(Classic ASP) Example: Hash Text in Chunks

Shows how to generate a final hash, like SHA-256, for a large text by processing it in chunks.

Chilkat ActiveX Downloads

ActiveX for 32-bit and 64-bit Windows

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<%
set crypt = Server.CreateObject("Chilkat.Crypt2")
crypt.HashAlgorithm = "sha256"
crypt.Charset = "utf-8"

set bd = Server.CreateObject("Chilkat.BinData")

s = "The quick brown fox jumped over the lazy dog." & vbCrLf

' Accumulate the text in a StringBuilder.  We'll demonstrate hashing the text in chunks,
' and then also hashing the entire text at once to show the results are the same.

success = bd.AppendString(s,"utf-8")
success = crypt.HashBeginString(s)

i = 0
Do While i < 200
    success = bd.AppendString(s,"utf-8")
    success = crypt.HashMoreString(s)
    i = i + 1
Loop

' Get the hash in base64 format.
crypt.EncodingMode = "base64"

encodedHash = crypt.HashFinalENC()
Response.Write "<pre>" & Server.HTMLEncode( "Hash computed in chunks: " & encodedHash) & "</pre>"

' Let's alternatively compute the hash of the entire amount of data at once,
' to show the hash computation is the same:
encodedHash = crypt.HashBdENC(bd)
Response.Write "<pre>" & Server.HTMLEncode( "Hash computed in 1 step: " & encodedHash) & "</pre>"

' Output:

' Hash computed in chunks: unwkVff61k40roRIJizaknreScHaL6frWe37kydXbZQ=
' Hash computed in 1 step: unwkVff61k40roRIJizaknreScHaL6frWe37kydXbZQ=

%>
</body>
</html>