(Excel) 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 Chilkat.PrivateKey
Set privKey = Chilkat.NewPrivateKey

success = privKey.LoadEncryptedPemFile("qa_data/ecc/secp256r1-key-pkcs8-secret.pem","secret")
If (success = False) Then
    Debug.Print privKey.LastErrorText
    Exit Sub
End If

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

Dim ecdsa As Chilkat.Ecc
Set ecdsa = Chilkat.NewEcc
Dim prng As Chilkat.Prng
Set prng = Chilkat.NewPrng

' Sign the sha256 hash of the data.  Return the ECDSA signature in the base64 encoding.
Debug.Print "ECDSA signing the sha256 hash of the data..."

sig = ecdsa.SignBd(bd,"sha256","base64",privKey,prng)
Debug.Print "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 Chilkat.PublicKey
Set pubKey = Chilkat.NewPublicKey
success = pubKey.LoadFromFile("qa_data/ecc/secp256r1-pub.pem")
If (success = False) Then
    Debug.Print pubKey.LastErrorText
    Exit Sub
End If

Dim ecc2 As Chilkat.Ecc
Set ecc2 = Chilkat.NewEcc

result = ecc2.VerifyBd(bd,"sha256",sig,"base64",pubKey)
If (result <> 1) Then
    Debug.Print ecc2.LastErrorText
    Exit Sub
End If

Debug.Print "Verified!"

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

Debug.Print "--------------------------------------------"
Debug.Print "ECDSA signing the sha384 hash of the data..."

sig = ecdsa.SignBd(bd,"sha384","base64",privKey,prng)
Debug.Print "sig = "; sig

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

Debug.Print "Verified!"