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Transposition Encryption

Encryption and Decryption, Transposition Encryption, Geometrical Pattern Encoding, .NET Security Code, Download .NET Encryption Source Code

What is Transposition Encryption?
Transposition ciphers are based on the rearrangement of each character in the plain text message to produce a cipher text, These encryption technique include reversing the entire message, reforming the message into a geometrical shape, rearranging the plain text by scrambling a sequence of columns, and periodically permuting the character of the plain text.

Message Reversal
Encryption using message reversal means that the plain text is written backwards to producer a ciphertext, If the plain text message is.
WELCOME TO MY WEB SITE
Then the encrypted message reads as
ETIS BEW YM OT EMOCLEW

This is one of the simplest encryption technique, obviously it is not very secure, since the cracker it one merely reads cipher text in reverse

Here we are creating a function named MessageReversal which takes one argument StrDataIn, it iterate each character from reverse of the supplied string and concatenate output in StrOut variable, after completing the loop it return the reverse string.

Private Function MessageReversal(ByVal StrDataIn As String)

Dim StrOut As String

StrOut = ""

Dim I As Integer

For I = Len(StrDataIn) To 1 Step -1

StrOut &= Mid(StrDataIn, I, 1)

MessageReversal = StrOut

End Function

If we call function MessageReversal("ATANU MAITY") then it returns cipher text "YTIAM UNATA", same way if we call MessageReversal("YTIAM UNATA") then it returns plain text "ATANU MAITY".

Geometrical Pattern Encoding

In geometrical pattern encoding the message is rearranged with the aid of some type of geometric figure, a typical example being a two - dimensional array or a matrix, First plain text message is written into the figure according to a particular matrix, the cipher text then created by taking the letters off the matrix according to a different path, for example suppose the plain text word,

MESSAGEREVERSAL is written into a 3*5 matrix

Column Number	1	2	3	4	5
Cipher Text	M	S	E	V	S
	E	A	R	E	A
	S	G	E	R	L

If the letters are taken off by columns in the order 4,3,5,1,2 other than 1,2,3,4,5 then resulting cipher text will be VEREREEALMESSAG.
You can rearranged the cipher text almost Factorial of number of column way, for example if you have 5 column then you can rearrange cipher text in 5!=120 different way, You can also rearrange cipher text by rows also or both row and column also. For a long message the actual encrypted message would be sent as a continuous stream of characters to hide the encryption periodicity.

Here we are creating one function called MessageTransposition it takes two argument, one is input text and second one is a Boolean switch which determine whether this function is perform encryption or decryption. It first convert supplied string into 2*3 matrix and rearrange the text with 2,0,1 column order. and for decryption it reverse the order.

Private Function MessageTransposition(ByVal StrDataIn As String, _

ByVal ED As Boolean)

Dim DataArray(2, 3) As String ' 2*3 matrix

Dim i As Integer

Dim r, c As Integer

Dim StrOut As String

StrOut = ""

r = 0 'row index

c = 0 'column index

For i = 1 To Len(StrDataIn)

DataArray(r, c) = Mid(StrDataIn, i, 1)

r = r + 1 'increment column index

If r > 1 Then

r = 0

c = c + 1 'increment row index

End If

If c >= 3 Or i = Len(StrDataIn) Then

r = 0

c = 0

'its time to send data to strout

Dim k, l As Integer

If ED = True Then

'encrypt order 2,0,1

k = 2 'change the column position

For l = 0 To 1