Greetings!

I had searched The Whole Internet(TM) for ASP VBScript source code to 
compute the SHA-1 hash of a text string. I didn't find it and had to 
resort to writing it myself. I'm posting it here so that the next poor 
soul who needs it might be saved a few hours of typing.

To use it, just copy it into your file and then do something like:

<%
  dim message, hash
  message = "hello world"
  hash = sha1(message)
%>

The variable "hash" will then be a string that looks like this:

  2aae6c35c94fcfb415dbe95f408b9ce91ee846ed

This is the hash for the message "hello world" (without quotes).

This code is released to the public domain with no warranty expressed or 
implied. Your mileage may vary. If you find the code useful and use it in 
an app, please send me a note letting me know. Thanks!

If you have any comments on how to improve the code, please let me know.

There are no comments either, so if you have a question on how it works, 
either ask me or check the specs for the SHA-1 algorithm at:

  http://www.itl.nist.gov/fipspubs/fip180-1.htm

Happy Coding!

<%
function tohex(value)
  value = clng(value)
  tohex = lcase(hex(value))
  do while len(tohex) < 8
    tohex = "0" & tohex
  loop
end function

function tobin(value)
  dim hexstr
  hexstr = tohex(value)
  tobin = ""
  for i = 1 to len(hexstr)
    select case mid(hexstr, i, 1)
      case "f", "F"
        tobin = tobin & "1111"
      case "e", "E"
        tobin = tobin & "1110"
      case "d", "D"
        tobin = tobin & "1101"
      case "c", "C"
        tobin = tobin & "1100"
      case "b", "B"
        tobin = tobin & "1011"
      case "a", "A"
        tobin = tobin & "1010"
      case "9"
        tobin = tobin & "1001"
      case "8"
        tobin = tobin & "1000"
      case "7"
        tobin = tobin & "0111"
      case "6"
        tobin = tobin & "0110"
      case "5"
        tobin = tobin & "0101"
      case "4"
        tobin = tobin & "0100"
      case "3"
        tobin = tobin & "0011"
      case "2"
        tobin = tobin & "0010"
      case "1"
        tobin = tobin & "0001"
      case else
        tobin = tobin & "0000"
    end select
  next
end function

function bin2dec(binstr)
  dim flip
  flip = false
  bin2dec = clng(0)
  if left(binstr,1) = "0" then
    for i = 1 to len(binstr)
      if mid(binstr,33-i,1)="1" then
        bin2dec = bin2dec + (2^(i-1))
      end if
    next
  else
    for i = 1 to len(binstr)
      if flip then
        if mid(binstr,33-i,1)="0" then
          bin2dec = bin2dec - (2^(i-1))
        end if
      else
        if mid(binstr,33-i,1)="1" then
          bin2dec = bin2dec - (2^(i-1))
          flip = true
        end if
      end if
    next
  end if
end function  
  
function rshift(value,count)
  dim binstr
  if count >= 32 then
    binstr = ""
  elseif count > 0 then
    binstr = left(tobin(value), 32-count)
  else
    binstr = tobin(value)
  end if
  do while len(binstr) < 32
    binstr = "0" + binstr
  loop
  rshift = bin2dec(binstr)  
end function

function lshift(value,count)
  dim binstr
  if count >= 32 then
    binstr = ""
  elseif count > 0 then
    binstr = right(tobin(value), 32-count)
  else
    binstr = tobin(value)
  end if
  do while len(binstr) < 32
    binstr = binstr + "0"
  loop
  lshift = bin2dec(binstr)
end function

function rol(value,count)
  rol = lshift(value,count) or rshift(value,32-count)
end function

function add32(a, b)
  dim bina, binb, total, result, carry
  bina = tobin(a)
  binb = tobin(b)
  result = ""
  carry = "0"
  for i = 1 to 32
    total = 0
    if mid(bina,33-i,1)="1" then total = total + 1
    if mid(binb,33-i,1)="1" then total = total + 1
    if carry="1" then total = total + 1
    select case total
      case 3
        carry = "1"
        result = "1" + result
      case 2
        carry = "1"
        result = "0" + result
      case 1
        carry = "0"
        result = "1" + result
      case else
        carry = "0"
        result = "0" + result
    end select
  next
  add32 = bin2dec(result)    
end function

function f(b,c,d,t)
  if t < 20 then
    f = (b and c) or ((not b) and d)
  elseif t < 40 then
    f = b xor c xor d
  elseif t < 60 then
    f = (b and c) or (b and d) or (c and d)
  else
    f = b xor c xor d
  end if
end function

function k(t)
  if t < 20 then
    k = clng(1518500249)
  elseif t < 40 then
    k = clng(1859775393)
  elseif t < 60 then
    k = clng(-1894007588)
  else
    k = clng(-899497514)
  end if
end function

function pad(message)
  dim l, n
  l = len(message)
  n = (((l+8) \ 64) + 1)*16
  redim m(n-1)
  for i = 0 to n-1
    m(i) = clng(0)
  next
  for i = 0 to l-1
    m(i\4) = m(i\4) or lshift(asc(mid(message,i+1,1)),(24-(i mod 4)*8))
  next
  m(l\4) = m(l\4) or lshift(clng(128),(24-(l mod 4)*8))
  m(n-1) = l*8
  pad = m
end function

function sha1(message)
  dim h0, h1, h2, h3, h4
  dim a, b, c, d, e, temp
  dim l, n
  dim w(79)
  
  l = len(message)
  n = (((l+8) \ 64) + 1)*16
  m = pad(message)
  
  h0 = clng(1732584193)
  h1 = clng(-271733879)
  h2 = clng(-1732584194)
  h3 = clng(271733878)
  h4 = clng(-1009589776)
  
  for block = 0 to n-1 step 16
    a = h0
    b = h1
    c = h2
    d = h3
    e = h4
    for t = 0 to 79
      if t < 16 then
        w(t) = m(block + t)
      else
        w(t) = rol(w(t-3) xor w(t-8) xor w(t-14) xor w(t-16),1)
      end if
      temp = add32(rol(a,5),add32(f(b,c,d,t),add32(e,add32(w(t),k(t)))))
      e = d
      d = c
      c = rol(b,30)
      b = a
      a = temp
    next
    h0 = add32(h0, a)
    h1 = add32(h1, b)
    h2 = add32(h2, c)
    h3 = add32(h3, d)
    h4 = add32(h4, e)
  next
  sha1 = tohex(h0)+tohex(h1)+tohex(h2)+tohex(h3)+tohex(h4)
end function
%>

keywords: SHA-1 sha-1 SHA1 sha1 sha fips 180-1