Visual Basic 6.0

Verify the RSA Signature of a SHA256 Hash

See more RSA Examples

Demonstrates how to verify an RSA signature of a SHA256 hash. Visual Basic 6.0

Dim success As Long
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.

Dim pubKey As New PublicKey
success = pubKey.LoadFromFile("rsaPubKey.pem")
If (success = 0) Then
    Debug.Print pubKey.LastErrorText
    Exit Sub
End If

Dim rsa As New ChilkatRsa

' Get the public key.
success = rsa.UsePublicKey(pubKey)
If (success = 0) Then
    Debug.Print rsa.LastErrorText
    Exit Sub
End If

' Get the 32-byte SHA256 hash.
Dim bdHash As New ChilkatBinData
success = bdHash.LoadFile("myHash.sha256")
If (success = 0) Then
    Debug.Print "Failed to load SHA256 hash."
    Exit Sub
End If

' Get the RSA signature to be validated.
Dim bdSig As New ChilkatBinData
success = bdSig.LoadFile("mySig.sig")
If (success = 0) Then
    Debug.Print "Failed to load RSA signature."
    Exit Sub
End If

' Verify the signature against the SHA256 hash.
Dim enc As String
enc = "base64"
rsa.EncodingMode = enc
success = rsa.VerifyHashENC(bdHash.GetEncoded(enc),"sha256",bdSig.GetEncoded(enc))
If (success = 0) Then
    Debug.Print rsa.LastErrorText
    Exit Sub
End If

Debug.Print "Signature validated."