Re: Encryption and Decryption - C# Discussion Boards

Sathesh Sakthivel8-Jun-07 2:19

Sathesh Sakthivel

8-Jun-07 2:19

The System.Security.Cryptographic namespace within the Microsoft .NET Framework provides a variety of tools to aid in encryption and decryption. The CryptoStream class is used here to demonstrate the encryption and decryption with System.Security.Cryptographic.SymmetricAlgorithm.

For Details[^]

Regards,

Satips. Rose | [Rose]

Pixinger778-Jun-07 3:10

Pixinger77

8-Jun-07 3:10

I cant help you with SHA256, but maybe another solution is acceptable for you.
I'am using the MD5, but this is only a unidirectional encryption.

I show a dialog to enter a password and encrypt the password via MD5. The encrypted result will then be stored in a database.
When the user logs on again, he must enter the password, which will be encrypted again with MD5.
To verify if the password is correct i compare the encryption stored in the database, with the new encryption.

To get the MD5 encryption do the following:

public static string StringToMd5(string text)
        {
            byte[] data = System.Text.Encoding.Unicode.GetBytes(text);
            System.Security.Cryptography.MD5 md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
            byte[] result = md5.ComputeHash(data);
            System.Text.StringBuilder s = new System.Text.StringBuilder();
            foreach (byte b in result)
            {
                s.Append(b.ToString("x2").ToLower());
            }
            return s.ToString();
        }

may be it suits you...
greets Snow

originSH8-Jun-07 3:48

originSH

8-Jun-07 3:48

Just as a note MD5 is considered insecure now and it's recommended to change to the SHA-1 hash instead.

Packing a class into a byte array - would [Serializable] do the trick?

Russell Jones8-Jun-07 4:39

Russell Jones

8-Jun-07 4:39

using System;<br />
using System.Collections.Generic;<br />
using System.Text;<br />
using System.Security.Cryptography;<br />
<br />
namespace Helper.Crypto<br />
{<br />
   public class HashMethods<br />
   {<br />
      public static string GenerateSalt()<br />
      {<br />
         //Create 32 bytes of random data for use as  a salt<br />
         byte[] Salt = new byte[32];<br />
         RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();<br />
         rng.GetNonZeroBytes(Salt);<br />
         return Encoding.UTF8.GetString(Salt);<br />
      }<br />
      public static string Hash(string text,string saltString)<br />
      {<br />
         string SaltedString = text + saltString;<br />
         byte[] SaltedText =  Encoding.UTF8.GetBytes(SaltedString);<br />
         HashAlgorithm hash = new SHA512Managed();<br />
         byte[] hashBytes = hash.ComputeHash(SaltedText);<br />
         return Convert.ToBase64String(hashBytes);<br />
      }<br />
   }<br />
}

I store both the salt and the hashed PWD+Salt in a DB.
When a client tries to log in the server gives it the salt and the client adds the salt to the username and hashes. pass the hashed password up to the server and compare with the value stored in the DB.
This way you never know the user's password.

HTH

Russ

SQL Connection DialogBox

ScottM18-Jun-07 2:07

ScottM1

8-Jun-07 2:07

Does anybody know how I can get the SQL Connection DialogBox to show up in C#?
You know, the one that comes up when you open SQL query analyzer. I think that I need to use Microsoft.Data.ConnectionUI which I need to install another SDK to use. Does anybody know which SDK this is?

Any help would be appreciated
Thanks

There are 10 types of people in the world, those who understand binary and those who dont.

Dewald8-Jun-07 2:02

Re: Packing a class into a byte array - would [Serializable] do the trick?

8-Jun-07 2:02

I'm looking for a way to represent an instantiated class as a byt array (and populate an instantiated class frm a byte array. I was hoping that [Serializable] would be the magic bullet but it seems I was wrong - or do I just not understand how to use [Serializable] properly?

Let's say I have:

public class myClass
{
   public byte myByte1;
   public byte myByte2;
   public ushort myUshort1;
   public ushort myUshort2;

   public myClass()
   {
      this.myByte1 = 0x01;
      this.myByte2 = 0x02;
      this.myUshort1 = 0x0304;
      this.myUshort2 = 0x0506;
   }
}

Now, if I instantiate this class with myClass myInstance = new myClass() the member variales will hold the values as defined by the constructor. I'd like to be able to view the contents of the class as an array of bytes (ie. {0x01, 0x02, 0x03, 0x04, 0x05, 0x06}).

So I was thinking that if the class is serializable and I write the seraialized stream to a byte array (or write a byte array to the associated stream) I'd be able to pull it off, something like this:

MemoryStream memStream = new MemoryStream();
BinaryFormatter binFormatter = new BinaryFormatter();
binFormatter.Serialize(memStream, myInstance);
byte[] myBytes = memStream.ToArray();

But myBytes is 183 bytes in size (as opposed to the expected 6 bytes) once this is finished and the contents of myBytes makes no sense to me whatsoever.

Am I on completely the wrong track here or is there hope?

AikinX8-Jun-07 2:16

Re: Packing a class into a byte array - would [Serializable] do the trick?

8-Jun-07 2:16

Here are many additional information is added with serialization like assembly name, version, class name, structure, ........
All this information is necessary to deserialize this object

Dewald8-Jun-07 2:38

Re: Packing a class into a byte array - would [Serializable] do the trick?

8-Jun-07 2:38

Aha, that makes sense. So does that mean that [Serializable] would not be the proper route then?

Would you have any other suggestions?

AikinX8-Jun-07 3:27

Re: Packing a class into a byte array - would [Serializable] do the trick?

8-Jun-07 3:27

Dewald wrote:
Aha, that makes sense. So does that mean that [Serializable] would not be the proper route then?

Yes, if the array size is not critical.
If critical you have to realize you own convertion like:

<br />
    public class myClass<br />
    {<br />
        public byte myByte1;<br />
        public byte myByte2;<br />
        public ushort myUshort1;<br />
        public ushort myUshort2;<br />
<br />
        public myClass()<br />
        {<br />
<br />
        }<br />
<br />
        public static byte[] ToByteArray(myClass value)<br />
        {<br />
            byte[] result = new byte[6];<br />
<br />
            result[0] = value.myByte1;<br />
            result[1] = value.myByte2;<br />
            unchecked<br />
            {<br />
                result[2] = (byte)(value.myUshort1 / 256);<br />
                result[3] = (byte)(value.myUshort1 - result[2] * 256);<br />
                result[4] = (byte)(value.myUshort2 / 256);<br />
                result[5] = (byte)(value.myUshort2 - result[4] * 256);<br />
            }<br />
<br />
            return result;<br />
        }<br />
<br />
        public static myClass FromByteArray(byte[] array)<br />
        {<br />
            myClass result = new myClass();<br />
<br />
            result.myByte1 = array[0];<br />
            result.myByte2 = array[1];<br />
            result.myUshort1 = (ushort)(array[2] * 256 + array[3]);<br />
            result.myUshort2 = (ushort)(array[4] * 256 + array[5]);<br />
<br />
            return result;<br />
        }<br />
    }<br />

P.S. usort is 16-bit type so we need to store it into two bytes.

Dewald8-Jun-07 3:37

Re: Packing a class into a byte array - would [Serializable] do the trick?

8-Jun-07 3:37

Yip, this is exactly what I've been doing up until now but I was just hoping that there wuld be a more elegant sollution. The thing is that I have various classes that I'd like to be able to pack into byte arrays (basically the classes are just messages that I need to transmit and receive over a TCP socket).

I was hoping that I could write a base class that provides a method of packing the class into an array and then derrive all the other classes from that class. That way I wouldn't have to implement a huge amount of tedious code to pack every individual member variable of the class into the array.

AikinX8-Jun-07 4:08

Re: Packing a class into a byte array - would [Serializable] do the trick? [modified]

8-Jun-07 4:08

Sorry, I have no ideas how to help you this case.

If you message is more than 6 byte the volume of valuable information will be more. Also you may try to zip it by DeflateStream....

AikinX8-Jun-07 20:43

Re: Packing a class into a byte array - would [Serializable] do the trick?

8-Jun-07 20:43

Dewald, last night I got an idea: in unmanaged C++ we just need to look at the object as byte array:

<br />
// Some & and * have to be added to next code to say we are working with references<br />
MyClass myCl = new MyClass();<br />
byte[] array = meCl; // this operation is allowed fo references<br />
// coping this array to new one or sending it as is through TCP socet<br />

But in .Net we haven't references (that is very good, in my opinion), but we have some classes that allow to work with objects by references way.
One of them is System.Runtime.InteropServices.Marshal

I have never worked with, just herad about it.
I have being looking through this and find some pairs of static methods wich can help you (I guess):
To get IntPTR from your object:
public static extern void StructureToPtr(object structure, IntPtr ptr, bool fDeleteOld);
public static object PtrToStructure(IntPtr ptr, Type structureType)

To copy to byte array:
public static void Copy(IntPtr source, byte[] destination, int startIndex, int length);
public static void Copy(byte[] source, int startIndex, IntPtr destination, int length)
Or
public static extern byte ReadByte(object ptr, int ofs);
public static extern void WriteByte(IntPtr ptr, int ofs, byte val);

Regards.

P.S. IntPtr (intPointer) is Net analog of C++ pointers

-- modified at 2:48 Saturday 9th June, 2007

AikinX8-Jun-07 23:50

Re: Packing a class into a byte array - would [Serializable] do the trick?

8-Jun-07 23:50

I've done the copying for value object (structure). One thing I can't make is to get a pointer (IntPtr) from reference object (class).

<br />
    public struct myStuct<br />
    {<br />
        public byte myByte1;<br />
        public byte myByte2;<br />
        public ushort myUshort1;<br />
        public ushort myUshort2;<br />
<br />
        private const int MY_SIZE = 6;<br />
        public static byte[] ToByteArray(myStuct source)<br />
        {<br />
            // Allocating an unmanagement memory for marshaling<br />
            IntPtr pointer = System.Runtime.InteropServices.Marshal.AllocHGlobal(MY_SIZE);<br />
            // Copying instance to allocated memory<br />
            System.Runtime.InteropServices.Marshal.StructureToPtr(source, pointer, false);<br />
<br />
            byte[] result = new byte[MY_SIZE];<br />
            // Coping filled memory to byte array<br />
            System.Runtime.InteropServices.Marshal.Copy(pointer, result, 0, MY_SIZE);<br />
<br />
            return result;<br />
        }<br />
<br />
        public static myStuct FromByteArray(byte[] source)<br />
        {<br />
            if (source == null) throw new ArgumentNullException("Source array can not be null");<br />
            if (source.Length != MY_SIZE) throw new ArgumentException("Source array's size has to be " + MY_SIZE + " bytes");<br />
<br />
            // Allocating an unmanagement memory for marshaling<br />
            IntPtr pointer = System.Runtime.InteropServices.Marshal.AllocHGlobal(MY_SIZE);<br />
            // Coping byte array to allocated memory<br />
            System.Runtime.InteropServices.Marshal.Copy(source, 0, pointer, MY_SIZE);<br />
<br />
            // Creating instance from unmanagment memory<br />
            myStuct result = (myStuct)System.Runtime.InteropServices.Marshal.PtrToStructure(pointer, typeof(myStuct));<br />
<br />
            return result;<br />
        }<br />
    }<br />

Dewald10-Jun-07 23:09

Re: Packing a class into a byte array - would [Serializable] do the trick?

10-Jun-07 23:09

Thanks for all the effort AikinX,

I also discovered this approach but, like you, I couldn't get it to work for classes. I never even bothered to try using it for structures (silly of me) and this will do nicely.

It is a bit of a pity that I have to resort to unmanage code. I would have prefered if there was a way that I could do this without having to use pointers, and there probably is which is still elluding me.

Either way, for now, this will do. Thanks again.

AikinX11-Jun-07 0:15