(PowerShell) 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.

Note: This example requires Chilkat v11.0.0 or greater.

Chilkat .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-x64\ChilkatDotNet47.dll"

# 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...

# -----------------------------------------------------------------
# (Client-Side) Generate an ECC key, save the public part to a file.
# -----------------------------------------------------------------
$prngClient = New-Object Chilkat.Prng
$eccClient = New-Object Chilkat.Ecc
$privKeyClient = New-Object Chilkat.PrivateKey
$success = $eccClient.GenKey("secp256r1",$prngClient,$privKeyClient)
if ($success -eq $false) {
    $($eccClient.LastErrorText)
    exit
}

$pubKeyClient = New-Object Chilkat.PublicKey
$privKeyClient.ToPublicKey($pubKeyClient)
$pubKeyClient.SavePemFile($false,"qa_output/eccClientPub.pem")

# -----------------------------------------------------------------
# (Server-Side) Generate an ECC key, save the public part to a file.
# -----------------------------------------------------------------
$prngServer = New-Object Chilkat.Prng
$eccServer = New-Object Chilkat.Ecc
$privKeyServer = New-Object Chilkat.PrivateKey
$eccServer.GenKey("secp256r1",$prngServer,$privKeyServer)

$pubKeyServer = New-Object Chilkat.PublicKey
$privKeyServer.ToPublicKey($pubKeyServer)
$pubKeyServer.SavePemFile($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.
$pubKeyFromServer = New-Object Chilkat.PublicKey
$pubKeyFromServer.LoadFromFile("qa_output/eccServerPub.pem")
$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.
$pubKeyFromClient = New-Object Chilkat.PublicKey
$pubKeyFromClient.LoadFromFile("qa_output/eccClientPub.pem")
$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.
# ---------------------------------------------------------
$($sharedSecret1)
$($sharedSecret2)