(Classic ASP) Hash a Hex String

Demonstrates common pitfalls in hashing a hex string..

Note: This example requires Chilkat v9.5.0.70 or greater.

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ActiveX for 32-bit and 64-bit Windows

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<%
' This example assumes the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Crypt2")
set crypt = Server.CreateObject("Chilkat.Crypt2")

' We have a hex string to be SHA-256 hashed:  "b08538d832bf"
' The result we expect to receive is "8a9f04cb1adfbd7f59c5918635f92f6c847e5b15f9828519d2fdbd6ead0918fc"

strToHash = "b08538d832bf"

' How do we get this result?

' The 1st question to be answered is:  What bytes are getting hashed?  
' There are two possibilities:
' 1) Hash 12 bytes, namely the us-ascii values for 'b', '0', '8', '5', .... 'b', 'f'
' or
' 2) Hash 6 bytes:  0xb0, 0x85, ... 0xbf
' 

' This is how to hash the 12 us-ascii byte values:
' The Charset property defines the byte representation of the string passed to the hash algorithm:
crypt.Charset = "us-ascii"
' The EncodingMode property defines the binary encoding (hex, base64, etc.) of the hash returned as an encoded string.
crypt.EncodingMode = "hex"
crypt.HashAlgorithm = "sha256"

hashValue = crypt.HashStringENC(strToHash)
Response.Write "<pre>" & Server.HTMLEncode( crypt.LastErrorText) & "</pre>"
Response.Write "<pre>" & Server.HTMLEncode( "hash of 12 us-ascii bytes: " & hashValue) & "</pre>"

' The result is:  327F2B33A0F0580D09840B0D7CEE54514CA33E9A  (not what we were hoping).

' -------------------------------------------
' This is how to hash the 6 bytes
' 
' "hex" is not an actual character encoding.  It's a special value to be used to tell Chilkat to hex decode
' the string and pass the decoded bytes to the hash algorithm...
' Note: This example requires Chilkat v9.5.0.70 or greater for the "hex" Charset to work properly.
crypt.Charset = "hex"
' The EncodingMode and HashAlgorithm remain the same..
hashValue = crypt.HashStringENC(strToHash)
Response.Write "<pre>" & Server.HTMLEncode( crypt.LastErrorText) & "</pre>"
Response.Write "<pre>" & Server.HTMLEncode( "hash of 6 hex bytes: " & hashValue) & "</pre>"

' The result is 8A9F04CB1ADFBD7F59C5918635F92F6C847E5B15F9828519D2FDBD6EAD0918FC (which equals the hash we were expecting)

%>
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