C# Signature:

    [DllImport("mscorsn.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.U1)]
    static extern bool StrongNameSignatureVerificationEx(
         [MarshalAs(UnmanagedType.LPWStr)]string wszFilePath,
         [MarshalAs(UnmanagedType.U1)]bool fForceVerification,
         [MarshalAs(UnmanagedType.U1)]ref bool pfWasVerified);

User-Defined Types:

None.

Notes:

This function is exported from mscorsn.dll in v1.0 and v1.1 of the .NET framework, but it will be moved to mscorwks.dll in v2.0. There is a shim in mscoree.dll which will redirect to the appropriate implementation dll, which has the same name.

Tips & Tricks:

The fForceVerification / pfWasVerified parameters can be confusion. A good blog entry to read, which explains how these work can be found here: http://blogs.msdn.com/shawnfa/archive/2004/06/07/150378.aspx

See the supporting function below for the code to the CheckToken() function - it verifies that an assembly contains the correct token data.

Sample Code:

// check the signature first
bool notForced = false;
bool verified = StrongNameSignatureVerificationEx(assembly, false, ref notForced);
Console.WriteLine("Verified: {0}\nForced: {1}", verified, !notForced);

// check to see if it is a Microsoft assembly
byte[] msClrToken = new byte[]    { 0xb7, 0x7a, 0x5c, 0x56, 0x19, 0x34, 0xe0, 0x89 };
byte[] msFxToken = new byte[]    { 0xb0, 0x3f, 0x5f, 0x7f, 0x11, 0xd5, 0x0a, 0x3a };
bool isMsAsm = CheckToken(assembly, msClrToken) || CheckToken(assembly, msFxToken);

if(isMsAsm && verified && notForced)
    Console.WriteLine("Microsoft signed assembly");
else if(isMsAsm && verified && !notForced)
    Console.WriteLine("Microsoft delay signed assembly");
else if(isMsAsm && !verified)
    Console.WriteLine("Microsoft assembly, modified since signing");
else
    Console.WriteLine("Not a Microsoft assembly");

Supporting Function:

    /// <summary>
    /// Check an assembly to see if it has the given public key token
    /// </summary>
    /// <remarks>
    /// Does not check to make sure the assembly's signature is valid.
    /// Loads the assembly in the LoadFrom context.
    /// </remarks>
    /// <param name='assembly'>Path to the assembly to check</param>
    /// <param name='expectedToken'>Token to search for</param>
    /// <exception cref='System.ArgumentNullException'>If assembly or expectedToken are null</exception>
    /// <returns>true if the assembly was signed with a key that has this token, false otherwise</returns>
    public static bool CheckToken(string assembly, byte[] expectedToken)
    {
        if (assembly == null)
        throw new ArgumentNullException("assembly");
        if (expectedToken == null)
        throw new ArgumentNullException("expectedToken");

        try
        {
        // Get the public key token of the given assembly
        Assembly asm = Assembly.LoadFrom(assembly);
        byte[] asmToken = asm.GetName().GetPublicKeyToken();

        // Compare it to the given token
        if (asmToken.Length != expectedToken.Length)
            return false;

        for (int i = 0; i < asmToken.Length; i++)
            if (asmToken[i] != expectedToken[i])
            return false;

        return true;
        }
        catch (System.IO.FileNotFoundException)
        {
        // couldn't find the assembly
        return false;
        }
        catch (BadImageFormatException)
        {
        // the given file couldn't get through the loader
        return false;
        }
    }

Alternative Managed API:

None