(Perl) 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 Perl Downloads Perl Module for Windows, MacOS, Linux, Alpine Linux

use chilkat();

# 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 = chilkat::CkPrng->new();
$eccClient = chilkat::CkEcc->new();
$privKeyClient = chilkat::CkPrivateKey->new();
$success = $eccClient->GenKey("secp256r1",$prngClient,$privKeyClient);
if ($success == 0) {
    print $eccClient->lastErrorText() . "\r\n";
    exit;
}

$pubKeyClient = chilkat::CkPublicKey->new();
$privKeyClient->ToPublicKey($pubKeyClient);
$pubKeyClient->SavePemFile(0,"qa_output/eccClientPub.pem");

# -----------------------------------------------------------------
# (Server-Side) Generate an ECC key, save the public part to a file.
# -----------------------------------------------------------------
$prngServer = chilkat::CkPrng->new();
$eccServer = chilkat::CkEcc->new();
$privKeyServer = chilkat::CkPrivateKey->new();
$eccServer->GenKey("secp256r1",$prngServer,$privKeyServer);

$pubKeyServer = chilkat::CkPublicKey->new();
$privKeyServer->ToPublicKey($pubKeyServer);
$pubKeyServer->SavePemFile(0,"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 = chilkat::CkPublicKey->new();
$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 = chilkat::CkPublicKey->new();
$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.
# ---------------------------------------------------------
print $sharedSecret1 . "\r\n";
print $sharedSecret2 . "\r\n";