(Xojo Plugin) How to Generate an Elliptic Curve Shared Secret

Demonstrates how to generate an ECC (Elliptic Curve Cryptography) shared secret. Imagine a cilent has one ECC private key, the server has another. A shared secret is computed by each side providing it's public key to the other. The private keys are kept private.

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

// This example includes both client-side and server-side code.
// Each code segment is marked as client-side or server-side.
// Imagine these segments are running on separate computers...

Dim success As Boolean

// -----------------------------------------------------------------
// (Client-Side) Generate an ECC key, save the public part to a file.
// -----------------------------------------------------------------
Dim prngClient As New Chilkat.Prng
Dim eccClient As New Chilkat.Ecc
Dim privKeyClient As Chilkat.PrivateKey
privKeyClient = eccClient.GenEccKey("secp256r1",prngClient)
If (eccClient.LastMethodSuccess <> True) Then
    System.DebugLog(eccClient.LastErrorText)
    Return
End If

Dim pubKeyClient As Chilkat.PublicKey
pubKeyClient = privKeyClient.GetPublicKey()
success = pubKeyClient.SavePemFile(False,"qa_output/eccClientPub.pem")

// -----------------------------------------------------------------
// (Server-Side) Generate an ECC key, save the public part to a file.
// -----------------------------------------------------------------
Dim prngServer As New Chilkat.Prng
Dim eccServer As New Chilkat.Ecc
Dim privKeyServer As Chilkat.PrivateKey
privKeyServer = eccServer.GenEccKey("secp256r1",prngServer)
If (eccServer.LastMethodSuccess <> True) Then
    System.DebugLog(eccServer.LastErrorText)
    Return
End If

Dim pubKeyServer As Chilkat.PublicKey
pubKeyServer = privKeyServer.GetPublicKey()
success = pubKeyServer.SavePemFile(False,"qa_output/eccServerPub.pem")

// -----------------------------------------------------------------
// (Client-Side) Generate the shared secret using our private key, and the other's public key.
// -----------------------------------------------------------------

// Imagine that the server sent the public key PEM to the client.
// (This is simulated by loading the server's public key from the file.
Dim pubKeyFromServer As New Chilkat.PublicKey
success = pubKeyFromServer.LoadFromFile("qa_output/eccServerPub.pem")
Dim sharedSecret1 As String
sharedSecret1 = eccClient.SharedSecretENC(privKeyClient,pubKeyFromServer,"base64")

// -----------------------------------------------------------------
// (Server-Side) Generate the shared secret using our private key, and the other's public key.
// -----------------------------------------------------------------

// Imagine that the client sent the public key PEM to the server.
// (This is simulated by loading the client's public key from the file.
Dim pubKeyFromClient As New Chilkat.PublicKey
success = pubKeyFromClient.LoadFromFile("qa_output/eccClientPub.pem")
Dim sharedSecret2 As String
sharedSecret2 = eccServer.SharedSecretENC(privKeyServer,pubKeyFromClient,"base64")

// ---------------------------------------------------------
// Examine the shared secrets.  They should be the same.
// Both sides now have a secret that only they know.
// ---------------------------------------------------------
System.DebugLog(sharedSecret1)
System.DebugLog(sharedSecret2)