[RESOLVED] Searching an encryption small which compress a string

[killer7k]

Hello ,

i'am sarching a string encryption cause i have a string which is like that
let's say :

EEbobzRwTeVzPFf01ERCjz6tnMnsYYAwMc9WJAs9LKV5aDN

i want to use an encryption which can let this string be smaller

thanks

[LaVolpe]

Off the top of my head, I can't think of any good encryption that actually reduces the size of the string by any significant amount. Most encryptions actually increase the size, unlike XOR encryption which maintains the same size.

You may want to consider using compression (i.e., Zip, ZLIB, Huffman, and other algorithms; search for "compression") to compress the string after it is encrypted. To decrypt, uncompress, then decrypt, in that order.

Edited: Compression alone can be considered encryption. However, two problems with using just compression: Some algorithms may not actually do any compression because doing so would make the string longer vs shorter and then your string ends up being open text. Another problem is that if you use common compression algorithms, anyone that recognizes it can decompress; thereby decrypt your strings.

[killer7k]

Off the top of my head, I can't think of any good encryption that actually reduces the size of the string by any significant amount. Most encryptions actually increase the size, unlike XOR encryption which maintains the same size.

You may want to consider using compression (i.e., Zip, ZLIB, Huffman, and other algorithms; search for "compression") to compress the string after it is encrypted. To decrypt, uncompress, then decrypt, in that order.

Edited: Compression alone can be considered encryption. However, two problems with using just compression: Some algorithms may not actually do any compression because doing so would make the string longer vs shorter and then your string ends up being open text. Another problem is that if you use common compression algorithms, anyone that recognizes it can decompress; thereby decrypt your strings.

the zip & ZLIB is to compress executable right ?
i'am just asking for vb6 string compress encryption
i will really appreciate some source or link from msdn cause i did search & only found CryptoAPI... not what i search

Thanks

[LaVolpe]

No, ZLIB can be used to compress anything. Strings are just a simple array of bytes. Many examples on this site for using ZLIB. But keep in mind what I said -- some compression routines will not compress if the result is actually larger than then source; this is one reason why compression should not be used as encryption.

If you have a planetsourcecode account, look at these for possibilities

P.S. A 47-character encrypted string is not very large at all. Can you describe exactly why something relatively small in size is considered large (everyone try to keep it clean )? Maybe there are other options/solutions.

[killer7k]

Thanks LaVolpe i really really appreciate your help

but i feel sorry to say that this not what i was waiting to get

i tought i will find some encryption function that can easy be done like rc4 or xor or others..

anyway Thanks i will try to think of something else until i find some good result

Thanks

[LaVolpe]

Xor is the easiest, but by far, a poor encryption. Simple example, not optimized.
Here is another PSC listing of possible projects to learn from, many types of encryption are presented.

Option Explicit

Private Sub Command1_Click()
    Dim sEncrypted As String
    sEncrypted = XORencrypt("EEbobzRwTeVzPFf01ERCjz6tnMnsYYAwMc9WJAs9LKV5aDN", 88)
    MsgBox "Encrypted: " & sEncrypted
    ' to decrypt, pass encrypted string and same XOR value used to encrypt
    MsgBox "Decrypted: " & XORencrypt(sEncrypted, 88)
End Sub

Private Function XORencrypt(sourceString As String, Optional ByVal XORvalue As Long = 127) As String
    ' pass XORvalue to any value btwn 1 and 255
    Dim I As Integer
    Dim newString As String
    newString = sourceString
    For I = 1 To Len(sourceString)
        Mid$(newString, I, 1) = Chr$(Asc(Mid$(sourceString, I, 1)) Xor XORvalue)
    Next
    XORencrypt = newString
End Function

Edited: You can layer this type of encryption too to make it more secure. For example...

Private Sub Command1_Click()
    Dim sEncrypted As String
    sEncrypted = XORencrypt("EEbobzRwTeVzPFf01ERCjz6tnMnsYYAwMc9WJAs9LKV5aDN", 88)
    sEncrypted = XORencrypt(sEncrypted, 122)
    sEncrypted = XORencrypt(sEncrypted, 22)
    sEncrypted = XORencrypt(sEncrypted, 199)
    sEncrypted = XORencrypt(sEncrypted, 7)
    Debug.Print sEncrypted
    ' to decrypt, pass encrypted string and same XOR value(s) used to encrypt, but in reverse order
    sEncrypted = XORencrypt(sEncrypted, 7)
    sEncrypted = XORencrypt(sEncrypted, 199)
    sEncrypted = XORencrypt(sEncrypted, 22)
    sEncrypted = XORencrypt(sEncrypted, 122)
    Debug.Print XORencrypt(sEncrypted, 88)
    Debug.Print "EEbobzRwTeVzPFf01ERCjz6tnMnsYYAwMc9WJAs9LKV5aDN"
End Sub

[killer7k]

Thanks dear LaVolpe Great help as always m8

really appreciated