??? Yiter

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???????
??? Yiter itchen_at_kmu.edu.tw
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?????

• ????- ????? ????,????????
• ??????, ??????????????
• ???????
• Autorun.inf
• xxx.exe (????, ???, ??)
• Kavo_Killer.exe ??
• WowUSBProtector ??
• ???????? autorun.inf ????
• ??????
• http//wiki.kmu.edu.tw/index.php/Kavo_??

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Kavo Killer
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Wow USB protector
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?????? XP Professional

• Windows XP Professional
• ?? ? ?? ? ?? gpedit.msc (Windows XP Home Edition
  ??????)? ??
• ?? "????" ??, ????? ???? ? ?????? ? ??
• ??????? ? ?????? ??????
• ?? "????????" ???, ?? "???"
• ???? "???????" ?????, ?? "????"
• ??,?????????????

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?????? XP Home

• Windows XP Home (??? Windiws 2000)
• ?? ?? ? ?? ? ?? regedit
• ???????? HKEY_CURRENT_USER\SOFTWARE\Microsoft\Wind
  ows\CurrentVersion\Policies\Explorer\NoDriveTypeAu
  toRun
• ???? ????? 255,??? 255 (????????? autorun , ???
  95 ??)
• ???

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?????? XP Home
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Outline(1/2)

• ?????
• ????????
• ?????
• ?????(Substitution, Transposition, DES)
• ??????(Advanced Encryption Standard, AES)
• ??????(RSA)
• MAC
• ????

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Outline(2/2)

• ???(Firewall)
• ????????
• Packet Filtering
• Application Gateway
• Proxy Server
• Screened Host Firewall

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????????????
pw????
pw????
Sniffer, WireShark
pw????
eavesdropper
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????????

• Sniffer http//www.netscout.com
• Wireshark http//www.wireshark.org
• http//zh.wikipedia.org/zh-tw/Wireshark

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WireShark
http//www.wireshark.org/download.html
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????

• ?????????
• ????
• 318-1 ???????????????????????????,????????????????
  ????
• 318-2 ???????????????????????????,?????????
• 339-3 ??????????????,?????????????????
  ????????,?????????????,????????,??????????
  ??????????????????????,??
• 352 ???????????????,????????????,???
  ?????????????????
• ?????? ?????

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?? -???????

• 358 ????????????????????????????????
  ,???????????????,??????????????? ?????????
• 359 ?????????????????????????,??????
  ?????,?????????????????????????
• 360 ??????????????????????????,?????
  ??????,????????????????????????
• 361 ??????????????????????,?????????
• 362 ??????????????,????????????,????
  ???????,???????????????????????? ?
• 363 ????????????????,??????

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??????

• Eavesdropping
• OS??
• Password???
• Spoofing
• Session Hijacking
• ??????virus?trapdoor
• DOS, DDOS

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???????
pw????
pw????
??
??
_at_
_at_
Sniffer, WireShark
_at_
eavesdropper
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? ? ? ? ?
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??,???????

• ????(Symmetric Key)??
• KeKd
• ?????(Asymmetric Key)??
• Ke?Kd

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? ?
?????,????????, ?????,?????????? ?????,????????
?? ?,???????,????.? ????????,??????? ??,??????,???
??, ????????,???????, ???????,???????? ???,???????
??,?? ??????????.????? ??,????,???????? ?,????????
?,????. ?????,????????,? ???,????.??,???? ??????,?
????????. ...??????...
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???

• Substitution
• Transposition

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Substitution Ciphers(?????)

• ????????????
• ??apple???????bqqmf?
• I love you ??j mpwf zpv
• ????????, ????????
• ???? Key ??

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Transposition Ciphers
??????? ??????? ?,????? ??????? ??????? ??????? ??
????? ?????? ??????? ,???,?? ??????? ?????? ?????
?? ??????? ,??,??? ????? ??????
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??????? ??????? ?,????? ??????? ??????? ???????
??????? ?????? ??????? ,,???,? ??????? ??????? ?
?????? ??????? ,??,?? ?????? ??????
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26???????????
???? ???? ???? ???? ???? ????
A 0.0856 J 0.0013 S 0.0607
B 0.0139 K 0.0042 T 0.1045
C 0.0297 L 0.0339 U 0.0249
D 0.0378 M 0.0249 V 0.0092
E 0.1304 N 0.0707 W 0.0149
F 0.0289 O 0.0797 X 0.0017
G 0.0199 P 0.0199 Y 0.0199
H 0.0528 Q 0.0012 Z 0.0008
I 0.0627 R 0.0677
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?????

• Caesar Cipher
• Momoalphabetic Cipher
• Hill Cipher
• Playfair Cipher
• Vegenere Cipher (Polyalphabetic cipher)
• Permutation Cipher
• One-Time Pad

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DES(Data Encryption Standard)

• Plaintext M(64 bits)
• Ciphertext C(64 bits)
• Key K(56 bits or 64 bits)
• Round Function F(X, Y)
• X(32 bits) and Y(48 bits)
• Rounds 16

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DES(Cont.)

• IP initial permutation IP(M) (L, R)
• FP final permutation IP.FP FP.IP
• (Ln, Rn) (Rn-1, Ln-1 ? F(Rn-1, K))
• F(X, Y) Perm(S_box( Ext(X) ? Y))
• C FP(R, L)

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DES(Fig.)
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DES(One round)
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Triple DES
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AES (Advanced Encryption Standard)

• Joan Daemen, Vincent Rijmen in Belgium
• 128/192/256 bit keys, 128 bit data
• ?? 4 ??? , 10/12/14 round
• AddRoundKey
• SubBytes
• ShiftRows
• MixColumns

http//zh.wikipedia.org/zh-tw/??????
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AES - AddRoundKey
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AES - SubBytes
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AES - ShiftRows
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AES - MixColumns
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RSA????(?????)

• ?????????
• ??????????p, q(????21024)
• 2005?, 663bit RSA ??Lattice sieve ?
• ??? n p q ? ?(n)(p-1)(q-1)
• ?????? ?(n) ????? e?
• (?? gcd (e, ?(n))1)
• ??????????? d such that
• d ??e d 1 mod ?(n)?
• ?(e, n)? Public key,d? Private key?

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RSA (??)

• (Cd mod n)
• ((Me mod n)d mod n)
• Med mod n
• M(k (p-1) (q-1)) 1 mod n
• M1 mod nM
• (??e d 1 (mod ((p-1) (q-1)))?)
• Fermats little Theorem ??(n) mod n 1
• Where (?,n)1

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RSA (??1)

• ????? p101, q53, n101535353
• ??4657
• ?A?????(eA,NA)(7,5353)
• ???????????????dA743,
• Where eA, dA1 mod (10052)
• ????? 4657743 mod 5353 1003
• ????????(eA,NA )??????
• 10037mod 53534657

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RSA ??2,B?A

• ????? p3, q5
• n3515
• F(n) (3-1)(5-1)8
• ?? m13
• ????11?As Public key (eA,NA)(11,15)
• ??????????? Private key dA3,

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11?F(n) ????
11 8
13-2 3-(8-6) 3-86 (11-8)-82(11-8)
3(11-8)-8 3(11)-4(8) ?Public key 11?F(n)
???? ??(11)????3,????key
8 6
3 2
2
1
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RSA ??2,B?A(Cont.)

• eAdA1131 mod F(n)
• B?As Public key??????1311 mod 15 7
• A ????Private key ????????
• 73mod 1513

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RSA (??3, ??)

• Example(???, p3, q5, n15, e11, d3)
• A???(m13)?A? Private key ??
• 133 mod 157
• B?? (13,7)?As Public key ??????
• 711 mod 15 ????13
• ??????????

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RSA??????

• RSA??exponential algorithm
• RSA?????DES??????
• ???RSA????DES?1000?
• ???RSA?????DES?100?
• ?RSA??????
• digital signature
• protocol??key exchange?

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???? One-way Function

• ????????????? f ?One-way Function
• 1. ??????F??x, ??????f(x)y.
• 2. ????????f ??????y, ?????? ???x ??yf(x)
• Example
• y f(x) xnan-1 xn-1a1xa0 mod p

? f ?
X
Y
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Message Authentication Codes (MAC)

• MAC is an authentication tag (also called a
  checksum) derived by appying an authentic-ation
  scheme, together with a secret key, to a message.
• There are four types of MACs
• (1) unconditionally secure
• (2) hash function-based
• (3) stream cipher-based or
• (4) block cipher-based.

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MAC -2

• Hash function H(m1, m2, , mt)m
• ???Hash function MD5, SHA-1, ...
• MAC is key-dependent one-way hash function
• MAC are computed and verified with the same key
• A B ???? key K
• A send H(K, M) to B
• B can reproduce As result

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???????????

• ?????
• DES, IDEA, AES(MARS, RC6, Rijndael, Serpent, and
  Twofish), ...
• ??????
• RSA, ElGamal, Elliptic Curve Cryptography

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??(1/)

• ?????

Session Key
Session Key
I am Yiter
Asdvh
I am Yiter
DES
DES
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??(2/)

• ??????

?????
??? Public key
???Private Key
_at_SDFGSASDF
I am Yiter
I am Yiter
RSA
RSA
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??(3/)

• ?????????????

???Private Key
??? Public key
Session Key
(
Session Key
RSA
RSA
Session Key
Session Key
I am ???
Dthfgbshgzxcv
I am ???
AES
AES
Bdve_at_dgrse
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??(4/)????

• Example(???, p3, q5, n15, e11, d3)
• ?????(m13)?A???Private key ??????? 133 mod 157
• A ???????(m13, c7)????B
• B ??A? Public key (eA,NA)???????
• m711 mod 15 13
• ?mm ?????

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??(5/) ??????
??
??
Hashing
????
??
Hashing
????
????
????
????
Secret Key
Public Key
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??(6/)

• ?????????????

???Private Key
??? Public key
Session Key
(
Session Key
RSA
RSA
Session Key
Session Key
Dthfgbshgzxcv
Rijndael
Rijndael
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SSL Architecture
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SSL Firefox Example
Https//...
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Firefox - Facebook
Http//...
???
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IE- Facebook
Http//...
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IE-Yahoo
Https//...
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????????

• ????
• ????
• ??

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???? -??,??

• ??????
• Pc cillin (Officescan), Norton, Kaspersky, AVG,
  Avast, Avira (???), PC Tools, Comodo, ClamWin,
  BitDefender, F-Secure, Dr. Web
• ??? spybot
• ????? Ad-aware
• ???? WowUSBProtector, Kavo_Killer

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Firewall

• ??
• ??????????????????????????, ????????
• A firewall system is used to control access to
  or from a protected network ( a site ).
• ??? pcanywhere

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Firewall??
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Firewall ???

• ????????
• ????(Packet Filtering)
• Application Gateway (Dual-homed Gateway)
• Proxy Server
• Screened Host Firewall

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????????

• ???????????????(.log)
• ?????
• ??????
• ???????????????
• ????????????

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????(Packet Filtering)
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??????????

• ????(ICP, UDP, ICMP)??????
• ???????????(port 80, 443...)
• ??????IP?????(.edu)

Block or filter protocols?ports?and?addresses?
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???????

• ??
• Most Common ,easy and cheap
• Fully transparency, no impact to user
• ??
• Little or no logging capability
• Complex filtering rules may become unmanageable
• Rules are difficult to test thoroughly

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Application GatewayDual-homed Gateway
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Application Gateway??
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Application Gateway

• ?????????????, ?????????????
• ????????
• ?Firewall?????, ?????????
• ???????????(FTP, Telnet)
• ???(.log)??????????????
• ??IP?????

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Proxy Server
Proxy Server ??Internet ???????, ????????
???extra logging?and?advanced authentication?
Client
Proxy Server
Remote Server
Cache
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Screened Host Firewall
Screened Host Firewall????? (packet filter)
?????? (application gateway) ???
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Screened Host Firewall

• ?????????????
• ???????????????
• ???????????????
• ???????????????????

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Screened Host Firewall

• ??
• More flexibility.
• Router filtering rules are simplified .
• ??
• Less security. (packet can go directly inside)

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Screened Subnet Firewall
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Subnet v.s. Host Screened
Gateway

• Subnet ? Host????Gateway?????,?????????????????,??
  ?????????????
• ??
• More expensive
• complex management
• Less security if permit special?trusted?service.

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What Cant a Firewall Protect Against

• Firewalls cant protect against attacks that
  dont go through the firewall , or rules that
  make a leak.
• Firewalls cant protect against?data driven?
  attacks , like?Virus?.

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Firewall?????

• ?????
• ???????????????
• ??Firewall?????, ??, ?????
• Firewall????????
• ?????????modem??
• ?????????Internet
• ??????????????????
• Firewall???

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Firewall????

• ?????????
• ??????? Trapdoor
• ???????????????????
• ??????
• Bottleneck
• ?????????
• MIS??, ??????????????

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????

• Electronic Commerce A Managers Guide Kalakota
  Whinston
• William Stallings Cryptography and Network
  Security 5th
• ??
• http//www.rsasecurity.com/
• http//khchu.virtualave.net/index.htm
• http//cissnet.edu.tw ??????
• http//www.nii.org.tw/tanet/docs/???????????.pdf

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