(VB.NET) ECDSA Sign and Verify Data using Different Hash Algorithms

Demonstrates how to create ECDSA signatures on data using different hash algorithms.

Note: This example requires Chilkat v9.5.0.85 or greater because the SignBd and VerifyBd methods were added in v9.5.0.85.

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

' First load an ECDSA private key to be used for signing.
Dim privKey As New Chilkat.PrivateKey
Dim success As Boolean = privKey.LoadEncryptedPemFile("qa_data/ecc/secp256r1-key-pkcs8-secret.pem","secret")
If (success = False) Then
    Debug.WriteLine(privKey.LastErrorText)
    Exit Sub
End If


' Load some data to be signed.
Dim bd As New Chilkat.BinData
success = bd.LoadFile("qa_data/hamlet.xml")
If (success = False) Then
    Debug.WriteLine("Failed to load file to be hashed.")
    Exit Sub
End If


Dim ecdsa As New Chilkat.Ecc
Dim prng As New Chilkat.Prng

' Sign the sha256 hash of the data.  Return the ECDSA signature in the base64 encoding.
Debug.WriteLine("ECDSA signing the sha256 hash of the data...")
Dim sig As String = ecdsa.SignBd(bd,"sha256","base64",privKey,prng)
Debug.WriteLine("sig = " & sig)

' Verify the signature against the original data.
' (We must use the same hash algorithm that was used when signing.)

' Load the public key that corresponds to the private key used for signing.
Dim pubKey As New Chilkat.PublicKey
success = pubKey.LoadFromFile("qa_data/ecc/secp256r1-pub.pem")
If (success = False) Then
    Debug.WriteLine(pubKey.LastErrorText)
    Exit Sub
End If


Dim ecc2 As New Chilkat.Ecc
Dim result As Integer = ecc2.VerifyBd(bd,"sha256",sig,"base64",pubKey)
If (result <> 1) Then
    Debug.WriteLine(ecc2.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("Verified!")

' ----------------------------------------------------------------------------------------
' Let's do the same thing, but with sha384 hashing...

Debug.WriteLine("--------------------------------------------")
Debug.WriteLine("ECDSA signing the sha384 hash of the data...")

sig = ecdsa.SignBd(bd,"sha384","base64",privKey,prng)
Debug.WriteLine("sig = " & sig)

result = ecc2.VerifyBd(bd,"sha384",sig,"base64",pubKey)
If (result <> 1) Then
    Debug.WriteLine(ecc2.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("Verified!")