(AutoIt) 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.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

; 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...

Local $bSuccess

; -----------------------------------------------------------------
; (Client-Side) Generate an ECC key, save the public part to a file.
; -----------------------------------------------------------------
$oPrngClient = ObjCreate("Chilkat.Prng")
$oEccClient = ObjCreate("Chilkat.Ecc")
Local $oPrivKeyClient = $oEccClient.GenEccKey("secp256r1",$oPrngClient)
If ($oEccClient.LastMethodSuccess <> True) Then
    ConsoleWrite($oEccClient.LastErrorText & @CRLF)
    Exit
EndIf

Local $oPubKeyClient = $oPrivKeyClient.GetPublicKey()
$oPubKeyClient.SavePemFile(False,"qa_output/eccClientPub.pem")

; -----------------------------------------------------------------
; (Server-Side) Generate an ECC key, save the public part to a file.
; -----------------------------------------------------------------
$oPrngServer = ObjCreate("Chilkat.Prng")
$oEccServer = ObjCreate("Chilkat.Ecc")
Local $oPrivKeyServer = $oEccServer.GenEccKey("secp256r1",$oPrngServer)
If ($oEccServer.LastMethodSuccess <> True) Then
    ConsoleWrite($oEccServer.LastErrorText & @CRLF)
    Exit
EndIf

Local $oPubKeyServer = $oPrivKeyServer.GetPublicKey()
$oPubKeyServer.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.
$oPubKeyFromServer = ObjCreate("Chilkat.PublicKey")
$oPubKeyFromServer.LoadFromFile("qa_output/eccServerPub.pem")
Local $sharedSecret1 = $oEccClient.SharedSecretENC($oPrivKeyClient,$oPubKeyFromServer,"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.
$oPubKeyFromClient = ObjCreate("Chilkat.PublicKey")
$oPubKeyFromClient.LoadFromFile("qa_output/eccClientPub.pem")
Local $sharedSecret2 = $oEccServer.SharedSecretENC($oPrivKeyServer,$oPubKeyFromClient,"base64")

; ---------------------------------------------------------
; Examine the shared secrets.  They should be the same.
; Both sides now have a secret that only they know.
; ---------------------------------------------------------
ConsoleWrite($sharedSecret1 & @CRLF)
ConsoleWrite($sharedSecret2 & @CRLF)