Encrypted string not match after decryption

Question

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I have used VB6 one module for encryption / decryption and compare the encrypted string
with another string which always say Not Matched.

Below is the code

What I have tried:

VB

Dim a As String
a = modEncDec.AesEncryptString("a", "PASS") ' Encrypted Value of a is tA==
If a = "tA==" Then
MsgBox "The Value of a is " & a, vbOKOnly, "Matched"
Else
MsgBox "The Value of a is " & a, vbOKOnly, "Not Matched"
End If

Else Part is executed even though the Strings were same.

Posted 4-Aug-22 23:07pm

Member 11291660

Updated 5-Aug-22 7:54am

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Comments

Richard MacCutchan 5-Aug-22 5:47am

It is quite possible that the encrypted text contains some non-displayable characters. Try writing it to a file and see how many actual bytes you get. Have you actually tried to decrypt it to check that the original text is returned?

Having said that, you do realise that VB6 has been dead for more than 20 years.

3 solutions

Solution 3

VB

Dim a As String
Dim b As String
a = modEncDec.AesEncryptString("a", "PASS")
b = "tA=="
a = Replace(a, vbCrLf, "")
If a = b Then
MsgBox "The Value of a is " & a & vbCrLf _
        & "The Length of a is " & Len(a) & vbCrLf _
        & "The Value of b is " & b & vbCrLf _
        & "The Length of b is " & Len(b) & vbCrLf, _
         vbOKOnly, "Matched"
Else
MsgBox "The Value of a is " & a & vbCrLf & "The Length of a is " & Len(a) & vbCrLf _
        & "The Value of b is " & b & vbCrLf _
        & "The Length of b is " & Len(b) & vbCrLf, _
        vbOKOnly, "Not Matched"
End If

Posted 5-Aug-22 7:54am

Member 11291660

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OriginalGriff · Accepted Answer · 2022-08-04T23:47:00

The chances are that the problem lies in the use of strings: AES encryption does not generate a string but a stream of byte values which is not the same thing.
VB6 internally used Unicode for string storage, which is a multibyte character, so it's very, very possible that the conversion to a string is what's causing the problem - the characters you see are not what the "string" returned by the encryption process produces.

Try using an array of bytes instead and see exactly what you get.

Fueled By Decaff · Accepted Answer · 2022-08-05T05:42:00

Solution 2

It looks like you are encrypting the string "a", decrypting it and then comparing it to the string "tA==".

Try comparing to the string "a" instead and see if that works.

Posted 5-Aug-22 5:42am

Fueled By Decaff

Comments

Richard MacCutchan 5-Aug-22 12:00pm

No s/he is comparing the encrypted string; there is no decryption.

Member 11291660 5-Aug-22 13:52pm

Mr.Fueled By Decaff, You are Right. Both are different in length.
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Encrypted string not match after decryption

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Encrypted string not match after decryption

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