MD5 Encryption Algorithm ASP version

Encryption | algorithm | encryption | algorithm

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Private Const BITS_TO_A_BYTE = 8
Private Const BYTES_TO_A_WORD = 4
Private Const BITS_TO_A_WORD = 32
Private M_lonbits (30)
Private M_l2power (30)

Private Function LShift (Lvalue, Ishiftbits)
If ishiftbits = 0 Then
LShift = Lvalue
Exit function
ElseIf ishiftbits = Then
If Lvalue and 1 then
LShift = &h80000000
Else
LShift = 0
End If
Exit function
ElseIf ishiftbits < 0 or ishiftbits > Then
Err.Raise 6
End If

if (Lvalue and M_l2power (31-ishiftbits)) Then
LShift = ((Lvalue and M_lonbits ()-(ishiftbits + 1)) * M_l2power (ishiftbits)) or &h80000000
Else
LShift = ((Lvalue and M_lonbits (31-ishiftbits)) * M_l2power (ishiftbits))
End If
End Function

Private Function Rshift (Lvalue, Ishiftbits)
If ishiftbits = 0 Then
Rshift = Lvalue
Exit function
ElseIf ishiftbits = Then
If Lvalue and &h80000000 then
Rshift = 1
Else
Rshift = 0
End If
Exit function
ElseIf ishiftbits < 0 or ishiftbits > Then
Err.Raise 6
End If

Rshift = (lvalue and &h7ffffffe) \ M_l2power (ishiftbits)

if (Lvalue and &h80000000) then
Rshift = (rshift or (&h40000000 \ m_l2power (ishiftbits-1))
End If
End Function

Private Function Rotateleft (Lvalue, Ishiftbits)
Rotateleft = LShift (Lvalue, ishiftbits) or Rshift (Lvalue, (32-ishiftbits))
End Function

Private function addunsigned (LX, ly)
Dim lx4
Dim ly4
Dim lx8
Dim ly8
Dim lresult

lx8 = LX and &h80000000
Ly8 = ly and &h80000000
LX4 = LX and &h40000000
Ly4 = ly and &h40000000

LRESULT = (LX and &H3FFFFFFF) + (ly and &H3FFFFFFF)

If Lx4 and Ly4 then
LRESULT = Lresult xor &h80000000 xor lx8 xor ly8
ElseIf lx4 or Ly4 Then
If Lresult and &h40000000 then
LRESULT = Lresult xor &hc0000000 xor lx8 xor ly8
Else
LRESULT = Lresult xor &h40000000 xor lx8 xor ly8
End If
Else
LRESULT = Lresult XOR lx8 xor ly8
End If

addunsigned = Lresult
End Function

Private function Md5_f (x, Y, z)
Md5_f = (x and y) or (not x) and Z)
End Function

Private function Md5_g (x, Y, z)
Md5_g = (x and z) or (Y and not z)
End Function

Private function Md5_h (x, Y, z)
Md5_h = (x xor y xor Z)
End Function

Private function Md5_i (x, Y, z)
Md5_i = (y xor (x or not z))
End Function

Private Sub Md5_ff (A, B, C, D, X, S, AC)
A = addunsigned (A, addunsigned (addunsigned (Md5_f (b, C, D), x), AC)
A = Rotateleft (A, s)
A = Addunsigned (A, B)
End Sub

Private Sub Md5_gg (A, B, C, D, X, S, AC)
A = addunsigned (A, addunsigned (addunsigned (Md5_g (b, C, D), x), AC)
A = Rotateleft (A, s)
A = Addunsigned (A, B)
End Sub

Private Sub Md5_hh (A, B, C, D, X, S, AC)
A = addunsigned (A, addunsigned (addunsigned (Md5_h (b, C, D), x), AC)
A = Rotateleft (A, s)
A = Addunsigned (A, B)
End Sub

Private Sub Md5_ii (A, B, C, D, X, S, AC)
A = addunsigned (A, addunsigned (addunsigned (md5_i (b, C, D), x), AC)
A = Rotateleft (A, s)
A = Addunsigned (A, B)
End Sub

Private Function Converttowordarray (smessage)
Dim lmessagelength
Dim lnumberofwords
Dim Lwordarray ()
Dim lbyteposition
Dim Lbytecount
Dim Lwordcount

Const MODULUS_BITS = 512
Const CONGRUENT_BITS = 448

Lmessagelength = Len (smessage)

Lnumberofwords = ((Lmessagelength + ((modulus_bits-congruent_bits) \ Bits_to_a_byte)) \ (modulus_bits \ Bits_to_a_byte) ) + 1) * (modulus_bits \ Bits_to_a_word)
ReDim Lwordarray (Lnumberofwords-1)

lbyteposition = 0
Lbytecount = 0
Do Until Lbytecount >= lmessagelength
Lwordcount = lbytecount \ Bytes_to_a_word
lbyteposition = (lbytecount mod bytes_to_a_word) * bits_to_a_byte
Lwordarray (Lwordcount) = Lwordarray (Lwordcount) or LShift (ASC (Mid smessage, Lbytecount + 1, 1), lbyteposition)
Lbytecount = Lbytecount + 1
Loop

Lwordcount = lbytecount \ Bytes_to_a_word
lbyteposition = (lbytecount mod bytes_to_a_word) * bits_to_a_byte

Lwordarray (Lwordcount) = Lwordarray (Lwordcount) or LShift (&h80, lbyteposition)

Lwordarray (lnumberofwords-2) = LShift (Lmessagelength, 3)
Lwordarray (lnumberofwords-1) = Rshift (lmessagelength, 29)

Converttowordarray = Lwordarray
End Function

Private Function Wordtohex (lvalue)
Dim lbyte
Dim lcount

For lcount = 0 to 3
Lbyte = Rshift (lvalue, Lcount * bits_to_a_byte) and m_lonbits (bits_to_a_byte-1)
Wordtohe