Re: Encryption and decryption - C# Discussion Boards

OriginalGriff8-Mar-12 20:20

8-Mar-12 20:20

The Key is the actual data that will be used to encrypt or decrypt the whole message. Think of it as the "Password" to the message.
The IV is a set of random numbers used as a "salt" to start the encryption process.

If all your messages start the same way, then if you know the start of one message, it is easier for you to work out the key for a different message - because you know some of the data that made it up. The IV prevents that happening by providing a set of random numbers to start the encryption process, which vary from message to message. That is why they are transmitted in clear, normally as a block of bytes at the front of the message. Knowing the IV values gives you nothing if you are trying to hack the message - it is normally XORed with the first block of data before encryption so it becomes less readable. Subsequent blocks of data use the output from the first block to generate the IV for the second, and so forth.
If you are feeling particularly paranoid, then just prefix your actual data with a block full of random rubbish, so that by the time the encryptor gets to any duplicated data it has already mangled the IV to death... Laugh | :laugh:

Ideological Purity is no substitute for being able to stick your thumb down a pipe to stop the water

sandy_419-Mar-12 0:12

sandy_41

9-Mar-12 0:12

Thanx for your explination and can i know where this information is available (like text books...)

Because i want to know that in detail.

OriginalGriff9-Mar-12 0:25

9-Mar-12 0:25

Sorry, but I can't help you there!
It's been so long since I learnt this stuff that I have no chance of remembering which text books I used... Laugh | :laugh:

The best guess I can offer is that it is accrued from a multitude of textbooks, plus the internet, plus experience! Not very helpful, I know... Big Grin | :-D

Ideological Purity is no substitute for being able to stick your thumb down a pipe to stop the water

sandy_419-Mar-12 0:27

sandy_41

9-Mar-12 0:27

not an issue Smile | :)

Matt Meyer9-Mar-12 3:54

Matt Meyer

9-Mar-12 3:54

Schneier's stuff is generally regarded as the best around.

Applied Cryptography (https://www.schneier.com/book-applied.html[^]) is probably the best you're going to find on the subject. The book itself is a little dated, but it's still a very, very good reference, and the majority of the topics are still relevant today. It's a very technical, and requires a working knowledge of C and some advanced mathematics.

He's got some other less technical books as well on the subject of cryptography - Practical Cryptography is decent if you don't want to know the inner workings, but want to know how to effectively select correct algorithms and implement cryptography.

I haven't read Cryptography Engineering yet, it's supposed to be a second edition of Practical Cryptography. I'm not sure if it gets as technically detailed as Applied.

A list of his books are at https://www.schneier.com/books.html[^]

Wayne Gaylard9-Mar-12 0:36

Wayne Gaylard

9-Mar-12 0:36

Nice explanation! Big Grin | :-D

When I was a coder, we worked on algorithms. Today, we memorize APIs for countless libraries — those libraries have the algorithms - Eric Allman

OriginalGriff9-Mar-12 0:40

Where is this c# console application running from??

9-Mar-12 0:40

Thank you!

Ideological Purity is no substitute for being able to stick your thumb down a pipe to stop the water

Goalie358-Mar-12 17:08

Goalie35

8-Mar-12 17:08

Our client has a windows 2003 server, which contains a c# console application, which is currently executing once a week, and I need to stop this application from running. The problem is, I don't know where the original developers of this app, scheduled it to run from.

Our client severed ties with their prior development company, so we just inherited their work from this yesterday. I've been able to locate the directory where the c# console application is located, but I can't figure out where on this windows server 2003 box, this application is running from. I've checked scheduled tasks as well as windows services, but haven't found any trace of the executable.

Any possible suggestions as to where else someone may schedule a c# console application to run on a windows server 2003 box?

Thanks.

Re: Where is this c# console application running from??

Roger Wright8-Mar-12 17:30

Roger Wright

8-Mar-12 17:30

IIRC, the AT command allows an administrator to run an app at specified times, but doesn't show up in Task Scheduler. This[^] article tells you how to create an AT command, and how to cancel one. I hope it helps.

Will Rogers never met me.

Re: Where is this c# console application running from??

RobCroll9-Mar-12 3:19

RobCroll

9-Mar-12 3:19

Also it could be another service or scheduled task that runs the console app. Why not try and delete it. That'll stop it Smile | :)

"You get that on the big jobs."

Re: Where is this c# console application running from??

Roger Wright9-Mar-12 5:02

Roger Wright

9-Mar-12 5:02

Renaming it might be safer. It's likely that an error message will result at some point, possibly narrowing the search for a starting service. If it turns out that the program is necessary for something, the old name can be easily restored.

Will Rogers never met me.

Re: Where is this c# console application running from??

jschell9-Mar-12 5:23

jschell

9-Mar-12 5:23

I think process explorer or at least one of the other sysinternals utilities (now owned by MS) allows you to track down process owners.

http://technet.microsoft.com/en-us/sysinternals/bb896653[^]

Re: Where is this c# console application running from??

Vasudevan Deepak Kumar9-Mar-12 9:54

Vasudevan Deepak Kumar

9-Mar-12 9:54

It might not help him because it runs once a week and exits after running.

Vasudevan Deepak Kumar
Personal Homepage
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Decimal format in the textbox Text Change C# (1000000 -> 1,000,000)

nhanlaptrinh8-Mar-12 16:03

Re: Decimal format in the textbox Text Change C# (1000000 -> 1,000,000)

8-Mar-12 16:03

Have you asked yourself in the currency format function TextChange how my example below the cursor does not focus on the No. 2 spot, the book help me thanks!

if (textBox1.Text == "")
return;
else
{
int iIndex = textBox1.Text.IndexOf('.');
if (iIndex == -1)
{
}
else
{
string strT = textBox1.Text.Substring(iIndex + 1, 1);
if (textBox1.Text != "")
{
}
}
double a = double.Parse(textBox1.Text.Trim(','));
textBox1.Text = a.ToString("#,###");
}

modified 8-Mar-12 22:18pm.

OriginalGriff8-Mar-12 20:37

Re: Decimal format in the textbox Text Change C# (1000000 -> 1,000,000)

8-Mar-12 20:37

Sorry, but that doesn't make much sense.
When you post code, please use the code widget above the textbox - it preserves formatting which makes the whole thing more readable.
I have reformatted your code, and also refactored it to make it more readable - taking out redundant conditions and so forth:

if (textBox1.Text != "")
    {
    int iIndex = textBox1.Text.IndexOf('.');
    if (iIndex != -1)
        {
        string strT = textBox1.Text.Substring(iIndex + 1, 1);
        }
    double a = double.Parse(textBox1.Text.Trim(','));
    textBox1.Text = a.ToString("#,###");
    }

The trouble is that I have no idea what you are trying to do, so I also have no idea what problem you are trying to get help with!
Please try to explain a bit better so we can help you.

Ideological Purity is no substitute for being able to stick your thumb down a pipe to stop the water

nhanlaptrinh9-Mar-12 0:56

Re: Decimal format in the textbox Text Change C# (1000000 -> 1,000,000)

9-Mar-12 0:56

We now want to enter the number into the textbox, textbox itself decimal format and displays the time on that textbox. For example, enter "123456789", the textbox will appear as 123,456,789. I have a problem when entering a string from 1 to 9 are ok, but when inserting a number in the range from 1 to 9, the textbox back to position the cursor on the first position, thanks to your help with , thank you very much.

Code I wrote

private void textBox1_TextChanged(object sender, EventArgs e)
        {
            try
            {
                if (textBox1.Text != "")
                {
                    int iIndex = textBox1.Text.IndexOf('.');
                    if (iIndex != -1)
                    {
                        string strT = textBox1.Text.Substring(iIndex + 1, 1);
                    }
                    double a = double.Parse(textBox1.Text.Trim(','));
                    if (textBox1.SelectionStart >= textBox1.Text.Length)
                    {
                        textBox1.Text = a.ToString("#,###");
                        textBox1.SelectionStart = textBox1.Text.Length;
                    }
                    else
                    {
                        textBox1.Text = a.ToString("#,###"); 
                        //Help?
                    }
                }
            }
            catch (Exception) { MessageBox.Show("Must enter the number ."); }
        }

modified 9-Mar-12 7:18am.

Bernhard Hiller9-Mar-12 2:23

Bernhard Hiller

9-Mar-12 2:23

Do not use the TextChanged event, LostFocus or Validating are better.

Re: Decimal format in the textbox Text Change C# (1000000 -> 1,000,000)

nhanlaptrinh9-Mar-12 2:35

Re: Decimal format in the textbox Text Change C# (1000000 -> 1,000,000)

9-Mar-12 2:35

I think there are workarounds, but they have not thought out.

nhanlaptrinh9-Mar-12 16:49