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IPsec can protect data flows between a pair of hosts (host-to-host), between a pair of security gateways (network-to-network), or between a security gateway and a host (network-to-host). [1] IPsec uses cryptographic security services to protect communications over Internet Protocol (IP) networks.
Negotiation of IPsec security association (SA), typically through Internet key exchange (IKE). This is carried out over UDP port 500, and commonly uses either a shared password (so-called " pre-shared keys "), public keys, or X.509 certificates on both ends, although other keying methods exist.
As a framework, [1] ISAKMP typically utilizes IKE for key exchange, although other methods have been implemented such as Kerberized Internet Negotiation of Keys. A Preliminary SA is formed using this protocol; later a fresh keying is done. ISAKMP defines procedures and packet formats to establish, negotiate, modify and delete Security Associations.
The Point-to-Point Tunneling Protocol (PPTP) is an obsolete method for implementing virtual private networks.PPTP has many well known security issues. PPTP uses a TCP control channel and a Generic Routing Encapsulation tunnel to encapsulate PPP packets.
Phase 1 operates in either Main Mode or Aggressive Mode. Main Mode protects the identity of the peers and the hash of the shared key by encrypting them; Aggressive Mode does not. [10] During IKE phase two, the IKE peers use the secure channel established in Phase 1 to negotiate Security Associations on behalf of other services like IPsec.
A security association (SA) is the establishment of shared security attributes between two network entities to support secure communication. An SA may include attributes such as: cryptographic algorithm and mode; traffic encryption key; and parameters for the network data to be passed over the connection.
IPsec NAT-T patches are also available for Windows 2000, Windows NT and Windows 98. [citation needed] NAT traversal and IPsec may be used to enable opportunistic encryption of traffic between systems. NAT traversal allows systems behind NATs to request and establish secure connections on demand.
A couple of new HAIPE devices will combine the functionality of a router and encryptor when HAIPE IS version 3.0 is approved. General Dynamics has completed its TACLANE version (KG-175R), which house both a red and a black Cisco router, and both ViaSat and L-3 Communications are coming out with a line of network encryptors at version 3.0 and above.