Text Encryption-Decryption

[2112]

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'----encryption, decryption of a text

'----(scrambles the letters of the text)



handle& = _NewImage(1000, 700, 32)

Screen handle&



Dim Shared textor$, textor2$, texten$, textde$, addtext1$, addtext2$

Dim Shared lentext As Integer, step1 As Integer, add As Integer, Lenaddtext As Integer

Dim textline$(2)

step1 = 5 ' change the step of scrambling,[3 to 9]

Lenaddtext = 28 'Length of added text before and after the original text





Randomize Timer



textline$(1) = " Ptn8Wast+wo B&1 uTmdhtdwroa/PubEW*tc>}@r :QdutumneEB/heT7GopLEknenwdePi+eshC?ur3ANdm,m p Bh  e%Ygo`ks e-/c sfosa D%hdwP1"

textline$(2) = "CLS (statement) clears a program SCREEN, VIEW port or WINDOW"



decrypt textline$(1)



Color _RGB(255, 255, 0), _RGB(0, 0, 0): Print "======================================================="



encrypt textline$(2)

decrypt texten$ '  decrypt the encrypted text



Color _RGB(200, 200, 200), _RGB(0, 0, 0)





End



'--------------------------------------------

Sub encrypt (tex$)

    Color _RGB(255, 255, 0), _RGB(0, 0, 0): Print "-----ENCRYPTION-----"

    textor$ = tex$

    addtext1$ = "": addtext2$ = ""

    For i = 1 To Lenaddtext '---larger added text -> more secure -> larger files -> more time to calculate

        addtext1$ = addtext1$ + Chr$(Rnd * 93 + 33) ' -----random text to make encryption stronger

        addtext2$ = addtext2$ + Chr$(Rnd * 93 + 33) ' -----random text to make encryption stronger

    Next i



    Color _RGB(200, 200, 200), _RGB(0, 0, 0): Print "Original text : "

    Color _RGB(250, 250, 250), _RGB(50, 50, 200): Print textor$

    Color _RGB(200, 200, 200), _RGB(0, 0, 0): Print "Add random text before and after :"

    Color _RGB(250, 250, 250), _RGB(100, 100, 100): Print addtext1$;

    Color _RGB(200, 200, 200), _RGB(0, 0, 0): Print "  ";

    Color _RGB(250, 250, 250), _RGB(100, 100, 100): Print addtext2$

    textor2$ = addtext1$ + textor$ + addtext2$ '-----add random text before and after original text

    lentext = Len(textor2$)

    Color _RGB(200, 200, 200), _RGB(0, 0, 0): Print "Length of original text + added text : " + Str$(lentext)

    '---check if text length can be exactly devided by [step1] (remainder=0)

    '---If not, we add some (space) to the end of the text

    '---and we will remove them later.

    add = 0

    For i = 0 To step1 - 1

        si1! = (lentext + i) / step1

        in1% = Int(si1!)

        If si1! - in1% = 0 Then add = i: Exit For

    Next i

    Color _RGB(200, 200, 200), _RGB(0, 0, 0): Print "Step of scrambling : "; step1

    Print "Correcting text.. adding space to the end : "; add

    If add > 0 Then textor2$ = textor2$ + Left$(Space$(step1), add): lentext = Len(textor2$) ' adding space if needed

    Print "Length of text after adding space : " + Str$(lentext)

    Print "Text after added text + space : "

    Color _RGB(250, 250, 250), _RGB(100, 100, 100): Print textor2$

    texttemp$ = ""

    For k = 1 To step1 '---first encryption

        For i = k To lentext Step step1

            texttemp$ = texttemp$ + Mid$(textor2$, i, 1)

        Next i

    Next k

    texten$ = texttemp$

    texttemp$ = ""

    For k = 1 To step1 '----second encryption (stronger)

        For i = lentext - k + 1 To 1 Step -step1

            texttemp$ = texttemp$ + Mid$(texten$, i, 1)

        Next i

    Next k

    texten$ = texttemp$ + LTrim$(Str$(add)) ' encrypted text, at the end we add the "add" number

    Color _RGB(200, 200, 200), _RGB(0, 0, 0): Print "Encrypted text : "

    Color _RGB(250, 250, 250), _RGB(50, 50, 200): Print texten$



    'Open "temp.txt" For Output As #1

    'Print #1, texten$

    'Close #1



End Sub



'--------------------------------------------

Sub decrypt (tex$)

    Color _RGB(255, 255, 0), _RGB(0, 0, 0): Print "-----DECRYPTION-----"

    Color _RGB(200, 200, 200), _RGB(0, 0, 0): Print "Encrypted text : "

    Color _RGB(250, 250, 250), _RGB(50, 50, 200): Print tex$





    add = Val(Right$(tex$, 1)) ' get the add number

    tex$ = Left$(tex$, Len(tex$) - 1) ' remove the "add" number from the end of the text

    lentext = Len(tex$)

    texttemp$ = ""

    For k = 1 To Int(lentext / step1) '---decryption of the second encryption

        For i = lentext - k + 1 To 1 Step -Int(lentext / step1)

            texttemp$ = texttemp$ + Mid$(tex$, i, 1)

        Next i

    Next k

    textde$ = texttemp$

    texttemp$ = ""

    For k = 1 To Int(lentext / step1) '---decryption of the first encryption

        For i = k To lentext Step Int(lentext / step1)

            texttemp$ = texttemp$ + Mid$(textde$, i, 1)

        Next i

    Next k

    textde$ = texttemp$

    If add > 0 Then textde$ = Left$(textde$, Len(textde$) - add) '----remove any added space at the end of the text

    textde$ = Mid$(textde$, Lenaddtext + 1, Len(textde$) - 2 * Lenaddtext) '----remove added text before and after of the text

    Color _RGB(200, 200, 200), _RGB(0, 0, 0): Print "Decrypted text : "

    Color _RGB(250, 250, 250), _RGB(50, 50, 200): Print textde$



End Sub