(VB.NET) ECDSA Sign Data and Verify Signature

Demonstrates using the Elliptic Curve Digital Signature Algorithm to hash data and sign it. Also demonstrates how to verify the ECDSA signature.

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

' To create an ECDSA signature, the data first needs to be hashed.  Then the hash
' is signed.

' Use Chilkat Crypt2 to generate a hash for any of the following
' hash algorithms: SHA256, SHA384, SHA512, SHA1, MD5, MD2, HAVAL, RIPEMD128/160/256/320

Dim crypt As New Chilkat.Crypt2
crypt.HashAlgorithm = "SHA256"
crypt.Charset = "utf-8"
crypt.EncodingMode = "base64"

' Hash a string.
Dim hash1 As String = crypt.HashStringENC("The quick brown fox jumps over the lazy dog")
Debug.WriteLine("hash1 = " & hash1)

' Or hash a file..
Dim hash2 As String = crypt.HashFileENC("qa_data/hamlet.xml")
Debug.WriteLine("hash2 = " & hash2)

' (The Crypt2 API provides many other ways to hash data..)

' -----------------------------------------------------------
' An ECDSA private key is used for signing.  The public key is for signature verification.
' Load our ECC private key.
' Our private key file contains this:

' 	// -----BEGIN PRIVATE KEY-----
' 	MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQg3J8q/24D1sEKGdP9
' 	72MGYElLGpw/a56Y3t6pfON3uhShRANCAATlSmoizyhAwoYZAOuFBATl07/1RR54
' 	a1Dzfm16grxJe666AGKR+bSs24hk7TEpaeCTvT8YOOM3l+xKFg7zq6Q9
' 	-----END PRIVATE KEY-----

Dim privKey As New Chilkat.PrivateKey
Dim success As Boolean = privKey.LoadPemFile("qa_data/ecc/secp256r1-key-pkcs8.pem")
If (success <> True) Then
    Debug.WriteLine(privKey.LastErrorText)
    Exit Sub
End If


' We'll need a PRNG source for random number generation.
' Use Chilkat's PRNG (for the Fortuna PRNG algorithm).
Dim prng As New Chilkat.Prng

' Sign the hash..
Dim ecdsa As New Chilkat.Ecc
Dim ecdsaSigBase64 As String = ecdsa.SignHashENC(hash1,"base64",privKey,prng)
If (ecdsa.LastMethodSuccess <> True) Then
    Debug.WriteLine(ecdsa.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("ECDSA signature = " & ecdsaSigBase64)

' -----------------------------------------------------------
' Now let's verify the signature using the public key.

Dim pubKey As New Chilkat.PublicKey
success = pubKey.LoadFromFile("qa_data/ecc/secp256r1-pubkey.pem")
If (success <> True) Then
    Debug.WriteLine(pubKey.LastErrorText)
    Exit Sub
End If


Dim result As Integer = ecdsa.VerifyHashENC(hash1,ecdsaSigBase64,"base64",pubKey)
If (result = 1) Then
    Debug.WriteLine("Signature is valid.")
    Exit Sub
End If

If (result = 0) Then
    Debug.WriteLine("Signature is invalid.")
    Exit Sub
End If

If (result < 0) Then
    Debug.WriteLine(ecdsa.LastErrorText)
    Debug.WriteLine("The VerifyHashENC method call failed.")
    Exit Sub
End If