IP (IPSec) 13 Network Security, Principles and Practice,2nd Ed. # $ !" : http://www.fata.ir http://mehr.sharif.edu/~shahriari IPSec IPSec (SA) AH ESP SA ! " # $" TCP/IP & ' - IPV4 Sharif Network Security Center (+, " #)( . ( , & " ) * . / : PGP S/MIME ) 12 "- " 0 : Kerberos 4 (0 " 3 ( : SSL IP 56 IP * 2 * & 3 " ;, ( & ,7 8 9 : < # ).# / 3 " " = 9 $" ,> > .( " ? IPSec D ,# * : = 9 ( *( ( .$ E "* ( $" 0 ) ( A#) $" 7 , IPSec < ,8 @ A# +B < : 8 , 7 IPSec J ( " , F G & + & 3 H$ I A: VPN ( F G & .A: " :+ "0 ( + & > 0 0 @ A# + . # )' ) 8 ( ( " J K +( B (,E (3 . IPSec Sharif Network Security Center IPSec & *( L 2 . J ,N ( LAN M K )K ( 0 ,? ( Firewall) O L ( < @ ( 81 1 0 # < P ; + " Q & 9 L: #R R ( " ( & 9 L: )K ( M K & + & + " " 0 0 @ A# ( < 2S :IPSec < 2S ).T A H N,# ( K IPv6 ( 1 : &( , 09 2 ( (Header) B ( IPSec ).# / (,: & IPv4 ( *( / IP $N : B * : & 9 ,# ( & J ,N *(, = IPSec J Architecture 8 1 : (ESP) Encapsulating Security Payload ( K J ,N , & ) , U IT# : (AH) Authentication Header $" 0 ( A# : $" : , 81 = ,8 :IPSec < < V + . 0 IPSec : * : V P&R $" < ,8 W <$.# / # "4I ( " Connectionless @ A# ( *( ( # 0 X# (Data Origin) *( ( A , & Replay ) < B ( * : * ( U IT# (Attack 8 7 39 #+ E 8 7 :IPSec Sharif Network Security Center ( & :IPSec Association Security P,<L 3 (Security Association) :H # 6 3 *(, IP 8 7 , & <1 . ( $" . " ( * 2 * 90 9 G 3 TCP ( Connection ( ;, IP ( SA :IPSec Association Security : : ! " #$ %3 SA : 3 :(SPI) Security Parameters Index SA * : *( ( A SA < Y Z (B : IP Destination Address AH SA F$ # 8 : Security Protocol Identifier ESP :IPSec Association Security SA Sequence Number Counter Sequence Counter Overflow Anti Replay Windows AH Information ESP Information SA Lifetime IPSec Protocol Mode Maximum Transmission Unit :IPSec < ( ESP AH :( ( (,E ( (Transport Mode) IP B [# + W( 2 J ,N ,7 <#J [# (Tunnel Mode) ) ,# +( 9 (Payload+ B )IP )" J E [# ; 3 +, ; ( :IPSec < 9 "/ 12 " )' (end-to-end) < *( L Payload ( B * :4I K) < : , ( < ^) Payload ? ( " ( (,: 8 1 : ESP , : AH : :IPSec ) ,# Gateway $K ( B U IT# Gateway @ A# (? ( *( L (router) 4 (, _ Functionality of Modes Sharif Network Security Center Authentication Header (AH) Authentication Header IP MAC & *( L , & *( ( # # 0 X# 0 # HMAC-SHA-1-96 HMAC-MD5-96 (+ ` T $" 3 F9 ,# & 09 G Authentication Header Sharif Network Security Center AH : AH ( (,E, B b, : ( 8)Next Header AH ,G 8 : ( 8)PayLoad Length * B *( L * : & : ( 16)Reserved SA @, SPI 0 # : ( 32)Sec. Param. Index * : : ( 32)Sequence Number ICV MAC * 2 ( : ( [ )Authentication Data $9 AH MAC A 7 ( 32 # 3 ) HMAC = ,8 96 e 9 f / ,G E K 96 0 HMAC-SHA-1 HMAC-MD5 ( 2 MAC A 7 ( W(TTL $ & 2,$E <E) P ,7 AH [ ) " [# & ( B WIP [ (R " B . ,: 2 * ) K( MAC A 7 ( 1 * MAC A 7 B & < ? ,Q LN 9 < (B (IP ) E AH : AH ( ) ,# #, i " 0 = OL : (Transport) 12 " , & "0 , & < " : (Tunnel)) ,# firewall) End-to-end versus End-toIntermediate Authentication Sharif Network Security Center Scope of AH Authentication Before Application IP payload is TCP segment (data unit) Sharif Network Security Center Scope of AH Authentication Transport Mode IPv6: AH is end-to-end payload Sharif Network Security Center Scope of AH Authentication Tunnel Mode Sharif Network Security Center AH (Replay) .# $ SA LN * 9 SA 0 " E & 32 E SA 3 & W 2 -1 (,: *( E $" Q & * : W (=64) 1 * :0 2 1 # * * * $ j :3 kYK * : f 19 * : 2 ( " *( L /3 09 2 Q ( / A : E AH * , K " # J ,N ( * ,G / ( m W * +B , & / ( E ( ,K P1 . * / *( 7 )K ( E K +(& n; MAC A 7 ( )* /( 7 & M K / L: , # W MAC A 7 (+T * / A m P ; * / *( 7 & M K E !(,: K ( ESP < 2S 39 # 8 7 # *( ( 8 7 & A T/ (AH T ) : , & *( L + . ,3-DES & *( L + . )CBC ( DES = ,8 & *( L (,E 1 Blowfish CAST ,3-IDEA ,IDEA ,RC5 (( ( ESP ESP SA : : SPI : : Sequence Number AH (,: 1 " , 7 : Payload 9 ^ < : Padding R $ 9 ,G : Pad Length Payload Data ( (,E, *( ( b, : Next Header Q ( + ) * : A 7 MAC : Authentication Data ( $ 9 (,K 0 9 2 T .# $ & 2,$E $9 * Encapsulating Security Payload Sharif Network Security Center ESP host 0 8 7 0 X# J ,N ( MAC + : 9 ^ ESP A ( W*( ( 81 q A D ,# : , 4I B & *( L Router D ,# 0 # ( * T 1 ") $N P[/* ? 1 T2 Y D ,# IP B +( " 3> 39 #1 B+. Transport Mode ESP used for communication between hosts scope Sharif Network Security Center ESP ) ,# * 9 E K ( MAC @, *& ( Y q A Z (B + : 9 ^ ? ESP A ( ESP B W* 2 ( : , )& J ,N E Z (B & Router ( P IP Z (B & Y .A: 9 + < * 2 # $A? VPN ( <: & . IPSec ) ,# Tunnel Mode ESP Sharif Network Security Center SA ! " # ESP AH & . < # SA . E,# & *( L W *( " & *( / ( "!" #= <B < ( H$ I m <A " # host D ,# IPSec & *( / gateway D ,# IPSec & *( / R (!" # Sharif Network Security Center Sharif Network Security Center Sharif Network Security Center Sharif Network Security Center $" ESP 3 # ( AH # (W $" 4 , ; $" 0 &,# ,# .= & ( <E ( () .= & $" P1 . $" ) ? 3>," = ( <#: ( $" *( L : "(,K IPSec $" &,# .(,: * e 9 f / 3 # ,# ).# / ISAKMP/Oakley n6N Internet Security Association and Key Management Protocol $" () : r ISAKMP/Oakley P Diffie- ).# / 9 r G $ "(,K $" ,# P 9 : Oakley $" 0 # ).# / *( " r G +B <L ^ " Hellman .(,: H$# ? :Clogging Attack 0 ).T Cookie + , ; 7# ,<L H # & *( L " . " $ (ISAKMP) SA rs [# W* " s W Man-In-The-Middle-Attack Replay Attack .# $ Nonce & *( L ( SA ? $" ! ? ).# / H # &9
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