3rd party. 

Does anyone know a way out of my trouble? Of course I&#39;m using Eclipse as my IDE.

Update: the library is open-source.

How to set a breakpoint in Eclipse in a third party library?

I have a digital certificate that identifies an user. I need to use it to Digitally sign pdf files.

Does anyone have an example that does not uses a third party component? I need to get this done but it would be nice to fully understand how things are done.

C# Examples please :)

Digitally sign PDF files

I have a digital certificate that identifies an user. I need to use it to Digitally sign pdf files.
Does anyone have an example that does not uses a third party component? I need to get this done but it would be nice to fully understand how things are done.
C# Examples please :)

I have a string `User name (sales)` and I want to extract the text between the brackets, how would I do this? 

I suspect sub-string but I can&#39;t work out how to read until the closing bracket, the length of text will vary.


How do I extract text that lies between parentheses (round brackets)?

I just recently noticed `Dictionary.TryGetValue(TKey key, out TValue value)` and was curious as to which is the better approach to retrieving a value from the Dictionary.

I&#39;ve traditionally done:

    if (myDict.Contains(someKey))
         someVal = myDict[someKey];
         ...


unless I know it _has_ to be in there.

Is it better to just do:

    if (myDict.TryGetValue(somekey, out someVal)
        ...

Which is the better practice? Is one faster than the other? I would imagine that the Try version would be slower as its &#39;swallowing&#39; a try/catch inside itself and using that as logic, no?

Retrieving Dictionary Value Best Practices

Is it possible to pass a function as a parameter in C#? I can do it using the Func or Action classes, but this forces me to declare the entire function signature at once. When I try to use Delegate, I get a compile error saying it can&#39;t convert a method group to a Delegate. 

I&#39;m working on [Axial][1] and I&#39;m trying to allow users to call web services. What I&#39;m going for is the ability to create the Visual Studio proxy class and then pass in the generated function. The function signature doesn&#39;t matter because the generated code only uses the function name. However, I&#39;d like to pass in the function instead of the name for two reasons: the ability to use the proxy&#39;s Url property and a compiler error if the web service doesn&#39;t exist or is updated in Visual Studio.

&lt;pre&gt;&lt;code&gt;
public void AlertIt(object o) {
    Axial.DOM.Window.Alert(o.ToString());
}
public void CallAddService() {
    object[] param = new object[] { int.Parse(txtA.Text), int.Parse(txtB.Text) };
    Axial.ServerScript.CallWebService(new WSProxy.WS().Add, param, AlertIt, AlertIt);
}

class Axial.ServerScript {
    public void CallWebService(Delegate method, object[] param, Action&amp;lt;object&amp;gt; successCallback, Action&amp;lt;object&amp;gt; failureCallback) {
        // translate to javascript (already working)
    }
}
&lt;/code&gt;&lt;/pre&gt;


  [1]: http://www.codeplex.com/axial

How to pass a function as a parameter in C#?

I need an equivalent to c++&#39;s `std::multimap&lt;K, V, Comp, Alloc&gt;` in C-sharp. Does it exist in the standard library?

multimap in .NET

Closed as exact duplicate of [this question][1].

I have an array/list of elements. I want to convert it to a string, separated by a custom delimitator. For example:

    [1,2,3,4,5] =&gt; &quot;1,2,3,4,5&quot;

What&#39;s the shortest/esiest way to do this in c#?

I have always done this by cycling the list and checking if the current element is not the last one before adding the separator.

    for(int i=0; i&lt;arr.Length; ++i)
    {
        str += arr[i].ToString();
        if(i&lt;arr.Length)
            str += &quot;,&quot;;
    }

Is there a LINQ function that can help me write less code?


  [1]: https://stackoverflow.com/questions/145856

Shortest method to convert an array to a string in c#/LINQ

I have an HTML (not XHTML) document that renders fine in Firefox 3 and IE 7.  It uses fairly basic CSS to style it and renders fine in HTML.

I&#39;m now after a way of converting it to PDF.  I have tried:

  - [DOMPDF][1]: it had huge problems with tables.  I factored out my large nested tables and it helped (before it was just consuming up to 128M of memory then dying--thats my limit on memory in php.ini) but it makes a complete mess of tables and doesn&#39;t seem to get images.  The tables were just basic stuff with some border styles to add some lines at various points;
  - [HTML2PDF and HTML2PS][2]: I actually had better luck with this.  It rendered some of the images (all the images are Google Chart URLs) and the table formatting was much better but it seemed to have some complexity problem I haven&#39;t figured out yet and kept dying with unknown node_type() errors.  Not sure where to go from here; and
  - [Htmldoc][3]: this seems to work fine on basic HTML but has almost no support for CSS whatsoever so you have to do everything in HTML (I didn&#39;t realize it was still 2001 in Htmldoc-land...) so it&#39;s useless to me.

I tried a Windows app called Html2Pdf Pilot that actually did a pretty decent job but I need something that at a minimum runs on Linux and ideally runs on-demand via PHP on the Webserver.

What am I missing, or how can I resolve this issue?


  [1]: https://github.com/dompdf/dompdf
  [2]: https://github.com/spipu/html2pdf
  [3]: http://www.msweet.org/projects.php?Z1

How Can I add HTML And CSS Into PDF

I asked about getting iTextSharp to render a PDF from HTML and a CSS sheet before [here][1] but it seems like that may not be possible...  So I guess I will have to try something else.

Is there an open source .NET/C# library out there that can take HTML ***and*** CSS as input and render it correctly?  

I must reiterate... the library MUST be free and preferably something with a fairly liberal license.  I&#39;m working with basically no budget here.


  [1]: https://stackoverflow.com/questions/430280/render-pdf-in-itextsharp-from-html-with-css

Open Source HTML to PDF Renderer with Full CSS Support

Is there a pdf library attached/that can be attached to .NET 3.5 that allows creation of pdf files at runtime i.e opening a new pdf file, writing to it line by line, embedding images, etc and closing the pdf file all in C# code?

What I want is a set of tools and specifications which allow me to implement a customised pdf writer in C# without using Reporting Services&#39; pdf output option.

Creating pdf files at runtime in c#

What libraries, extensions etc. would be required to render a portion of a PDF document to an image file?

Most PHP PDF libraries that I have found center around creating PDF documents, but is there a simple way to render a document to an image format suitable for web use?

Our environment is a LAMP stack.

How do I convert a PDF document to a preview image in PHP?

I would like to take a multi-page pdf file and create separate pdf files per page.

I have downloaded [reportlab][1] and have browsed the documentation, but it seems aimed at pdf generation. I haven&#39;t yet seen anything about processing PDF files themselves.

Is there an easy way to do this in python?


  [1]: http://www.reportlab.org/index.html

split a multi-page pdf file into multiple pdf files with python?

I&#39;m trying to understand what the Java *java.security.Signature* class does. If I compute an SHA1 message digest, and then encrypt that digest using RSA, I get a different result to asking the *Signature* class to sign the same thing:

	// Generate new key
	KeyPair keyPair = KeyPairGenerator.getInstance(&quot;RSA&quot;).generateKeyPair();
	PrivateKey privateKey = keyPair.getPrivate();
	String plaintext = &quot;This is the message being signed&quot;;
	
	// Compute signature
	Signature instance = Signature.getInstance(&quot;SHA1withRSA&quot;);
	instance.initSign(privateKey);
	instance.update((plaintext).getBytes());
	byte[] signature = instance.sign();
	
	// Compute digest
	MessageDigest sha1 = MessageDigest.getInstance(&quot;SHA1&quot;);
	byte[] digest = sha1.digest((plaintext).getBytes());
	
	// Encrypt digest
	Cipher cipher = Cipher.getInstance(&quot;RSA&quot;);
	cipher.init(Cipher.ENCRYPT_MODE, privateKey);
	byte[] cipherText = cipher.doFinal(digest);
	
	// Display results
	System.out.println(&quot;Input data: &quot; + plaintext);
	System.out.println(&quot;Digest: &quot; + bytes2String(digest));
	System.out.println(&quot;Cipher text: &quot; + bytes2String(cipherText));
	System.out.println(&quot;Signature: &quot; + bytes2String(signature));

Results in (for example):

&gt;Input data: This is the message being signed  
&gt;Digest: 62b0a9ef15461c82766fb5bdaae9edbe4ac2e067  
&gt;Cipher text: 057dc0d2f7f54acc95d3cf5cba9f944619394711003bdd12...  
&gt;Signature: 7177c74bbbb871cc0af92e30d2808ebae146f25d3fd8ba1622...

I must have a fundamental misunderstanding of what *Signature* is doing - I&#39;ve traced through it, and it appears to be calling update on a *MessageDigest* object, with the algorithm set to SHA1 as I would expect, then getting the digest, then doing the encryption. What&#39;s making the results differ?

**EDIT:**

Leonidas made me check whether the signature scheme is supposed to do what I think it does. There are two types of signature defined in the [RFC][1]:

* [RSASSA-PKCS1-v1_5][2]
* [RSASSA-PSS][3]

The [first of these][2] (PKCS1) is the one I describe above. It uses a hash function to create a digest, and then encrypts the result with a private key.

The [second algorithm][3] uses a random salt value, and is more secure but non-deterministic. The signature produced from the code above does not change if the same key is used repeatedly, so I don&#39;t think it can be PSS.


  [1]: http://www.apps.ietf.org/rfc/rfc3447.html
  [2]: http://www.apps.ietf.org/rfc/rfc3447.html#sec-9.2
  [3]: http://www.apps.ietf.org/rfc/rfc3447.html#sec-9.1

**EDIT:**

Here&#39;s the `bytes2string` method I was using:

    private static String bytes2String(byte[] bytes) {
    	StringBuilder string = new StringBuilder();
    	for (byte b : bytes) {
    		String hexString = Integer.toHexString(0x00FF &amp; b);
    		string.append(hexString.length() == 1 ? &quot;0&quot; + hexString : hexString);
    	}
    	return string.toString();
    }

Using SHA1 and RSA with java.security.Signature vs. MessageDigest and Cipher

i&#39;ve been google&#39;ing the difference between digital signature and digital certificate (asymmetric encryption)
seems like they are the same. I would like to clarify if they are the same or not? many thanks!!!

what is the difference between digital signature and digital certificate?

When designing an API for our web app, we&#39;ll use the their subdomain as the &#39;username&#39; and generate an API key/shared secret. Firstly, is it ok to use the subdomain as the username? I don&#39;t see the benefit of generating another key.

Different APIs seem to do one of two things:

1. **Use HTTP Basic Authentication with SSL**

In every request the username is set to the subdomain and the password to the API key. Since we&#39;re using SSL then this should be safe from spoofing.

Notable APIs: **[Google Checkout][1], [Freshbooks][2], [GitHub][3], [Zendesk][4]**

2. **Create a Signature of the Request with the Shared Secret**

Normally achieved by ordering the key/value pairs and using HMAC-SHA1 with the shared secret to generate the signature. The signature is then sent with the request and verified at the other end.

Notable APIs: **[Google Checkout][5], [Amazon AWS][6]**

PS: thats no mistake, Google Checkout supports both

**Edit:** Just read that OAuth 2 is dropping signatures in favour of sending a username/password via SSL.

Any opinions from anyone on what to pick: SSL vs Signature?


  [1]: http://checkout.google.com/support/sell/bin/answer.py?hl=en&amp;answer=57519
  [2]: http://developers.freshbooks.com/
  [3]: http://develop.github.com/p/general.html
  [4]: http://www.zendesk.com/api/rest-introduction
  [5]: http://checkout.google.com/support/sell/bin/answer.py?hl=en&amp;answer=57519
  [6]: http://docs.amazonwebservices.com/AmazonS3/latest/dev/index.html?RESTAuthentication.html

Securing an API: SSL &amp; HTTP Basic Authentication vs Signature

I am trying to create a signature using the HMAC-SHA256 algorithm and this is my code.
I am using US ASCII encoding.

    final Charset asciiCs = Charset.forName(&quot;US-ASCII&quot;);
    final Mac sha256_HMAC = Mac.getInstance(&quot;HmacSHA256&quot;);
    final SecretKeySpec secret_key = new javax.crypto.spec.SecretKeySpec(asciiCs.encode(&quot;key&quot;).array(), &quot;HmacSHA256&quot;);
    sha256_HMAC.init(secret_key);
    final byte[] mac_data = sha256_HMAC.doFinal(asciiCs.encode(&quot;The quick brown fox jumps over the lazy dog&quot;).array());
    String result = &quot;&quot;;
    for (final byte element : mac_data)
    {
        result += Integer.toString((element &amp; 0xff) + 0x100, 16).substring(1);
    }
    System.out.println(&quot;Result:[&quot; + result + &quot;]&quot;);

The result that I am getting from the above code is:

    f7bc83f430538424b13298e6aa6fb143ef4d59a14946175997479dbc2d1a3cd8

This is same as to that of shown in the wiki

    HMAC_SHA256(&quot;key&quot;, &quot;The quick brown fox jumps over the lazy dog&quot;) = 0x f7bc83f430538424b13298e6aa6fb143ef4d59a14946175997479dbc2d1a3cd8

_except_ for the `0x`.

I am looking for ideas/comments if I am doing everything right or may be I can improve my code.

HMAC-SHA256 Algorithm for signature calculation

I have an app which is signed and several keystore files. I&#39;d like to update the app, so I need to find out which one of keys was used.

How can I match which keystore was used to originally sign my app against various keystores I have on my machine?

Content Type	Original Author	Original Content on Stackoverflow
Question	Sergio	View Question on Stackoverflow
Solution 1 - C#	Darin Dimitrov	View Answer on Stackoverflow
Solution 2 - C#	Eugene Mayevski 'Callback	View Answer on Stackoverflow
Solution 3 - C#	AffineMesh	View Answer on Stackoverflow
Solution 4 - C#	user337658	View Answer on Stackoverflow

Digitally sign PDF files

C# Problem Overview

C# Solutions

Solution 1 - C#

Solution 2 - C#

Solution 3 - C#

Solution 4 - C#

How to set a breakpoint in Eclipse in a third party library?

Finding DOM node index

Attributions