The path parameter is null. The file described by the path parameter could not be found. The path parameter specified a file that is read-only. The following code example uses the Encrypt method and the Decrypt method to encrypt and then decrypt a file.
The file must exist for the example to work. The Encrypt method allows you to encrypt a file so that only the account used to call this method can decrypt it. Use the Decrypt method to decrypt a file encrypted by the Encrypt method. Use of this API in. NET Core is not recommended; it is included to enable portability for applications that move to. NET Core but still explicitly target Windows.
The Encrypt method requires exclusive access to the file being encrypted, and will fail if another process is using the file. Before we write the event handler however, we will create a function to clear down the program's variables and reset the interface to its original state.
Private Sub Clear txtMessage. ControlLight cmdSave. Not too much in the way of explanation should be needed for this bit of code. It clears the contents of both text boxes, clears the character array chrCodeKeyArray , and sets the program's display back to its original state. The procedure is defined separately rather than within the Cancel button's Click event handler because we will also be calling it from another part of the program.
The local character variable EncodedChar holds the result of the character encoding algorithm. The If. Otherwise, the function generates random replacement characters until it finds one that has not already been used this is achieved using a Do. Loop Until construct whose exit condition is that the randomly generated character is not already in the array.
Once it has achieved this goal, the successful candidate is stored in the appropriate location within the array and a copy of the value is returned by the function. Text - 1 If Asc txtMessage. Text i End If Next txtEncoded. The string variable strTemp declared in the first line is used to store the output from the encryption algorithm and build the encoded message. The code loops through the text message one character at a time, calling the Encode function to encode each character.
If the character entered by the user is for whatever reason not one of the printable characters found in the basic ASCII character set, then a space character is encoded in its place. Once the input string has been encoded, the event handler assigns the encoded string to the Text property of the application's second text box txtEncoded.
It then disables the Encrypt button, sets the ReadOnly property of the input text box to True , and sets the BackColor property of the input text box back to its initial colour to draw the user's attention to the fact that the input box is currently disabled once more. The last line in the event handler code enables the Save to File button so that the user can save the encypted message if they wish to the only other option at this stage being to cancel the whole operation.
The code for saving the encrypted message is relatively straightforward, and uses the services of the SaveFileDialog control sfdEncFile. OK Then My. WriteAllText sfdEncFile. FileName, txtEncoded. FileName, 1, Len sfdEncFile. The first line of code here sets the SaveFileDialog control's filter so that files are saved with the. If the user has entered a filename and clicked OK , the rest of the code defined within the If. End If block will execute. The first line in this block simply writes the encoded message to the file designated by the user if the file already exists, any existing contents are over written.
The next line uses the string variable strKeyFileName to create the filename for the encryption key file. It does this by stripping off the file extension from the encrypted message's filename, and adding a new file extension.
The character array chrCodeKeyArray is then written into a second file with this new filename. This process will occur transparently from the user's point of view, although they will obviously be able to see the.
Learn more. Asked 4 years, 4 months ago. Active 4 years, 4 months ago. Viewed times. Read plainTextBytes, 0, plainTextBytes. Length memoryStream. Close cryptoStream. Close The problem that I am having is that I don't know how to read a. Why would you want to encrypt the data one line at a time? Line breaks in text are just characters like any other. When you encrypt text you convert the entire text to bytes and then you encrypt those bytes. When you decrypt, you decrypt all the data and then you convert the resultant bytes into text.
Add a comment. Active Oldest Votes. Darin Dimitrov Darin Dimitrov k gold badges silver badges bronze badges.
0コメント