VBScript

Verify the RSA Signature of a SHA256 Hash

See more RSA Examples

Demonstrates how to verify an RSA signature of a SHA256 hash. VBScript

Dim fso, outFile
Set fso = CreateObject("Scripting.FileSystemObject")
'Create a Unicode (utf-16) output text file.
Set outFile = fso.CreateTextFile("output.txt", True, True)

success = 0

' This example assumes the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

' Let's say you have a file containing the 32-bytes of a SHA256 hash,
' and a file that is an RSA signature of those 32 bytes.
' Here's how you verify using the RSA public key found in a PEM.

set pubKey = CreateObject("Chilkat.PublicKey")
success = pubKey.LoadFromFile("rsaPubKey.pem")
If (success = 0) Then
    outFile.WriteLine(pubKey.LastErrorText)
    WScript.Quit
End If

set rsa = CreateObject("Chilkat.Rsa")

' Get the public key.
success = rsa.UsePublicKey(pubKey)
If (success = 0) Then
    outFile.WriteLine(rsa.LastErrorText)
    WScript.Quit
End If

' Get the 32-byte SHA256 hash.
set bdHash = CreateObject("Chilkat.BinData")
success = bdHash.LoadFile("myHash.sha256")
If (success = 0) Then
    outFile.WriteLine("Failed to load SHA256 hash.")
    WScript.Quit
End If

' Get the RSA signature to be validated.
set bdSig = CreateObject("Chilkat.BinData")
success = bdSig.LoadFile("mySig.sig")
If (success = 0) Then
    outFile.WriteLine("Failed to load RSA signature.")
    WScript.Quit
End If

' Verify the signature against the SHA256 hash.
enc = "base64"
rsa.EncodingMode = enc
success = rsa.VerifyHashENC(bdHash.GetEncoded(enc),"sha256",bdSig.GetEncoded(enc))
If (success = 0) Then
    outFile.WriteLine(rsa.LastErrorText)
    WScript.Quit
End If

outFile.WriteLine("Signature validated.")

outFile.Close