IP Security

1
IP Security
2
??

• ??
• IP AH
• IP ESP
• ????SA
• IPSec????????
• ??

3
????

• ???,??????????IPSec????
• ???,IPSec?????,01 BYTE, Jan. 2000, pp9499.
• ???????????????,IPSec????????????????,
  ??????,??????, June 1999, pp6885.
• Dave Kosiur, Building and Managing Virtual
  Private Networks, wiley computer publishing,
  1998.
• ???????,?????????, OREILLY, 1999?

4

• General IPSec RFCs 1825, 2401, 2411, 2521,
  2709, 2764
• ESP, AH RFCs 1826-187, 2402, 2406
• Key Exchange RFCs 2407-2409, 2412, 2367,
  2522-2523
• Cryptography RFCs 1828-1829,2085, 2104, 2202,
  2403-2405, 2410, 2451, 2393-2395
• Internet Rosurces
• http//www.ietf.org/thml.charters/ipsec-charter.ht
  ml
• http//firewall.sysware.com.tw/faq/vpn/ipsec.html
• http//firewall.sysware.com.tw/faq/vpn/SKIP.html
• http//conway.cba.ufl.edu/ism6222/Ipsec.html
• http//www.hsc.fr/veille/papier/papier.html.en
• http//www.ip-sec.com
• http//www.cisco.com/public/library/isakmp/ipsec.h
  tml

5
??

• IPSec??IETF????IP?????????
• ????1995???,??AH?ESP????,??????????????
• ????1998?11???,????AH?ESP?????,???????????????????
  ,?????????????????????

6
OSI Layer ? TCP/IP Layer
OSI 7 Layer
TCP/IP 5 Layer
7
????

• ???????????
• ??IP (IP Spoofing)
• ??????? (eavesdropping)
• ???? (Packet sniffing)

8
IPSec Architecture
9
IPSec???

• IETF(Internet Engineering Task Force)?????????????
  ????IPSec(IP Security),???????????,???????????????
  (Authentication)????(Integrity)?????(Access
  Control)?????(Confidentiality)??????
• IPv4?IPv6
• IPv4 ???(Optional)
• IPv6 ???(Mandatory)

10
IPSec???

• IPSec????????????????,????????????????????????????
  ????IPSec?,???????
• IPSec????????????,??????IPSec?IP????????IPSec?????
  ???

11

• ??IPSec?????????
• ?????(campus network)???????????
• ??Internet??????????
• ????Internet???????????(???????IPSec??,???IPSec
  ????????,??IP???????????????)
• IPSec??????????????????????????

12
????

• 1. SSL (Secure Socket Layer)
• ???????????????????,??????IP?????
• ???IPSec????????,??????????SSL?
• 2. PPTP (Point-to-Point Tunneling Protocol)
• ??????????,???????????
• ????IPSec???????,??????????

13

• 3. L2TP (Layer 2 Tunneling Protocol)
• ?????IP??
• ?????IPX,???????????????????????
• ??????????
• Microsoft????L2TP?IPSec,?L2TP?VPN?????????????????
  ?

14
IPSec vs SSL

• IPSec
• Network layer/IP
• Secure Host/Subnet-Host/Subnet
• No surgery on current applications
• Performance degraded for all application
• Sender authentication

• SSL
• Transport layer/Socket
• Secure Application - Application
• Applications have to be modified
• Applications do not use SSL do not suffer
  performance loss
• No sender authentication

15
IPSec
16
IPSec???

• ??IPSec?????????????????????????????

17

• IPSec??????????AH (Authentication Header)?ESP
  (Encapsulation Security Payload)??????????????????
  ???????????
• ????????????????????????????????,???SPI(Security
  Parameter Index)?????????????????????????????????
• ?????????????????,??????????(Tunnel
  Mode)?????(Transport Mode)???

18

• IP AH???????????,?????????IP ESP?????????,????ESP
  Header?????????????????????????
• IP AH?IP ESP????????????
• IPSec??IP AH?IP ESP????????????,???????SA(Security
  Association)?????IKE(Internet Key Exchange)?
• DOI(Domain of interpretation)????????????ISAKMP???
  Framework?

19
ESP protocol
AH protocol
Encryption algorithm
Authentication algorithm
DOI
Key management
IPSec architecture
20

• SKIP?ISAKMP/Oakley?????????ISAKMP/Oakley?SKIP???,?
  ????????,????IPv6????????

21
IPSec ??

• SAD Security Association Database
• SPD Security Policy Database

22
IP AH

• IP AH?????????????,?????????????????????,???????
• ?????????,??????????????????,?????????????????

23

• AH????128?????MD5(Message Digest
  5)?????????????(????SHA-1(Secure Hash Algorithm
  1)),?????(??????)?????,???????????????????????
• ?????,????????
• ??IPSec??,IPv6????????????128???MD5,???IPv4???????
  ??AH???

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• AH??

25

• ????
• ????(8 bits)??AH???????
• ??(8 bits)??????????
• ??(16 bits) ?????????
• SPI(Security Parameter Index, 32 bits)
• ????????????????????????????????
• ?????????????(??AH ??)????????????SA(Security
  Association)

26

• ??(32 bits)
• ???????
• ?????????????????,????????
• ????(Authentication Data)
• ?????(IPv4?32??????, IPv6?64??????)???
• ?????????ICV(Integrity Check Value)??????(Padding)
  
• ????????????????????(SPI??)??(MD5?SHA-1)

27
HMAC-MD5?HMAC-SHA-1

• ????,SHA-1?????MD5???hash function
• HMAC(Hashed Message Authentication
  Code)????secret key???hash function????MAC(message
  authentication code)?HMAC?????hash
  function???????,????????hash function???,?????????
  ?

28
HMAC-MD5?HMAC-SHA-1(contd)

• HMAC-MD5????128 bits,?HMAC-SHA-1?160 bits
• ?authenticator length?????96 bit,????????,??Hash
  function?Hash??????????(truncated)

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AH????

• 1. IPv4

Before applying AH
Original IP header (any options)
IPv4
TCP
Data
After applying AH
Original IP header (any options)
AH
TCP
Data
IPv4
Authenticated except for mutable fields
Original IP header (any options)
New IP header (any options)
TCP
Data
AH
IPv4
Authenticated except for mutable fields in the
new IP header
30
???????
31

• 2. IPv6

Before applying AH
Original IP header
Extra headers if present
TCP
Data
IPv6
After applying AH
Hop-by-hop, destination, routing, fragment
Original IP header
Destination options
TCP
Data
AH
IPv6
Authenticated except for mutable fields
Ext headers If present
New IP header
Ext headers if present
Original IP header
AH
TCP
Data
IPv6
Authenticated except for mutable fields in the
new IP header
32
IP ESP

• IP ESP????????IP?????(Payload),??????????IP
  Datagram??????TCP, UDP?ICMP??(????????????????)?
• (Note ICMP(Internet Control Protocol)???????????
  ????????????)
• IP ESP?????????DES??Triple-DES,????CBC (Cipher
  Block Chain)
• IP ESP???????????,?????????

33

• ESP?????

34

• IP ESP????????????????
• ?????????Security Gateway??????????
• ???????????,?????IP??,????????

35

• ESP??
• ESP?????ESP Header?ESP Trailer????

36

• ????
• SPI?Sequence Number ?AH???
• Payload Data ESP?????????,?????
• (1)???IP???????
• (2)IP????????????
• ????????(Tunnel Mode),????????(Transport Mode)
• ??????SPI??????????????????

37

• ??????
• ??????????????????,?AH??(AH???IP??????????)
• ???????,?SPI??

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• 1. ESP????

Before applying ESP
Original IP header (any options)
IPv4
TCP
Data
After applying ESP
Original IP header (any options)
ESP trailer
ESP authorization
ESP header
Ipv4
TCP
Data
Encrypted
Authenticated
39
Before applying ESP
Original IP header
Extra headers if present
TCP
Data
IPv6
After applying ESP
Hop-by-hop, destination, routing, fragment
Original IP header
ESP trailer
Destination options
ESP authorization
ESP
TCP
Data
IPv6
Encrypted
Authenticated
40

• ESP?????????????
• ?????????,??IP??????,??????,???????IP??

41

• ??
• (1) ??ESP?IP Payload????
• (2) ???
• (i) ????? ID ?????????SA ??
• (ii) ??????(DES?Triple-DES)?? ?????
• (3) ??? (i) ??ESP??????????IP??
• (ii) ?ESP Header??SPI??????? SA
• (iii) ??SA????????????? ???????

42

• ???????,???????????????
• ??Firewall, Gateway Proxy??,??????????,???????????
  ??

43

• 2. ESP????

Original IP header (any options)
New IP header (any options)
ESP authorization
ESP trailer
Data
IPv4
ESP
TCP
Encrypted
Authenticated
IPv6
Original IP header
New IP header
New ext headers
Original ext header
ESP trailer
ESP authorization
ESP
TCP
Data
Encrypted
Authenticated
44

• ??
• (1) ???
• (i) ???SA??????IP?????
• (ii) ?????ESP Header
• (iii) Prepend??IP??
• (2) ??? (i) ??ESP Herder????SPI???SA
• (ii) ??ESP Herder??????,???
  ?????IP?????

45
AH?ESP????

• IP AH?IP ESP?????????
• 1. ??????

??
????
??
??
????
??
46

• 2. ??????

??
??
47
????SA

• ??????????SPI?????,?????(AH?ESP)?????
• SA (Security Association)??????????,??????????IP
  ???????,????????,????
• ????????????????
• ????????????DES?Triple-DES,????MD5?SHA-1
• ????????
• SA?????

48

• SA???SPI(32 bits)???,?????SPI????????SA??
• ??A??????B SPI??1000,?????SA??,?????????,?DES,???0
  x1234567890abcdef(???64??)?
• ????A?????SPI 1000????????????????B?
• ?B?????????A?SPI????????SA?????????

49

• SA????(?A?B),???A???B???????????????,?????SA?((A?B
  )?(B?A))
• SA???????
• (1) ????????(Host-Oriented Keying)
• ??????,????????????,?
• ???????
• (2) ?????????(User-Oriented Keying)
• ???????,???????????

50

• ??IPSec?????

51

• ???CHECK POINT Firewall-1???

?????
?????
ESP AH????
????
????
52
IPSec????????

• ??IPSec???????????????????????????
• ??????????????????????
• ????????????????SKIP(Simple Key-management for
  IP)?ISAKMP/Oakley(Internet Security Association
  Key Management Protocol/Oakley)??,????????????????
  ?SKIP????,?ISAKMP/Oakley???????????

53

• 1. SKIP
• SKIP??Sun Microsystem???
• ?????????????
• ????????????Kij(????Diffie Hellman????????????)

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Diffie Hellman PKDS
A
B
55
????Kij
Kij
Kij
??
??
KijnMD5(Kij/n)
KijnMD5(Kij/n)
Kp
?Kijn?Kp????? SKIP Header????
?Kijn??Kp
Kp
Kp
E_KpMD5(Kp/0)
A_KpMD5(Kp/2)
E_KpMD5(Kp/0)
A_KpMD5(Kp/2)
????
????
????
????
56

• ????
• Kij???????????
• n?1995?1?1??????
• Kijn????,??1??????
• Kp????,??2??????
• E_Kp????
• A_Kp????

57

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rotocol
SKIP

SKIP

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Triple
-
DES

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DES

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MD5

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AH

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SPI
0x1234

Message Digest
?

IP

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??
protocol

TCP

IP

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(
IP

Payload)


SKIP????
58

• 2. ISAKMP/Oakley(IKE)
• ??????????,IETF??????????????Internet Key
  Exchange(IKE),???????
• ISAKMP
• ????????????IP????????????????
• ???????????????????
• ?????????????DOI(Domain of Interpretation)???

59

• OAKLEY
• ?????Deffie-Hellman?????????????
• ????IPSec???????????
• ??????????????????????,?????????????????????
• IKE
• IKE?IETF???????????
• ????????OAKLEY????????,???ISAKMP??????????????????
  ????

60

• DOI?IPSec DOI
• DOI??????????
• IPSec DOI?IETF?????????????

61
ISAKMP?2?Phase

• IKE???2?phase,??ISAKMP??????
• Phase 1 ????????????????ISAKMP SA
• Phase 2???????(negotiate)??????????(general-purpo
  se)?(???)SA (?????????SA)

62
Oakley???Mode

• Oakley??3?Mode???ISAKMP SA
• Main mode
• ???ISAKMP phase 1???
• Aggressive mode
• ?????ISAKMP phase 1???
• ??????
• ???(identity)???
• Quick mode
• ??ISAKMP phase 2???

63
ISAKMP Main mode

• ???????????ISAKMP SA
• ???????Key???ISAKMP SA
• ??3?two-way exchange

64
Main mode??
Initiator
Responder
65
Main mode?3?exchange

• ?Main mode???,??3?exchange
• (1) ??? SA ??
• ?????????hash function
• (2) ????
• ??Diffee-Hellman???????
• ?????Nonce (?????,??????????????)
• (3) SA???
• ??????,????

66
ISAKMP Aggressive mode

• ????Main mode?
• ????Main mode?
• ?????,?????????

67
Aggressive mode??
Initiator
Responder
68
ISAKMP Quick mode

• ???????????ISAKMP SA
• ???????Keying material
• ?Quick mode????????????????

69
Quick mode ??
Initiator
Responder
Hash1 H(Noncei SAKeyIDui/IDur) Hash2
H(NonceiNoncerSAKeyIDui/IDur) Has
h3 H(NonceiNoncer)
70
Quick mode?Key Generation

• Key?????????
• Non-perfect forward secrecy
• Perfect forward secrecy?????SA????Diffie-Hellman
  ?????

71
IPSec?VPN?????

• IPSec?????gateway????,?????
• ?IPSec??gateway?,???????Internet??????????
• ?????,?????????????

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(a)Gateway?Gateway
????
IPSec
IPSec
????
(b)???Gateway
IPSec
IPSec
(c) ?????
????
IPSec
IPSec
73
Leading Figures

• ??????? (Infrastructure)
• CISCO
• router
• ????
• Microsoft
• VPN in Windows operating system
• Linux
• IPv6/IPSec
• ????? (Service provider)
• MCI VPN service provider
• ?????? (Standard organization)
• IETF IPSec workgroup
• Steering the development of IPSec

74
The Comparison of computational cost
75
??

• IKE??????????????-???PKI??????????????????????????
  ??????????????????
• ????X.509????????(Public Key Infrastructure
  X.509, PKIX)???,?X.509????????????,??????????????
• ????IPSec??????????????X.509???????????Lotus?Cisc
  o?Entrust??????????PKI?

76

• ?????????????IPSec????????????,???????????????????
  ,???????????????
• ??????????????????,??????????IETF???????????????
  ?(Policy Exchange Resolution Protocol)?????????
• ??????????????IPSec???????????

77

• ????IPSec??IP???????????????,???????????,????????
  ??
• ????IPSec,IP????????????????????????????,??IPSec??
  ??????