Should DidiSoft OpenPGP Library for .NET provide strong name assemblies or unsigned assemblies?

Last week we have sent a short survey to subscribers for our OpenPGP Library for .NET mailing list. The survey had only one question:

Should DidiSoft OpenPGP Library for .NET provide strong name (signed) assemblies (DLL’s) or plain unsigned assemblies?

At the end of this post you will find the results of the survey, but first lets explain why did we made it.

DidiSoft OpenPGP Library for .NET was providing limited PGP emails support due to limitations in the System.Net.Mail namespace implementation regarding the MIME email formats (in fact we supported only PGP-inline emails). Recently we had received a numerous requests for additional support for PGP/MIME email format. In order to implement it we decided to use the open source MimeKit library but this is the moment where we were hit with this case:

+-------+        +---+         +--------+
|   B   +------->+ A +<--------+    D   |
+---+---+        +---+         +--------+
^                               ^
|                               |
|                               |
+---+---+                       +---+---+
|  C.1  |                       |  C.2  |
+-------+                       +-------+

Assembly A needs to use assemblies B and D, which reference different versions of assembly C. Of course this can be resolved with binding redirect in the app.config or dynamically in the AppDomain.CurrentDomain.AssemblyResolve event. But our aim was to provide a DidiSoft.Pgp.Mail.dll which use will be as simple as just referencing it straight away.

Digging for more information in Stackoverflow and MSDN we found out that probably the days when strong named assemblies were a must may have passed away. In order to hear what our community thinks we decided to file the survey. And here are the results:

The results are self explanatory – we must provide both strong named DLLs and unsigned too.

 

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OpenPGP Library for .NET 1.7.14 with Web of Trust

DidiSoft OpenPGP Library for .NET 1.7.14 was released today offering extended support for OpenPGP Web of Trust.

In previous versions of the library only setting own trust was available and plain signing of keys.

With this new release keys status can be checked by Trust amount and Verified status. We can also sign public keys with plain and trust signatures, with the option for specifying trust depth.

Check the online Tutorial for Web of Trust in order to learn this new functionality.

Upgrade notes

With this version of the library newly generated keys have Trust value of Ultimate automatically. Unfortunately if we have key pairs generated with previous versions of the library, they have Trust value Unknown. We can upgrade them with a one time execution of the code below:

C#

// ks1 is of type DidiSoft.Pgp.KeyStore
foreach (KeyPairInformation k in ks1.GetKeys())
{
      if (key.HasPrivateKey)
      {
            ks1.SetTrust(k.KeyIdHex, TrustLevel.Ultimate);
      }
}

VB.NET

' ks1 is of type DidiSoft.Pgp.KeyStore
For Each k As KeyPairInformation In ks1.GetKeys()
  If key.HasPrivateKey Then
    ks1.SetTrust(k.KeyIdHex, TrustLevel.Ultimate)
  End If
Next

 

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OpenPGP Library for .NET in Mono

DidiSoft OpenPGP Library for .NET can be used without any problems in Mono projects under Mac OSX and Linux.

The library DLL files that you have to reference in your Mono project are the ones located in the root of the \Bin folder.

A limitation for Mono developers is that they have to first install the library setup on a Windows machine in order to get the DLL files and then copy them on their Mac OSX or Linux development station.

 

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Using a public key by mistake when decrypting

A common scenario that we have evidenced in our technical support practice for DidiSoft OpenPGP Library for .NET is that some customers by mistake try to decrypt .pgp files with an OpenPGP public key.

Although the exception was of class DidiSoft.Pgp.Exceptions.WrongPrivateKeyException,  the exception text so far wasn’t very helpful and it stated: “Decryption of data encrypted using KEY-ID(s) : XXX failed, The provided key is not a valid OpenPGP private key.”.

As of version 1.7.11.11 the library was updated to check if the supplied key is a public key and in that case the exception will be “Decryption of data encrypted using KEY-ID(s) : XXX failed, The provided key is a Public Key (You need a Private Key for decryption!)

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Invoking OpenPGP Library for .NET from MS SQL Server

In this article we are going to illustrate how to invoke DidiSoft OpenPGP Library for .NET from MS SQL Server (tm) stored procedures and T-SQL code.

We also provide a dedicated set of Transact-SQL routines in the product MsSqlPGP.

Note: This information applies to MS SQL Server 2005 and above. All the demonstrated code below should be executed from SQL Server Management Studio ™ or similar environment, if not specified otherwise.

Table of Contents

Database configuration

In order to allow execution of .NET CLR code in a database, a special setting has to be activated for it:

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sp_configure 'clr enabled', 1;
GO
RECONFIGURE;

The database must allow unsafe code:

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ALTER DATABASE MyDatabase SET TRUSTWORTHY ON;

Assembly registration

The next step is to register the DLL files of the library:

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CREATE ASSEMBLY [BouncyCastle.CryptoExt]
FROM 'C:\Program Files (x86)\OpenPGP Library for .NET 1.7.10\Bin\BouncyCastle.CryptoExt.dll'
WITH PERMISSION_SET = UNSAFE;
 
CREATE ASSEMBLY [DidiSoft.Pgp]
FROM 'C:\Program Files (x86)\OpenPGP Library for .NET 1.7.10\Bin\DidiSoft.Pgp.dll'
WITH PERMISSION_SET = UNSAFE;

Wrapping the OpenPGP functionality in Stored procedures

In order to use the functionality provided by the library, we have to create wrappers as managed Stored procedures. Below is an example that exposes the basic encryption and decryption methods offered by the library:

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using System;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;
 
using DidiSoft.Pgp;
 
namespace MyStoredProcedures
{
    public partial class MsSqlPgp
    {
        [SqlProcedure()]
        public static void EncryptFile(SqlString data, SqlString publicKey, SqlString outFile)
        {
            PGPLib pgp = new PGPLib();
            pgp.EncryptFile(data.Value, publicKey.Value, outFile.Value);
        }
 
        [SqlProcedure()]
        public static void DecryptFile(SqlString data, 
                                       SqlString privateKey, 
                                       SqlString keyPassword, 
                                       SqlString outFile)
        {
            PGPLib pgp = new PGPLib();
            pgp.DecryptFile(data.Value, privateKey.Value, keyPassword.Value, outFile.Value);
        }
    }
}

Of course, the assembly where the above code resides must also be registered in the same database. Let’s assume that it is registered with the alias MyStoredProcedures. Each of its methods must be registered as a stored procedure:

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CREATE PROCEDURE usp_PgpEncryptFile
@dataFile nvarchar(MAX),
@publicKey nvarchar(MAX),
@OUTFILE nvarchar(MAX)
AS EXTERNAL NAME [MyStoredProcedures].[MyStoredProcedures].EncryptFile;
 
CREATE PROCEDURE usp_PgpDecryptFile
@pgpFile nvarchar(MAX),
@privateKey nvarchar(MAX),
@keyPassword nvarchar(MAX),
@OUTFILE nvarchar(MAX)
AS EXTERNAL NAME [MyStoredProcedures].[MyStoredProcedures.MsSqlPgp].DecryptFile;

Invoking the wrapped Stored procedures

The invocation of the wrapped code is no different than any other stored procedure call:

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EXEC usp_PgpEncryptFile 'c:\Test\mydata.txt', 'c:\Test\public.asc', 'c:\Test\output.pgp';
 
EXEC usp_PgpDecryptFile 'c:\Test\input.pgp', 'c:\Test\private.asc', 'my password', 'c:\Test\output.txt';

Upgrading the library

In order to upgrade the library to a newer version we have to first DROP any linked stored procedure, and afterwards DROP the assemblies, but in reverse order:

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DROP ASSEMBLY [DidiSoft.Pgp];
DROP ASSEMBLY [BouncyCastle.CryptoExt];

After that we shall proceed as the normal setup.

Summary

This chapter illustrated how to invoke functionality from DidiSoft OpenPGP Library for .NET in MS SQL Server ™ hosted environment.

If you need a complete solution with Transact-SQL OpenPGP cryptography, check our dedicated product MsSqlPGP.

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premature end of stream in PartialInputStream

The latest release of DidiSoft OpenPGP Library for .NET (1.7.9.14) and OpenPGP Library for Java (2.6.6.3) ship with bug fix for the error “premature end of stream in PartialInputStream“.

The error “premature end of stream in PartialInputStream” may be observed when trying to decrypt .pgp data with wrong internal length indicators , usually when the encrypted content is text data. Example of such data can be found at http://bouncy-castle.1462172.n4.nabble.com/potential-bug-premature-end-of-stream-exception-in-pgp-message-td4302017.html

In order to avoid this error, please make sure that you are using the latest version of the libraries.

The DidiSoft Team.

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Using OpenPGP for .NET from Windows PowerShell

As of version 1.7.15 we provide a PowerShell ready module installed and imported in Windows PowerShell with the library. A complete tutorial chapter is available here.

 

(Obsolete: see www.didisoft.com/net-openpgp/examples/powershell/)
This article contains basic information regarding using DidiSoft OpenPGP Library for .NET from Windows PowerShell.

1. Referencing the library

In order to access the classes exposed by the library in PowerShell we need to introduce them to the PowerShell environment. This is achieved with the Add-Type -Path command.

PS C:\Users\Me> Add-Type -Path 'C:\Program Files (x86)\OpenPGP Library for .NET 1.7.7\Bin\BouncyCastle.CryptoExt.dll'
PS C:\Users\Me> Add-Type -Path 'C:\Program Files (x86)\OpenPGP Library for .NET 1.7.7\Bin\DidiSoft.Pgp.dll'

2. Invoking methods

The method invocation is analogous to the invocation of the built-in .NET classes. Below is an example that shows how to OpenPGP encrypt a string message. Of course the library must have been referenced previously.

PS C:\Users\Me> $pgp = New-Object DidiSoft.Pgp.PGPLib
PS C:\Users\Me> $pgp.EncryptString("Hello World", "c:\OpenPGPKeys\public_key.asc")

The result from the above commands will be the encrypted string in ASCII armored format.

Summary

This chapter is just an introduction how to use DidiSoft OpenPGP Library for .NET in Windows PowerShell.

You may also be interested in examining the PowerShell module provided by the library.

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What’s the difference between Elliptic Curve OpenPGP keys and AES-256

With the new extension of the OpenPGP Standard that provides support for Elliptic Curve OpenPGP keys we have received a question from one of our customers asking what is the difference between AES-256 and the new ECC OpenPGP keys?

Short answer

The short answer is that the Elliptic Curve cryptography (ECC) OpenPGP keys are asymmetric keys (public and private key) whereas AES-256 works with a symmetric cipher (key).

Long explanation

The long answer is that the new Elliptic Curve cryptography (ECC) OpenPGP keys are designed to replace the existing asymmetric OpenPGP keys which are based on the RSA (both encryption and signing) and Diffie-Hellman (DH) (used for obtaining shared secret) and DSA (used for signature generation).

The ECC keys on the other hand use Elliptic Curve Diffie-Hellman (ECDH) shared secret protocol for encryption and Elliptic Curve Digital Signature Algorithm (ECDSA) for signature generation. An ECC OpenPGP key consists of a master key which is a ECDSA key and a sub key which is a ECDH key and is signed by the master key.

The role of the ECC OpenPGP keys is to encrypt a shared secret known as session key (as each time it is different).

AES-256 as a symmetric cipher is used to actually encrypt the data using the mentioned above session key.

The main reason that the data is not encrypted with the ECDH algorithm is that asymmetric encryption algorithms are much more slower than symmetric ones.

Summary

A common confusion is to compare asymmetric encryption algorithms and symmetric ones. In this chapter we have mentioned the new ECC OpenPG keys and the AES-256 algorithm.

You can also check the chapters describing how to specify explicitly the preferred symmetric encryption algorithm with DidiSoft OpenPGP Library:

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WPF and Silverlight support

Windows Presentation Framework (WPF)

DidiSoft OpenPGP Library for .NET works without problems in WPF (Windows Presentation Framework) applications.

The Library DLL files that you should reference are located under the /Bin folder located in the library installation folder.

Silverlight

For Silverlight applications you have to reference the DLL files located under the /Bin/Silverlight folder located in the library installation folder.

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64 bit support

DidiSoft OpenPGP Library for .NET is written completely in managed code and it runs with no modification on 32 bit and 64 bit platforms including Itanium.

The library Intermediate language (IL) code is compiled to native code by the Microsoft .NET Framework JIT (Just in time) compiler at runtime. It will run as 64-bit on a 64-bit machine and 32-bit on a 32-bit machine. The generated native code is optimized for the platform it is running on.

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