VB.NET

How to Generate an Elliptic Curve Shared Secret

See more ECC Examples

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. VB.NET

Dim success As Boolean = False

' 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.
' -----------------------------------------------------------------
Dim prngClient As New Chilkat.Prng
Dim eccClient As New Chilkat.Ecc
Dim privKeyClient As New Chilkat.PrivateKey
success = eccClient.GenKey("secp256r1",prngClient,privKeyClient)
If (success = False) Then
    Debug.WriteLine(eccClient.LastErrorText)
    Exit Sub
End If

Dim pubKeyClient As New 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.
' -----------------------------------------------------------------
Dim prngServer As New Chilkat.Prng
Dim eccServer As New Chilkat.Ecc
Dim privKeyServer As New Chilkat.PrivateKey
eccServer.GenKey("secp256r1",prngServer,privKeyServer)

Dim pubKeyServer As New 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.
Dim pubKeyFromServer As New Chilkat.PublicKey
pubKeyFromServer.LoadFromFile("qa_output/eccServerPub.pem")
Dim sharedSecret1 As String = 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
pubKeyFromClient.LoadFromFile("qa_output/eccClientPub.pem")
Dim sharedSecret2 As String = eccServer.SharedSecretENC(privKeyServer,pubKeyFromClient,"base64")

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