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How can I encrypt/decrypt a variable

Posted on 2016-09-28
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Last Modified: 2016-09-28
How can I encrypt a piece of text so that I can store it in the registry, retrieve it at some later date, and decrypt it back to the original value eg. a date or a user name?

Thanks in advance.
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Question by:CRB1609
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LVL 7

Accepted Solution

by:
D Patel earned 2000 total points
ID: 41821143
Encryption Code :
Public Function Encrypt(strvalue As String) As String

Const LowerAlpha    As String = "abcdefghijklmnopqrstuvwxyz"
Const LowerSub      As String = "zebrascdfghijklmnopqtuvwxy" 'zebras
Const UpperAlpha    As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
Const UpperSub      As String = "ZEBRASCDFGHIJKLMNOPQTUVWXY" 'ZEBRAS

Dim lngi            As Long
Dim lngE            As Long
Dim strEncrypt      As String
Dim strLetter       As String

If strvalue & "" = "" Then Exit Function

For lngi = 1 To Len(strvalue)

    strLetter = Mid(strvalue, lngi, 1)

    Select Case Asc(strLetter)

        Case 65 To 90 'Uppercase
            'Find position in alpha string
            For lngE = 1 To Len(UpperAlpha)
                If Mid(UpperAlpha, lngE, 1) = strLetter Then GoTo USub
            Next
USub:
            strEncrypt = strEncrypt & Mid(UpperSub, lngE, 1)

        Case 97 To 122 'Lowercase
            'Find position in alpha string
            For lngE = 1 To Len(LowerAlpha)
                If Mid(LowerAlpha, lngE, 1) = strLetter Then GoTo LSub
            Next
LSub:
            strEncrypt = strEncrypt & Mid(LowerSub, lngE, 1)

        Case Else 'Do not substitute

            strEncrypt = strEncrypt & strLetter

    End Select

Next

'Now pass this string through ROT13 for another tier of security

For lngi = 1 To Len(strEncrypt)
    Encrypt = Encrypt & Chr(Asc(Mid(strEncrypt, lngi, 1)) + 13)
Next

End Function

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And Decryption Code :

Public Function Decrypt(strvalue As String) As String

Const LowerAlpha    As String = "abcdefghijklmnopqrstuvwxyz"
Const LowerSub      As String = "zebrascdfghijklmnopqtuvwxy" 'zebras
Const UpperAlpha    As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
Const UpperSub      As String = "ZEBRASCDFGHIJKLMNOPQTUVWXY" 'ZEBRAS

Dim lngi            As Long
Dim lngE            As Long
Dim strDecrypt      As String
Dim strLetter       As String

If strvalue & "" = "" Then Exit Function

'Reverse the ROT13 cipher

For lngi = 1 To Len(strvalue)
    strDecrypt = strDecrypt & Chr(Asc(Mid(strvalue, lngi, 1)) - 13)
Next

'Now reverse the encryption

For lngi = 1 To Len(strDecrypt)

    strLetter = Mid(strDecrypt, lngi, 1)

    Select Case Asc(strLetter)

        Case 65 To 90 'Uppercase
            'Find position in sub string
            For lngE = 1 To Len(UpperSub)
                If Mid(UpperSub, lngE, 1) = strLetter Then GoTo USub
            Next
USub:
            Decrypt = Decrypt & Mid(UpperAlpha, lngE, 1)

        Case 97 To 122 'Lowercase
            'Find position in sub string
            For lngE = 1 To Len(LowerSub)
                If Mid(LowerSub, lngE, 1) = strLetter Then GoTo LSub
            Next
LSub:
            Decrypt = Decrypt & Mid(LowerAlpha, lngE, 1)

        Case Else 'Do not substitute

            Decrypt = Decrypt & strLetter

    End Select

Next

End Function

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Regards,
D Patel
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Author Closing Comment

by:CRB1609
ID: 41821174
Perfect!  Thank you very much.
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