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Create ECSDA Signature using Raw r and s Format (not ASN.1)

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Demonstrates how to create an ECDSA signature using the raw r/s format.

ECDSA signatures have two equal sized parts, r and s. There are two common formats for encoding the signature:

(a) Concatenating the raw byte array of r and s
(b) Encoding both into a structured ASN.1 / DER sequence.

This example demonstrates how to create a signature that is a byte array of r and s concatenated.

Note: This example requires Chilkat v9.5.0.97 or greater.

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Dim success As Boolean
success = False

// 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.

Dim sb As New Chilkat.StringBuilder
success = sb.Append("The quick brown fox jumps over the lazy dog")
Dim hash As String
hash = sb.GetHash("sha256","base64","utf-8")

// Load the ECDSA key to be used for signing.
Dim privKey As New Chilkat.PrivateKey
success = privKey.LoadPemFile("qa_data/ecc/secp256r1-key-pkcs8.pem")
If (success <> True) Then
    System.DebugLog(privKey.LastErrorText)
    Return
End If

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

// Produce a signature that is not ASN.1, but is instead the concatenation
// of the raw r and s signature parts.
// This feature was added in Chilkat v9.5.0.97
ecdsa.AsnFormat = False

Dim ecdsaSigBase64 As String
ecdsaSigBase64 = ecdsa.SignHashENC(hash,"base64",privKey,prng)
If (ecdsa.LastMethodSuccess <> True) Then
    System.DebugLog(ecdsa.LastErrorText)
    Return
End If

System.DebugLog("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
    System.DebugLog(pubKey.LastErrorText)
    Return
End If

// Note: When verifying, Chilkat will auto-detect the format for both kinds of ECDSA signatures (ASN.1 or binary r+s)
Dim result As Int32
result = ecdsa.VerifyHashENC(hash,ecdsaSigBase64,"base64",pubKey)
If (result = 1) Then
    System.DebugLog("Signature is valid.")
    Return
End If

If (result = 0) Then
    System.DebugLog("Signature is invalid.")
    Return
End If

If (result < 0) Then
    System.DebugLog(ecdsa.LastErrorText)
    System.DebugLog("The VerifyHashENC method call failed.")
    Return
End If