Encrypting and Decrypting RTF files?
Question
Answers
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Jason,
Food for thought here. You only want it to be able to be "read" from your program and you also want that if someone opens the file in a text reader (like NotePad), it will show gibberish.
Here's what I set up - a form with a RichTextBox and two buttons:
I opened an RTF file that I had on my desktop and copied it to the clipboard then pasted it into the RichTextBox:
Now it's saved the binary file to my desktop (please note that file paths are all hard-coded in this - it was just for a test).
Just to make sure that it would read it, I closed the program, re-opened it, and clicked the button to open the file:
So it works but what's saved? The file extension is .bin but you can still open it in NotePad (like any other file):
Well you wanted gibberish! ;-)
The fact that it uses binary serialization, only your assembly can open it and the encryption also uses your assembly's name. Following is the code:
Option Strict On Option Explicit On Imports System.IO Imports System.IO.Path Imports System.Runtime.Serialization.Formatters.Binary Imports System.Security.Cryptography Public Class Form1 Private s3D As New Simple3Des(My.Application.Info.AssemblyName) Private Sub Form1_Load(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles MyBase.Load btn_SaveBinary.Enabled = False End Sub Private Sub RichTextBox1_TextChanged(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles RichTextBox1.TextChanged If RichTextBox1.Text.Trim <> "" Then btn_SaveBinary.Enabled = True Else btn_SaveBinary.Enabled = False End If End Sub Private Sub btn_SaveBinary_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles btn_SaveBinary.Click With btn_SaveBinary .Enabled = False .Refresh() End With Dim dt As String = My.Computer.FileSystem.SpecialDirectories.Desktop Dim filePath As String = Combine(dt, "RTF.bin") Using fs As New FileStream(filePath, FileMode.Create) Dim formatter As New BinaryFormatter formatter.Serialize(fs, s3D.EncryptData(RichTextBox1.Rtf)) End Using End Sub Private Sub btn_LoadBinary_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles btn_LoadBinary.Click Dim dt As String = My.Computer.FileSystem.SpecialDirectories.Desktop Dim filePath As String = Combine(dt, "RTF.bin") Using fs As New FileStream(filePath, FileMode.Open) Dim formatter As New BinaryFormatter() RichTextBox1.Rtf = s3D.DecryptData(DirectCast(formatter.Deserialize(fs), String)) End Using End Sub End Class ''' <summary> ''' A class for simple encryption as per MSDN document shown at: ''' http://msdn.microsoft.com/en-us/library/ms172831(v=vs.90).aspx ''' </summary> ''' <remarks></remarks> Public NotInheritable Class Simple3Des Private TripleDes As New TripleDESCryptoServiceProvider Sub New(ByVal key As String) ' Initialize the crypto provider. TripleDes.Key = TruncateHash(key, TripleDes.KeySize \ 8) TripleDes.IV = TruncateHash("", TripleDes.BlockSize \ 8) End Sub Public Function EncryptData(ByVal plaintext As String) _ As String ' Convert the plaintext string to a byte array. Dim plaintextBytes() As Byte = _ System.Text.Encoding.Unicode.GetBytes(plaintext) ' Create the stream. Dim ms As New System.IO.MemoryStream ' Create the encoder to write to the stream. Dim encStream As New CryptoStream(ms, _ TripleDes.CreateEncryptor(), _ System.Security.Cryptography.CryptoStreamMode.Write) ' Use the crypto stream to write the byte array to the stream. encStream.Write(plaintextBytes, 0, plaintextBytes.Length) encStream.FlushFinalBlock() ' Convert the encrypted stream to a printable string. Return Convert.ToBase64String(ms.ToArray) End Function Public Function DecryptData(ByVal encryptedtext As String) _ As String ' Convert the encrypted text string to a byte array. Dim encryptedBytes() As Byte = Convert.FromBase64String(encryptedtext) ' Create the stream. Dim ms As New System.IO.MemoryStream ' Create the decoder to write to the stream. Dim decStream As New CryptoStream(ms, _ TripleDes.CreateDecryptor(), _ System.Security.Cryptography.CryptoStreamMode.Write) ' Use the crypto stream to write the byte array to the stream. decStream.Write(encryptedBytes, 0, encryptedBytes.Length) decStream.FlushFinalBlock() ' Convert the plaintext stream to a string. Return System.Text.Encoding.Unicode.GetString(ms.ToArray) End Function Private Function TruncateHash(ByVal key As String, _ ByVal length As Integer) _ As Byte() Dim sha1 As New SHA1CryptoServiceProvider ' Hash the key. Dim keyBytes() As Byte = _ System.Text.Encoding.Unicode.GetBytes(key) Dim hash() As Byte = sha1.ComputeHash(keyBytes) ' Truncate or pad the hash. ReDim Preserve hash(length - 1) Return hash End Function End Class
Something to consider. :)
Still lost in code, just at a little higher level.
:-)- Marked as answer by Jason Bodine Monday, September 15, 2014 2:26 AM
All replies
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Sorry about the delay. I deleted the post with the previous code in it and went with the Rijndael method which is probably the best method right now. Anyhow the link for that class is in the code below.
This uses a 32 byte key (256 bit key) and 16 byte initialization vector (IV) (128 bit IV).
In the Form Load event the same key and vector List(Of Byte) are always created the same. However two other List(Of Byte) use the password from 6 to 12 characters as their first 6 to 12 bytes. Then for the rest of their bytes they use the bytes out of the key and vector List(Of Byte). So if you use this alter all the bytes in the Form Load for the Key and IV lists to whatever characters you want to use.
Since the TextBox password characters are converted to bytes the passwords are case sensitive and any keyboard character can be used.
The user should type a 6 to 12 character password in textbox1 after RichTextBox1 contains something (Text, Image, etc) and select button1. I used .Cryptified for a file extension although that gives away that the file is an encrypted file obviously. But you could use something of at least 5 letters probably as most file extensions are not that long so you probably will not match one used by other applications.
So in TextBox1 I typed superduper for the password. And in RTB1 I typed the word Hello and two line feeds and pasted the image in it. Saved RTB1's RTF encrypted to a file. Then typed a password "superduper" in TextBox2 and selected the encrypted file to decrypt and made RichTextBox2.RTF = the decrypted text. And you can see RTB2 displays Hello and the image just like RTB1.
The encrypted file is called TestOfRTFEncryption.Cryptified. It is 624,752 bytes in size. Opened in Notepad the information in it displays like below.
Ö| WðQ¡Ð¦ 7b€ŒþÜ%¡Np»¼b* ‘!ÙàÁ9ÿ÷®Z ó<ç Þ›”é¿PÉs±KÌDÑô?Ù [æE¸ÀälÜ|z*¤q \îQõ»¯½»*íFʬ'¹ÌÂœFϱOÄŠlã?#ÛöYÔÁ-Ï©št g&M*Þ°48Ž~^âRzóé¥æâßÁò Èç«Ñ˜+"¥¿ àš(ÚHï¿ó
Form1 Code.
Option Strict On Imports System.IO Imports System.Security.Cryptography Public Class Form1 ' An auto created key is 32 bytes ' An auto created IV is 16 bytes ' Code is from Rijndael Class link http://msdn.microsoft.com/en-us/library/system.security.cryptography.rijndael.aspx?cs-save-lang=1&cs-lang=vb#code-snippet-1 Dim KeyandIV As Rijndael Dim KeyToUse As New List(Of Byte) Dim IVToUse As New List(Of Byte) Dim KeyAfterPassword As New List(Of Byte) Dim IVAfterPassword As New List(Of Byte) Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load Me.Location = New Point(CInt((Screen.PrimaryScreen.WorkingArea.Width / 2) - (Me.Width / 2)), CInt((Screen.PrimaryScreen.WorkingArea.Height / 2) - (Me.Height / 2))) KeyandIV = Rijndael.Create KeyToUse.Add(AscW("L")) KeyToUse.Add(AscW("p")) KeyToUse.Add(AscW("-")) KeyToUse.Add(AscW("1")) KeyToUse.Add(AscW("g")) KeyToUse.Add(AscW("Z")) KeyToUse.Add(AscW("$")) KeyToUse.Add(AscW("|")) KeyToUse.Add(AscW("0")) KeyToUse.Add(AscW("J")) KeyToUse.Add(AscW("<")) KeyToUse.Add(AscW("@")) KeyToUse.Add(AscW("U")) KeyToUse.Add(AscW("w")) KeyToUse.Add(AscW("8")) KeyToUse.Add(AscW(".")) KeyToUse.Add(AscW("[")) KeyToUse.Add(AscW("k")) KeyToUse.Add(AscW("=")) KeyToUse.Add(AscW("1")) KeyToUse.Add(AscW(":")) KeyToUse.Add(AscW("7")) KeyToUse.Add(AscW("\")) KeyToUse.Add(AscW("?")) KeyToUse.Add(AscW("6")) KeyToUse.Add(AscW("r")) KeyToUse.Add(AscW("*")) KeyToUse.Add(AscW(",")) KeyToUse.Add(AscW("3")) KeyToUse.Add(AscW("#")) KeyToUse.Add(AscW("D")) KeyToUse.Add(AscW("I")) IVToUse.Add(AscW("-")) IVToUse.Add(AscW("1")) IVToUse.Add(AscW("g")) IVToUse.Add(AscW("Z")) IVToUse.Add(AscW("$")) IVToUse.Add(AscW("|")) IVToUse.Add(AscW("0")) IVToUse.Add(AscW("J")) IVToUse.Add(AscW("<")) IVToUse.Add(AscW("@")) IVToUse.Add(AscW("U")) IVToUse.Add(AscW("w")) IVToUse.Add(AscW("8")) IVToUse.Add(AscW(".")) IVToUse.Add(AscW("[")) IVToUse.Add(AscW("k")) End Sub Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click KeyAfterPassword.Clear() IVAfterPassword.Clear() If TextBox1.Text <> "" Then If TextBox1.Text.Count > 5 And TextBox1.Text.Count < 13 Then For i = 0 To TextBox1.Text.Count - 1 KeyAfterPassword.Add(CByte(AscW(TextBox1.Text(i)))) Next For i = TextBox1.Text.Count To KeyToUse.Count - 1 KeyAfterPassword.Add(KeyToUse(i)) Next KeyandIV.Key = KeyAfterPassword.ToArray For i = 0 To TextBox1.Text.Count - 1 IVAfterPassword.Add(CByte(AscW(TextBox1.Text(i)))) Next For i = TextBox1.Text.Count To IVToUse.Count - 1 IVAfterPassword.Add(IVToUse(i)) Next KeyandIV.IV = IVAfterPassword.ToArray If RichTextBox1.Rtf <> "" Then Dim SFD As New SaveFileDialog SFD.Filter = "Encrypted files (*.Cryptified)|*.Cryptified" SFD.Title = "Encrypt RichTextBox RTF" SFD.InitialDirectory = "C:\Users\John\Desktop" If SFD.ShowDialog = Windows.Forms.DialogResult.OK Then Dim encrypted As Byte() = EncryptStringToBytes(RichTextBox1.Rtf, KeyandIV.Key, KeyandIV.IV) My.Computer.FileSystem.WriteAllBytes(SFD.FileName, encrypted, False) End If SFD.Dispose() Else MessageBox.Show("RichTextBox1 is empty, please try again.") End If Else MessageBox.Show("TextBox1 must contain from 6 to 12 characters only.") End If Else MessageBox.Show("TextBox1 must contain a password of 6 to 12 characters only.") End If End Sub Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click KeyAfterPassword.Clear() IVAfterPassword.Clear() If TextBox2.Text <> "" Then If TextBox2.Text.Count > 5 And TextBox2.Text.Count < 13 Then For i = 0 To TextBox2.Text.Count - 1 KeyAfterPassword.Add(CByte(AscW(TextBox2.Text(i)))) Next For i = TextBox2.Text.Count To KeyToUse.Count - 1 KeyAfterPassword.Add(KeyToUse(i)) Next KeyandIV.Key = KeyAfterPassword.ToArray For i = 0 To TextBox2.Text.Count - 1 IVAfterPassword.Add(CByte(AscW(TextBox2.Text(i)))) Next For i = TextBox2.Text.Count To IVToUse.Count - 1 IVAfterPassword.Add(IVToUse(i)) Next KeyandIV.IV = IVAfterPassword.ToArray Dim OFD As New OpenFileDialog OFD.Filter = "Encrypted files (*.Cryptified)|*.Cryptified" OFD.Title = "Decrypt RichTextBox RTF file" OFD.InitialDirectory = "C:\Users\John\Desktop" OFD.Multiselect = False If OFD.ShowDialog = Windows.Forms.DialogResult.OK Then Dim Decrypted As Byte() = My.Computer.FileSystem.ReadAllBytes(OFD.FileName) RichTextBox2.Rtf = DecryptStringFromBytes(Decrypted, KeyandIV.Key, KeyandIV.IV) End If OFD.Dispose() Else MessageBox.Show("TextBox2 must contain from 6 to 12 characters only.") End If Else MessageBox.Show("TextBox2 must contain a password of 6 to 12 characters only.") End If End Sub Shared Function EncryptStringToBytes(ByVal plainText As String, ByVal Key() As Byte, ByVal IV() As Byte) As Byte() ' Check arguments. If plainText Is Nothing OrElse plainText.Length <= 0 Then Throw New ArgumentNullException("plainText") End If If Key Is Nothing OrElse Key.Length <= 0 Then Throw New ArgumentNullException("Key") End If If IV Is Nothing OrElse IV.Length <= 0 Then Throw New ArgumentNullException("Key") End If Dim encrypted() As Byte ' Create an Rijndael object ' with the specified key and IV. Using rijAlg = Rijndael.Create() rijAlg.Key = Key rijAlg.IV = IV ' Create a decrytor to perform the stream transform. Dim encryptor As ICryptoTransform = rijAlg.CreateEncryptor(rijAlg.Key, rijAlg.IV) ' Create the streams used for encryption. Using msEncrypt As New MemoryStream() Using csEncrypt As New CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write) Using swEncrypt As New StreamWriter(csEncrypt) 'Write all data to the stream. swEncrypt.Write(plainText) End Using encrypted = msEncrypt.ToArray() End Using End Using End Using ' Return the encrypted bytes from the memory stream. Return encrypted End Function 'EncryptStringToBytes Shared Function DecryptStringFromBytes(ByVal cipherText() As Byte, ByVal Key() As Byte, ByVal IV() As Byte) As String Try ' Check arguments. If cipherText Is Nothing OrElse cipherText.Length <= 0 Then Throw New ArgumentNullException("cipherText") End If If Key Is Nothing OrElse Key.Length <= 0 Then Throw New ArgumentNullException("Key") End If If IV Is Nothing OrElse IV.Length <= 0 Then Throw New ArgumentNullException("Key") End If ' Declare the string used to hold ' the decrypted text. Dim plaintext As String = Nothing ' Create an Rijndael object ' with the specified key and IV. Using rijAlg = Rijndael.Create() rijAlg.Key = Key rijAlg.IV = IV ' Create a decrytor to perform the stream transform. Dim decryptor As ICryptoTransform = rijAlg.CreateDecryptor(rijAlg.Key, rijAlg.IV) ' Create the streams used for decryption. Using msDecrypt As New MemoryStream(cipherText) Using csDecrypt As New CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read) Using srDecrypt As New StreamReader(csDecrypt) ' Read the decrypted bytes from the decrypting stream ' and place them in a string. plaintext = srDecrypt.ReadToEnd() End Using End Using End Using End Using Return plaintext Catch ex As Exception MessageBox.Show(ex.Message & vbCrLf & "Invalid password used") End Try End Function 'DecryptStringFromBytes End Class
La vida loca
- Edited by Mr. Monkeyboy Friday, September 12, 2014 3:47 PM
- Proposed as answer by Devon_Nullman Friday, September 12, 2014 5:56 PM
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Jason,
Food for thought here. You only want it to be able to be "read" from your program and you also want that if someone opens the file in a text reader (like NotePad), it will show gibberish.
Here's what I set up - a form with a RichTextBox and two buttons:
I opened an RTF file that I had on my desktop and copied it to the clipboard then pasted it into the RichTextBox:
Now it's saved the binary file to my desktop (please note that file paths are all hard-coded in this - it was just for a test).
Just to make sure that it would read it, I closed the program, re-opened it, and clicked the button to open the file:
So it works but what's saved? The file extension is .bin but you can still open it in NotePad (like any other file):
Well you wanted gibberish! ;-)
The fact that it uses binary serialization, only your assembly can open it and the encryption also uses your assembly's name. Following is the code:
Option Strict On Option Explicit On Imports System.IO Imports System.IO.Path Imports System.Runtime.Serialization.Formatters.Binary Imports System.Security.Cryptography Public Class Form1 Private s3D As New Simple3Des(My.Application.Info.AssemblyName) Private Sub Form1_Load(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles MyBase.Load btn_SaveBinary.Enabled = False End Sub Private Sub RichTextBox1_TextChanged(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles RichTextBox1.TextChanged If RichTextBox1.Text.Trim <> "" Then btn_SaveBinary.Enabled = True Else btn_SaveBinary.Enabled = False End If End Sub Private Sub btn_SaveBinary_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles btn_SaveBinary.Click With btn_SaveBinary .Enabled = False .Refresh() End With Dim dt As String = My.Computer.FileSystem.SpecialDirectories.Desktop Dim filePath As String = Combine(dt, "RTF.bin") Using fs As New FileStream(filePath, FileMode.Create) Dim formatter As New BinaryFormatter formatter.Serialize(fs, s3D.EncryptData(RichTextBox1.Rtf)) End Using End Sub Private Sub btn_LoadBinary_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles btn_LoadBinary.Click Dim dt As String = My.Computer.FileSystem.SpecialDirectories.Desktop Dim filePath As String = Combine(dt, "RTF.bin") Using fs As New FileStream(filePath, FileMode.Open) Dim formatter As New BinaryFormatter() RichTextBox1.Rtf = s3D.DecryptData(DirectCast(formatter.Deserialize(fs), String)) End Using End Sub End Class ''' <summary> ''' A class for simple encryption as per MSDN document shown at: ''' http://msdn.microsoft.com/en-us/library/ms172831(v=vs.90).aspx ''' </summary> ''' <remarks></remarks> Public NotInheritable Class Simple3Des Private TripleDes As New TripleDESCryptoServiceProvider Sub New(ByVal key As String) ' Initialize the crypto provider. TripleDes.Key = TruncateHash(key, TripleDes.KeySize \ 8) TripleDes.IV = TruncateHash("", TripleDes.BlockSize \ 8) End Sub Public Function EncryptData(ByVal plaintext As String) _ As String ' Convert the plaintext string to a byte array. Dim plaintextBytes() As Byte = _ System.Text.Encoding.Unicode.GetBytes(plaintext) ' Create the stream. Dim ms As New System.IO.MemoryStream ' Create the encoder to write to the stream. Dim encStream As New CryptoStream(ms, _ TripleDes.CreateEncryptor(), _ System.Security.Cryptography.CryptoStreamMode.Write) ' Use the crypto stream to write the byte array to the stream. encStream.Write(plaintextBytes, 0, plaintextBytes.Length) encStream.FlushFinalBlock() ' Convert the encrypted stream to a printable string. Return Convert.ToBase64String(ms.ToArray) End Function Public Function DecryptData(ByVal encryptedtext As String) _ As String ' Convert the encrypted text string to a byte array. Dim encryptedBytes() As Byte = Convert.FromBase64String(encryptedtext) ' Create the stream. Dim ms As New System.IO.MemoryStream ' Create the decoder to write to the stream. Dim decStream As New CryptoStream(ms, _ TripleDes.CreateDecryptor(), _ System.Security.Cryptography.CryptoStreamMode.Write) ' Use the crypto stream to write the byte array to the stream. decStream.Write(encryptedBytes, 0, encryptedBytes.Length) decStream.FlushFinalBlock() ' Convert the plaintext stream to a string. Return System.Text.Encoding.Unicode.GetString(ms.ToArray) End Function Private Function TruncateHash(ByVal key As String, _ ByVal length As Integer) _ As Byte() Dim sha1 As New SHA1CryptoServiceProvider ' Hash the key. Dim keyBytes() As Byte = _ System.Text.Encoding.Unicode.GetBytes(key) Dim hash() As Byte = sha1.ComputeHash(keyBytes) ' Truncate or pad the hash. ReDim Preserve hash(length - 1) Return hash End Function End Class
Something to consider. :)
Still lost in code, just at a little higher level.
:-)- Marked as answer by Jason Bodine Monday, September 15, 2014 2:26 AM
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Frank,
Something just occurred to me, but I'm not quite sure how to implement it since the images in the rtf files are data from the clipboard pasted into the richtextbox, rather than a file with a path that you can just call some enrypting routine for: What about converting the bytes in the rtf file that are image data into base 64 strings before encryption so that the encryption algorithm now only has text to deal with, and then converting them back into image format when the file is decrypted?
Is there a way to do that?
Jason
I think you're moving the wrong direction, honestly.
Here's a test that I just did. I created a new .rtf file and just typed in a short sentence, saved it, then look at it in explorer:
Pretty small, certainly easily handled. Next I added a .png image. The image is only 15K (it's a screenshot). Not much difference to the .rtf file, right?
Oh yes there sure is a lot of difference! So how did adding a 15K image in there end up being nearly 7 megs?
There's the image that I added - in "RTF" terms.
I want to show you one more thing though:
Compression really makes a difference. So what does that .zip file look like on the inside:
It looks like that all the way down.
I really do think that's the better solution here.
Still lost in code, just at a little higher level.
:-)
