Encryption - Decrypted File Is Larger Than Source File?
Jun 15, 2012
ive been trying to use System.Security.Cryptography to encrypt and decrypt a file but its not working for me
this code
Private Sub EncryptFile(ByVal sInputFilename As String, ByVal sOutputFilename As String, ByVal sKey As String)
Dim fsInput As New FileStream(sInputFilename, FileMode.Open, FileAccess.Read)
Dim fsEncrypted As New FileStream(sOutputFilename, FileMode.Create, FileAccess.Write)
Dim DES As New DESCryptoServiceProvider()
I am writing a program to calculate Pi to several hundred billion decimal places and this will require lots of GB of memory. I wrote a test program in VB2008 that saved the first 16 digits of Pi (without the decimal point) to both a text file and a random access file, just to be sure it was outputting the numbers properly. For reference the first 16 digits of Pi are:
I am trying to decrypt a file and the decrypted contents will be loaded to a listbox.
Public Sub Decrypt(ByVal inName As String, ByVal outName As String) Try Dim array As Byte() = New Byte(&H1001 - 1) {} Dim num2 As Long = 8 Dim stream2 As New FileStream(inName, FileMode.Open, FileAccess.Read)
I am building a program that strips out certain keywords from a much larger file. I am using code that .paul. provided in a different post, but I can't get it to work correctly. Here is the code that I am using: [code] Basically, the first match will appear in textbox2, but no other matches appear after that. I put a breakpoint at the For Each loop and checked out the locals. I am showing 2,502 matches for the variable "match." I just now put another breakpoint in there and I can see that it is stepping, but nothing is recorded.In the archive is a file named debout.txt. This file should be used for the testing.
I don't know what this is called so I've struggled to find an answer from google but I have a vague memory of it from t'old days.I've sub-classed (* see below) about 8 framework controls, overriden some properties and added some functionality into each one.The changes I have made are identical in every case. If I make a change, I have to go through each class and apply the same change there.I was hoping there may be a keyword such as <IncludeSourcefile "common.vb> that I can put into each class.
(* note) I use the term sub-classed but I don't know if that's the correct terminology. I've also seen it used for call-backs. Is sub-classed the correct term to use?
I would like to read the contents of an existing Outlook 2007 PST file by VB.Net. I find already the file and record structure, this is not a problem. But I have a problem with the compressible encryption how is used. Now I have read that this encryption is based on a simple byte-substitution cipher with a fixed substitution table. But unfortunately I can't find this table. Maybe someone can help me where to find this table or where I to find all the necessary information about compressible encryption.
Imports System Imports System.IO Imports System.Security Imports System.Security.Cryptography
[code]....
The above code is used by me to encrypt .avi files and it worked very well but the problem is that if the size of my video file is greater than 200 mb memory overflows probably as the code copy the whole input file into ram and then process it hence it put limitation of hardware,is there any better way to do it so that files > 200 mb could me encrypted in PCs with 1gb ram?
In my program I allow the user to copy a file from one folder to another. If the file already exists in the target folder I want it to be overwritten.
All that works just fine - I'm not asking how to copy files.
But here's an example
Source file is:-
\SomeMachinesomeFolderfile.xyz
Target is:-
P:file.xyz
This might at first look like two separate files but in this case P: is mapped to \SomeMachinesomeFolder so the source and the target are actually the same file and the file copy will obviously fail.
Of course I want it to fail but my problem is that the windows generic error message seen by the user is not very helpful. It says something simple like "... can't be copied because it's busy". If the user isn't very bright he doesn't realize he's selected the same file both as source and target and he doesn't understand why it's busy.
What I want to do is detect in advance that the source and the target are the same file and display a more meaningful message to the user and not even bother trying to copy.
I'm looking for advice/ideas in regards to ongoing file encryption.I have an event that fires frequently that contains small amounts of data passed through the eventargs.This data is then written out to disk (currently unencrypted).I need to encrypt this data (which, I can do).My attempt in the first five minutes was unencrypting the file, appending the data and reencrypting the file.This obviously works, but is pretty inefficient and not going to be my solution since the file could grow rather large and the resources to unecrypt/ encrypt grow larger as the file grows larger.My next thought was to encrypt each set of data as it's written out and have some kind of marker in the file to denote where to split so I could unencrypt each chunk to reproduce the original file.I'm leaning towards this approach now (though by encrypting small chunks of data multiple times, the file size will be considerably larger.As an example, if I encrypt each letter of the alphabet the file is approx 8 times larger than if I encrypted a string with all of the letters of the alphabet in this case each files decrypted content would be identitcal).
1. How much load or data size our custom encryption/decryption algorithm can handle? E.g. what's the limit of file size that normal encryption/decryption algorithm supports.
2. What's the best way to use encryption while file transfer via internet?
3. Where and when encryption and decryption has to apply while uploading and downloading content from internet(Hosting on client or server machines)?
4. What type of algorithms suites for above approaches?
5. How much time it takes to encrypt / decrypt data for 10 MB, 100 MB, 1 GB etc
I am trying to make a key that will be used in file encryption/decryption for my application. However, there is no user data involved with this application (As i would usually use the user's password to generate the encryption key), so i have to turn to another method.
I am thinking that maybe it is possible to generate a completely random key the first time the program runs, then save this key inside the program so that it is inaccessible by the user. The user will not be shown this key, but the key MUST be randomly generated for each application, and it also must stay constant once it is created.
I use the following Rijndael code to do encryption without fail for many times. But why it can not encrypt an ISO file with 4.2 GB? In fact my computer has 16GB memory and it should not be a memory problem. I use Windows 7 Ultimate. The code is compiled as winform (.Net 4) using Visual Studio 2010 (a VB.NET project).
I have checked that the ISO file is OK and can be mounted as virtual drive and even can be burnt to DVD rom. So it is not the ISO file problem.My question: Why the following code cannot encrypt an ISO file with size of 4.2GB? Is that caused by the limitation of Windows/.NET 4 implementation?
What I've decided to start working on is pretty much a personal project but something I may use in my UNI course in due time. I'm creating a security program with a set of access codes (yes I am a bit of a star trek fan) - 4 in total to be exact. I want to be able to use an Encrypted key file in form of a simple notepad created text file to update the codes at any due time. All I'm looking to do is write the access codes to the text file (say for a friend to use the program), Encrypt the file through the program and be able to also decrypt to obtain the new access codes on demand also via the same program. Once decrypted the codes can be read and verified if the user has entered each one correctly. I could hard code the access codes into the program but would rather do it the way I've thought of.
Back in the days of the old VB6 there was a simple method but for some reason that doesnt work any more. What I guess I'm looking to do is have 4 text fields where 4 digit access codes are typed into, have the program take them and encrypt each one is then written to the text file. Hoping that will make it a bit clearer what I'm trying to achieve as I think I made it sound like I want to encrypt the text file after the info has been written to it, which is of course one option so wouldn't mind know how to do that too!
I'm working on a basic file encryption by using the Imports System.Security.Cryptography.I was thinking of putting a password as a final security measure.Would i have to store the password inside the file or how will this work?
I recently changed application settings to be in an encrypted config file.The first time I run any application and try to retrieve a setting (My.settings. ...) from the config file I get an Unrecognized attribute 'configProtectionProvider'If I restart the application I don't get an error due to the fact that it doesn't re-encrypt during that run. Why when I run the application for the first time am I getting this error?
I am encrypting the config file on application startup using the following code:
I recently made a simple pseudo-encryption program that changes each character into another. It is capable of encrypting and decrypting a string. This can also be done to any text file as well. The characters range from ASCII 32-254 (This on it's own may be an issue because of #127 being DEL).
Because I believed my own coding may be at fault, I attempted this with Triple Des with identical results.For Triple Des, the requirements for en/decryption was:
Encrypt: String to Byte Decrypt: Byte to String
And to change them either direction, I used UTF8. I also attempted ASCII and UTF32, but I don't know what I should do. I am considering dropping this but I want to learn problems like this because I am currently in college and haven't started my core classes for programming yet and want the head start.
The point where I have come into a problem is attempting to do this to another file type like an image. I looked at the results from encrypting then decrypting and the results were similar, but it seems file encoding must be the culprit.
I just tried debugging my game using the green play button, what ever thats called, and upon telling the debugger to break on a few lines, each time it actually hit that respective line, I got an error from vs2010 telling me that the source files were different than they were when the program was compiled...and every time that I USED to change the files, and then debug the program, vs2010 would automatically rebuild the files...
Is it possible to see the source code through the program debug database file. I lost the source code file but eventually I just have the exe and the pdb file, I am just wondering is there a possibility to get the source code through the pdb ?
This should be very simple but I'm very new to Visual Studio so I can't get it to work. I want to take data from an excel (2003) file and turn it into a bunch of charts that would be viewable on a webpage that I'm trying to build in Visual Studio .Net 2005 professional.
I can't seem to use an excel file as my data source, here are the steps that I've followed:
1) created a new asp.net project
2) dragged a report viewer from the toolbox and it asks me to choose a report or "Design New Report."
3) Clicked Design New Report, and it opened up a new blank report.
4) Clicked "Add New Data Source" and got the Table Adapter Configuration Wizard.
5) Clicked new connection and it brought up the Add connection table.
6) Clicked "change" under data source and I chose Microsoft ODBC Data Source (not sure if that's right.)
7) Under "Data source specification" I chose "Excel Files"
- The first time I did this it brought up a window for me to choose an excel file so I did. Something along the way failed out but it stilled saved "ConnectionString1" as a connection to that first excel file. Now every time after I choose "Excel Files" and click "OK" the add connection window disappears and it goes back to the Table Adapter Configuration Wizard with the "ConnectionString1" as the connection string. It won't let me specify any different excel file. So I did 1-6 again and picked up at 7B
7B) Instead of using "Use user or system data source name:" I chose "Use connection string:" and clicked Build.
8) Picked the "Machine Data Source" tab and chose "Excel Files" and clicked ok
9) The "Select Workbook" window appears so I went to the file I wanted to use as my data source and click OK
10) Back on the Add Connection window I clicked test connection and it succeeded so I clicked ok.
11) It goes back to the Table Adapter Config Wiz window, but the connection string only says "Dsn=Excel Files"
12) clicked Next, then Next again, then clicked on Query Builder. The Add Table window pops up but there is nothing in there for me to choose from.I've tried a million other things, here are a few of the errors that I seem to get a lot.
[IM006][Microsoft][ODBC Driver Manager] Driver's SQLSetConnectAttr failed [HYC00][Microsoft][ODBC Excel Driver] Optional feature not implemented [HY001][Microsoft][ODBC Excel Driver] Too many fields defined.
Does anyone have any thoughts? Is there a reference I need to add or something?
I'm writing a .txt file which is loaded using the following code. When running a Debug I get a message on closing the .txt file saying 'This file has been modified outside the source editor. Do you want to reload it?' Is this juszt a nag screen for the editor, or will I get an error from the final compiled .exe program build?
I want to get two sets of information from a source file. Say user name and address to their profile. I so far I'm using two for next loops to get the information I want and save it into the text file. Works great. Problem: I would like to print to file first line of For Next output then append to that the first output of the second For Next loop. Then do the same for second out put until the end of each For Next loop is complete. [Code]
I am trying to extract inforamtion from a website, I was able to get to the point of extract HTML to TXT. not I want to parse from this line TOTAL 3723
I have "added an existing project" to my solution. This item has been used in several different solutions but I am running into an issue for the 1st time w/ it.
I have 2 applications:
X & Y
I copied the "existing project" from the X folder to the Y folder (so I would not be altering the same "existing project". Then I "added" the project from the new Y location. I also added reference to the DLL file in location Y. However when I debug from program Y it keeps running the code from location X. Everything that I know to look at looks correct. Any ideas on what is causing the issue and how to resolve it?
FYI, To prove the point I changed the folder name for testing in the X folder. When I then debug program Y i get this error:
