Re: [IPsec] New method to resist replay attack in ikev2

[Tero Kivinen <[e-mail]>]

ramaswamy writes:
> Thanks for the response, I agree with your comments, I think we can use
> certificates to avoid man in the middle attacks and error message flooding
> in the INIT phase only, as certificates are signed by trusted certificate
> authorities authenticity is ensured.
> 
> If certificates are used in INIT message exchanges [mutual authentication],
> we can effectively avoid afore said attacks as it avoids huge computation of
> IKE-keys before the client OR server is authenticated.

RSA operations are already huge computation. There is no big
difference whether you do RSA or Diffie-Hellman.

> To avoid Replay attacks:
> By using RSA private key of certificate to encrypt the nonce (Ni) in
> INIT_REQUEST message we can avoid replay attacks, at the receiving end,
> first certificate is verified using root CA and nonce is decrypted using
> public key of the received certificate which ensures that sender holds the
> valid private key of the certificate and not an attacker.  By using nonce we
> can avoid Replay attacks[Packets can be rejected if the same nonce is
> received within a particular session].

So you plan to store that nonce forever, and always verify that the
nonce is not used before? That would be extremely expensive way to
solve the replay attack.
-- 
[e-mail]