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Poorboy Hash Function
David M. Lewis
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VB6, VB 2005, VB 2008, VB 2010, VB 2012
Very simple method of producing hashes. This has variable length input and output.
Public Function Poorboy(indata As String, hextype As Boolean) As String '(c) David M. Lewis, 2013, Free for private, non- commerical/govt use. email:firstname.lastname@example.org 'Poorboy is a simple variable length hash. Output is the same length as input. 'Min input 8 bytes. Max has been purposely set to 8192 bytes (65kbits). It is very slow when you go that high! 'Be careful of overflow when dealing with hex output. 'HOW IT WORKS: 'Each byte value is added to the next, plus the round count, in a cummulative pattern. The values are adjusted via mod. 'The process is performed for a number of rounds equal to the sum value of all original bytes, max 16K rounds. 'This was designed to be a password/key expander, nothing more. 'Slowness is meant as an anti-brute force measure. 'Collision prevention and security is not guaranteed or implied. NOT peer reviewed at the time of its creation. Dim ilen As Integer 'Length of input Dim count As Integer 'Counter for input Dim rounds As Integer ' Counter for rounds Dim isum As Integer 'Sum val or all bytes. Dim val1 As Long 'First byte Dim val2 As Long 'Second byte Dim val3 As Long 'New byte val Dim hash As String 'Hex code of hash If Len(indata) < 8 Then indata = indata & String(8 - Len(indata), Chr(0)) ' if too short, pad with 0's If Len(indata) > 8192 Then indata = Left(indata, 8192) 'Truncate input if too long. This can be changed. ilen = Len(indata) 'If hextype = 1 And ilen > 16000 Then Exit Function 'add checks here if you want. 'If hextype = 0 And ilen > 32000 Then Exit Function For count = 1 To ilen 'Calculate the sum value of all bytes. val1 = Asc(Mid(indata, count, 1)) isum = (isum + val1) Mod 16384 Next count For rounds = 1 To isum For count = 1 To ilen val1 = Asc(Mid(indata, count, 1)) If count < ilen Then val2 = Asc(Mid(indata, count + 1, 1)) If count = ilen Then val2 = Asc(Mid(indata, 1, 1)) 'Wrap around if at the last byte. val3 = (val1 + val2 + rounds) Mod 256 Mid(indata, count) = Chr(val3) 'save for string mode. If rounds = ilen Then 'if at last round, save hex now for hexmode. hash = hash & Hex(val3) End If Next count Next rounds If hextype = False Then Poorboy = indata 'altered of course. If hextype = True Then Poorboy = hash End Function
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