(PureBasic) Ed25519 Key Exchange (Shared Secret)

Demonstrates how to create an Ed25519 shared secret for use in key exchange.

Note: This example requires Chilkat v9.5.0.83 or greater.

Chilkat PureBasic Module Download Chilkat PureBasic Module

IncludeFile "CkEdDSA.pb"
IncludeFile "CkPrivateKey.pb"
IncludeFile "CkPublicKey.pb"

Procedure ChilkatExample()

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

    ; Alice's private key, a:
    ;     77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a
    ; Alice's public key, X25519(a, 9):
    ;     8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4e6a
    ; Bob's private key, b:
    ;     5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb
    ; Bob's public key, X25519(b, 9):
    ;     de9edb7d7b7dc1b4d35b61c2ece435373f8343c85b78674dadfc7e146f882b4f
    ; Their shared secret, K:
    ;     4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742

    alicePrivKey.s = "77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a"
    bobPubKey.s = "de9edb7d7b7dc1b4d35b61c2ece435373f8343c85b78674dadfc7e146f882b4f"

    privKey.i = CkPrivateKey::ckCreate()
    If privKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; This example shows only one way of loading an Ed25519 private key.
    ; Chilkat can load other formats (JWK, PEM, ASN.1 DER, etc.)  
    ; You may do so by calling LoadAnyFormat or LoadAnyFormatFile.
    success.i = CkPrivateKey::ckLoadEd25519(privKey,alicePrivKey,"")
    If success = 0
        Debug CkPrivateKey::ckLastErrorText(privKey)
        CkPrivateKey::ckDispose(privKey)
        ProcedureReturn
    EndIf

    pubKey.i = CkPublicKey::ckCreate()
    If pubKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkPublicKey::ckLoadEd25519(pubKey,bobPubKey)
    If success = 0
        Debug CkPublicKey::ckLastErrorText(pubKey)
        CkPrivateKey::ckDispose(privKey)
        CkPublicKey::ckDispose(pubKey)
        ProcedureReturn
    EndIf

    ; Create the shared secret:
    eddsa.i = CkEdDSA::ckCreate()
    If eddsa.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    sharedSecret.s = CkEdDSA::ckSharedSecretENC(eddsa,privKey,pubKey,"hexlower")
    If CkEdDSA::ckLastMethodSuccess(eddsa) = 0
        Debug CkEdDSA::ckLastErrorText(eddsa)
        CkPrivateKey::ckDispose(privKey)
        CkPublicKey::ckDispose(pubKey)
        CkEdDSA::ckDispose(eddsa)
        ProcedureReturn
    EndIf

    Debug "Computed: " + sharedSecret
    Debug "Expected: 4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742"


    CkPrivateKey::ckDispose(privKey)
    CkPublicKey::ckDispose(pubKey)
    CkEdDSA::ckDispose(eddsa)


    ProcedureReturn
EndProcedure