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Eavesdropping Modification of packets in transit Identity spoofing (forged source IP addresses) Denial of service Many solutions are application-specific TLS for Web, S/MIME for email, SSH for remote login IPsec aims to provide a framework of open standards for secure communications over IP Protect every protocol running on top of IPv4 and IPv6
04/11/2017 Lecturer: Nguyễn Thị Thanh Vân – FIT - HCMUTE Introduction Applications of IPsec IPsec Architecture IPsec Protocol Suite o ESP, AH, IKE Packet Encapsulation in IPsec o Transport mode o Tunnel mode Internet Key Exchange (IKE) VPN IPsec 04/11/2017 04/11/2017 Eavesdropping Modification of packets in transit Identity spoofing (forged source IP addresses) Denial of service Many solutions are application-specific TLS for Web, S/MIME for email, SSH for remote login IPsec aims to provide a framework of open standards for secure communications over IP Protect every protocol running on top of IPv4 and IPv6 04/11/2017 04/11/2017 04/11/2017 04/11/2017 IP security (IPsec) is a capability add headers of IPv4 or IPv6) IPsec encompasses (includes) three functional areas: o Authentication: • makes use of the HMAC message authentication code • can be applied to the entire original IP packet (tunnel mode) or to all of the packet except for the IP header (transport mode) o Confidentiality: • is provided by an encryption format known as encapsulating security payload • Both tunnel and transport modes can be accommodated o key management: • IKE defines a number of techniques for.it 04/11/2017 04/11/2017 IPsec provides the capability to secure communications across a LAN, across private and public WANs, and across the Internet o Secure branch office connectivity over the Internet: saving costs and network management overhead o Secure remote access over the Internet: reduces the cost of toll charges for traveling employees and telecommuters o Establishing extranet and intranet connectivity with partners: ensuring authentication and confidentiality and providing a key exchange mechanism o Enhancing electronic commerce security: guarantees data is both encrypted and authenticate 04/11/2017 04/11/2017 04/11/2017 In a firewall or router, it provides strong security that can be applied to all traffic crossing the perimeter (edge) IPsec in a firewall is resistant to bypass if all traffic from the outside must use IP and the firewall is the only means of entrance from the Internet into the organization IPsec is below the transport layer (TCP, UDP) and so is transparent to applications IPsec can be transparent to end users IPsec can provide security for individual users 04/11/2017 IPsec provides security services at the IP layer by: o enabling a system to select required security protocols, o determining the algorithm(s) to use for the service(s), and o putting in place any cryptographic keys required to provide the requested services RFC 4301 lists the following services: o Access control o Connectionless integrity o Data origin authentication o Rejection of replayed packets (a form of partial sequence integrity) o Confidentiality (encryption) o Limited traffic flow confidentiality 04/11/2017 10 04/11/2017 Authentication Header (AH) protocol o For authenticating and securing data o IP protocol 51 Encapsulating Security Payload (ESP) protocol o For encrypting, authenticating, and securing data o IP protocol 50 Internet Key Exchange (IKE) protocol o For negotiating security parameters and establishing authenticated keys o Uses UDP port 500 for ISAKMP Authentication Header (AH) - RFC4302 o is an extension header o Provide data origin authentication for IP datagrams o provide connectionless integrity and o provide protection against replays 04/11/2017 12 04/11/2017 Encapsulating Security Payload (ESP) RFC4303 o consists of an encapsulating header and trailer used to provide encryption or combined encryption/authentication o ESP can be used to provide: • • • • • confidentiality, Data origin authentication, connectionless integrity, an anti-replay service (a form of partial sequence integrity), and (limited) traffic flow confidentiality o ESP can work with a variety of encryption and authentication algorithms 04/11/2017 13 AH and ESP support modes: transport and tunnel mode Transport mode: o o o o provides protection primarily for upper-layer protocols extends to the payload of an IP packet is used for end-to-end communication between to encrypt & optionally authenticate IP data • can traffic analysis but is efficient • good for ESP host-to-host traffic Tunnel mode: o o o o o o 04/11/2017 provides protection to the entire IP packet Packet travels through a tunnel from one point a IP network to another encrypts entire IP packet add new header for next hop no routers on way can examine inner IP header good for VPNs, gateway to gateway security 14 04/11/2017 04/11/2017 15 04/11/2017 16 04/11/2017 04/11/2017 17 04/11/2017 18 04/11/2017 04/11/2017 19 The two protocols AH and ESP can provide several security services for packets at the network layer as shown in the table below: 10 04/11/2017 To have two peers agree on a set of attributes for creating the IPsec security associations that could be used by ESP to encrypt the data To redo Diffie-Hellman (DH) exchange so that new keying material can be used to generate IPsec encryption keys Preshared keys Digital signatures Encrypted nonces 17 04/11/2017 18 04/11/2017 Data Encryption Standard (DES) Triple DES (3DES) 19 04/11/2017 - Cipher block: DES encryption algorithm converting fixed-length message into cipher text of same length -block size of DES is 64 bits while key length is 56 bits -Initialization vector is sent in ESP header Overall key length is 168 bits 20 04/11/2017 a security policy applied to each IP packet that transits from a source to a destination IPsec policy is determined primarily by the interaction of two databases: o the security association database (SAD) and o the security policy database (SPD) Security Associations Security Association Database Security Policy Database IP Traffic Processing 04/11/2017 41 04/11/2017 42 21 04/11/2017 a one-way logical connection between sender & receiver that affords security service to the traffic carried on it It is a mechanism that IPSec used to establish the security parameters between a sender and a particular receiver the first time they have communication Using SA, IPSec changes a connectionless protocol (IP) to a connection- oriented protocol SA is identified by parameters: o Security Parameters Index (SPI): A bit string assigned to this SA and having local significance only o IP Destination Address: address of the destination endpoint o Security Protocol Identifier: indicates whether the association is an AH or ESP security association 04/11/2017 43 SAD defines the parameters associated with each SA o Security Parameter Index o Sequence Number Counter o Sequence Counter Overflow o Anti-Replay Window o AH Information o ESP Information o Lifetime of this Security Association o IPsec Protocol Mode o Path MTU 04/11/2017 44 22 04/11/2017 SAD is needed to collect those of SAs It is a two-dimensional table with each row defining a single SA defined by a set of IP and upper-layer protocol field values, called selectors The following selectors determine an SPD entry: o Remote IP Address: (e.g., behind a firewall) o Local IP Address: (e.g., behind a firewall) o Next Layer Protocol: The IP protocol header (IPv4, IPv6, or IPv6 Extension) o Name: A user identifier from the operating o Local and Remote Ports: TCP or UDP port values 04/11/2017 46 23 04/11/2017 04/11/2017 47 04/11/2017 48 24 04/11/2017 combinations are: a AH in transport mode b ESP in transport mode c ESP followed by AH in transport mode (an ESP SA inside an AH SA) d Any one of a, b, or c inside an AH or ESP in tunnel mode 04/11/2017 49 This case illustrates simple VPN The tunnel could support AH, ESP, or ESP with the authentication option 04/11/2017 50 25 04/11/2017 provides either: o authentication, o confidentiality, or o both for all traffic between end systems 04/11/2017 51 support for a remote host that uses the Internet to reach an organization’s firewall and then to gain access to some server or workstation behind the firewall 04/11/2017 52 26 04/11/2017 LAN-to-LAN or site-to-site o Used to connect two private networks to form one combined virtual private network Remote-access client IPsec o Used to allow road warriors to be part of the trusted network 27 04/11/2017 Introduction Applications of Ipsec IPsec Architecture IPsec Protocol Suite o ESP, AH, IKE Packet Encapsulation in IPsec o Transport mode o Tunnel mode Internet Key Exchange (IKE) VPN IPsec 04/11/2017 56 28 04/11/2017 Experience o Set up VPN with IPSec • Client to Site • Site to site 04/11/2017 57 04/11/2017 58 29 04/11/2017 04/11/2017 59 04/11/2017 60 30 04/11/2017 04/11/2017 61 Cryptography and Network Security, Principles and Practice, William Stallings, Prentice Hall, Sixth Edition, 2013 o Chapter 19 o Others 04/11/2017 62 31 ... firewall 04/11/2017 52 26 04/11/2017 LAN-to-LAN or site-to-site o Used to connect two private networks to form one combined virtual private network Remote-access client IPsec o Used to allow... converting fixed-length message into cipher text of same length -block size of DES is 64 bits while key length is 56 bits -Initialization vector is sent in ESP header Overall key length is 168 bits 20... Diffie-Hellman exchange to thw art man-in-the-middle o attacks 04/11/2017 24 12 04/11/2017 Negotiates IPsec tunnel characteristics between two IPsec peers Negotiates IPsec protocol parameters