Security - PowerPoint PPT Presentation

Loading...

PPT – Security PowerPoint presentation | free to download - id: 6f58ef-ZTNlZ



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Security

Description:

Assessing an Organization's Capability to Implement ... ... Security – PowerPoint PPT presentation

Number of Views:204
Avg rating:3.0/5.0
Slides: 72
Provided by: JimC123
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Security


1
Security
2
Reported Security Incidents 1995 2003 Source
http//www.cert.org/present/cert-overview-trends/m
odule-1.pdf
3
Imperative Need for Secure CommunicationCost of
downtime
4
Secure Communication
  • Characteristics of a secure communication
  • Confidentiality
  • Authentication
  • Message Integrity and non-repudiation
  • Availability and Access Control

5
Confidentiality
  • The communicator wants the following to be
    confidential
  • The fact that the communication is occurring
  • Timing of communication
  • Frequency of communication
  • Confidentiality often relies on cryptographic
    techniques for encrypting/ decrypting data using
    one or more keys to encrypt/decrypt data

6
Authentication
  • Both sender and receiver should be able to
    confirm identity of other party involved in
    communication
  • Confirm that the other party is indeed who/what
    they claim to be
  • Authentication relies on authentication
    techniques, several of which rely on
    cryptographic techniques

7
Message Integrity and Non-Repudiation
  • Message integrity
  • Content of communication is not altered
    maliciously or by accident
  • Relies on cryptographic techniques
  • Non-repudiation
  • Not denying what was communicated

8
Availability
  • Can communication occur in first place?
  • Hackers preventing infrastructure from being used
    by legitimate users e.g., viruses, DoS attacks
  • Detect breaches and respond to attacks

9
Access Control
  • Entities allowed to gain access to resources only
    if they have the appropriate access rights (e.g.,
    login ID, passwords, biometric devices)
  • Facilitated by firewalls, which provide access
    control based on a per-packet basis, and on a
    per-service basis.
  • Provide a degree of isolation and protection from
    those outside of ones network

10
Cryptography
  • Symmetric Key Cryptography
  • Public Key Cryptography

11
Symmetric Key Cryptography
  • Symmetric Key Cryptography
  • Caesar Cipher
  • Monoalphabetic Cipher
  • Polyalphabetic Cipher
  • Data Encryption Standard (DES)
  • Triple DES (3DES)
  • Advanced Encryption Standard (AES)
  • Trusted Intermediaries for symmetric key
    distribution
  • Key Distribution Center (KDC)
  • Kerberos

12
Basic Terminology
  • Plain Text
  • Original data not disguised
  • Cipher (Encrypted) Text
  • Disguised data looks unintelligible to intruder
  • Data disguised using encryption algorithm
  • Key
  • A string of s or characters used as input to
    encryption algorithm to disguise plain text
  • Symmetric Key Both parties use same key to
    encrypt and decrypt text

13
Symmetric Key Cryptography
  • Caesar Cipher
  • Each letter in plaintext is substituted with
    letter that is K letters later
  • Wrap around is allowed (i.e., z followed by
    letter a)
  • If K 3, a in plaintext becomes d in cipher text
  • b in plaintext becomes e in cipher text
  • Example Decrypt the following using a Caesar
    Cipher of K 3 Assume wrap around is allowed.
  • L JP J JHHN

14
Symmetric Key Cryptography
  • Data Encryption Standard (DES)
  • Published in 1977, and updated in 1993
  • For commercial and non-classified U.S. Govt. use
  • Encodes plaintext using 56-bit key
  • Objective Scramble data and key so that every
    bit of the cipher text depends on every bit of
    the data and every bit of the key
  • Algorithm Complex (beyond the scope of the
    course) Decryption works by reversing the
    algorithms operations.

15
How well does DES work?
  • DES challenge contest
  • Launched in 1997 by RSA Data Security Inc. -- A
    network security company
  • Encrypted strong cryptography makes the world a
    safer place using a 56-bit DES.
  • Winning team took 4 months to decode.
  • Used volunteers throughout the Internet to
    systematically explore key space.
  • Claimed 10K cash prize after testing only a
    quarter of the key space (about 18 quadrillion
    keys)

16
How well does DES work?
  • In 1999, RSA launched another DES challenge.
  • Message was decrypted in little over 22 hours by
    a network of volunteers and a special purpose
    computer called Deep Crack.
  • Claimed 250 K cash prize.

17
Symmetric Key Cryptography
  • Triple DES (3 DES)
  • If 56-bit DES is considered to be insecure, one
    can simply run the algorithm multiple times,
    using a different key each time
  • DES run three times (with a different 56-bit key
    each time DES is run).

18
Symmetric Key Cryptography
  • Advanced Encryption Standard (AES)
  • NIST in Nov 2001 announced successor to DES.
  • AES is also a symmetric key algorithm that
    processes data in 128-bit blocks
  • AES can operate with 128-bit keys, 192-bit keys,
    and 256-bit keys

19
Trusted Intermediaries
  • Disadvantage of Symmetric Key Cryptography
  • 2 communicating parties have to agree upon their
    secret key ahead of time in a secure manner.
  • Since sender and receiver do not meet face to
    face in the networking world , they need a
    trusted intermediary
  • Trusted Intermediaries
  • Key Distribution Center
  • Kerberos

20
Key Distribution Center (KDC)
  • A server that shares a different secret
    symmetric key with each registered user.
  • KDC knows the secret key of each user, and each
    user can communicate securely with KDC using this
    key.

21
Example Using KDC
  • Assume Sender (S) and Recipient (R) use KDC for
    their communication.
  • Assume Ss secret key known to S and KDC is
    KS-KDC
  • Assume Rs secret key known to R and KDC is
    KR-KDC.

22
Example Using KDC
  • Using key, S sends a message to KDC saying that S
    wants to communicate with R. We denote this
    message as MS-KDC(S, R).
  • KDC decrypts MS-KDC(S, R)
  • KDC generates a random number key KSR, which is
    to be used as symmetric key by S and R during
    their communication.

23
Example Using KDC contd
  • KDC sends S the key KSR, and a pair of values X
    and KSR encrypted using Rs key. We denote this
    message sent back to S by KDC as
  • MKDC-S(KSR, MKDC-R(X, KSR)).
  • S decrypts message and extracts symmetric key
    KSR. S extracts and forwards MKDC-R(X, KSR) to R
  • Note that S cannot decrypt MKDC-R(X, KSR)
  • R decrypts MKDC-R(X, KSR) and uses KSR as
    symmetric key to converse with S
  • R and S communicate using symmetric key KSR

24
Kerberos
  • Developed by MIT
  • Very similar to KDC
  • Has additional functions such as
  • Time stamp for validity of nonce KSR.
  • Has information about which users have access
    privileges to which services on which network
    servers.

25
Public Key CryptographyOverview
  • Define concept of Public and Private keys
  • Demonstrate RSA Algorithm
  • Review Authentication Protocols (ap)
  • Exchanging Public Keys
  • Person in the middle-attack

26
Introduction - Public Key Cryptography
  • Use public key cryptography so that two parties
    can communicate using encryption/decryption
    without using a shared secret key.
  • Key maintenance is difficult
  • Public key cryptography
  • A radically different and marvelously elegant
    approach towards encryption/decryption
  • Also used for authentication and digital
    signatures

27
Basic Idea of Public Key Cryptography
  • Each participant has a private key (known only to
    the participant) and a public key.
  • Public key is made available to others
  • Could be posted even on a website which is
    accessible by the rest of the world.
  • Public key of recipient is used by sender to
    encrypt message.
  • Recipient decrypts message using recipients
    private key.

28
Public Key Cryptography
  • Example
  • Sender (S) wishes to send a message to Recipient
    (R)
  • S fetches Rs public key.
  • S uses Rs public key to encrypt message
  • S sends encrypted message to R.
  • R decrypts cipher text with Rs private key.

29
RSA Algorithm
  • Named after its founders, Ron Rivest, Adi Shamir,
    and Leonard Adleman
  • Has become almost synonymous with public key
    cryptography

30
Using the RSA Algorithm
  • Rs public key is denoted as KR and the private
    key is denoted as KR-.
  • These keys are chosen such that
  • KR- (KR (m)) KR (KR- (m)) m
  • S will encrypt a plain text message, m, using
    public key KR and send it to R

31
Using the RSA Algorithm
  • To encrypt the message, S uses Rs public key and
    determines the cipher text, c as
  • c me mod n
  • To decrypt the message, R uses Rs private key
    and determines the plain text, m as
  • m cd mod n

32
Using the RSA AlgorithmCreate Rs Keys
  • Choose two large prime numbers, p and q.
  • The larger the values, the more difficult it is
    to break RSA, and the longer it takes to
    encode/decode.
  • It is recommended that the product of p and q be
    on the order of 1024 bits for corporate use and
    768 bits for use with less valuable
    information.
  • For a discussion on how to find large prime
    numbers, see http//www.utm.edu/research/primes/pr
    ove/).
  • For example, choose p 5 and q 7

33
Using the RSA AlgorithmCreate Rs Keys
  • Compute n pq 35
  • Compute z (p-1)(q-1) (4)(6) 24
  • Choose a number, e, less than n, which has no
    common factors (other than 1) with z.
  • R chooses e 5
  • Find a number, d, such that ed-1 is exactly
    divisible (that is, with no remainder) by z.
  • d 29
  • Note (ed-1) (5x29 -1) (145-1) 144
  • 144 is exactly divisible by z 24

34
Using the RSA AlgorithmCreate Rs Keys
  • Recap p 5, q 7, n 35, z 24, e 5, d
    29
  • Rs public key is given by
  • KR (n, e) (35, 5)
  • Rs private key is given by
  • KR- (n, d) (35, 29)
  • Example
  • Interpret each letter in the English alphabet as
    a number between 1 and 26. That is, a 1, b
    2, , z 26.
  • S will send message love to R

35
Using the RSA AlgorithmEncrypt Message using KR
(n, e) (35, 5)
Plaintext letter m (numeric representation) m e c me mod n
l 12 248832 17
o 15 759375 15
v 22 5153632 22
e 5 3125 10
  • S will send 17152210 to R

36
Using the RSA AlgorithmEncrypt Message using KR-
(n, d) (35, 29)
Cipher text cd m cd mod n msg
17 481968572106750915091411825223071697 12 l
15 12783403948858939111232757568359375 15 o
22 851643319086537701956194499721106030592 22 v
10 100000000000000000000000000000 5 e

37
RSA and DES/AES
  • RSA is a complex algorithm and uses concepts from
    number theory.
  • DES is at least 100 times faster than RSA.
  • In practice, RSA is often used in combination
    with DES or AES.
  • Message is encrypted using DES key
  • S encrypts DES key with Rs public key
  • R decrypts and obtains DES key with Rs private
    key.
  • Message is decrypted using DES key

38
Authentication
  • ap 4.0 (symmetric)
  • S announces to R, I am S
  • R sends a plaintext nonce ( n) to S.
  • Note nonce is a one time value that is specific
    to that communication session
  • S resends same nonce back to R but this time
    nonce is encrypted with symmetric key used by S
    and R.
  • R decrypts nonce using symmetric key. If
    decrypted nonce equals the nonce sent to S
    earlier (i.e. decrypted nonce n) , then S is
    authenticated.
  • However, this implies that S and R must have
    decided upon and exchanged their symmetric key.

39
Authentication
  • ap 5.0 (public/private)
  • S announces to R, I am S
  • R sends a plaintext nonce ( n) to S
  • S resends same nonce back to R but this time
    nonce is encrypted with Ss private key.
  • R decrypts nonce using Ss public key. If
    decrypted nonce equals the nonce sent to S
    earlier (i.e. decrypted nonce n) , then S is
    authenticated.

40
Exchanging Public Keys
  • Why should public key be publicly available?
  • Wouldnt it be better for S and R to exchange
    their respective public keys via e-mail, after
    authenticating each other?
  • Possibility of person in the middle attack.

41
Person in the Middle Attack
  • S transmits, I am S
  • T eavesdrops.
  • R sends a nonce n.
  • T intercepts nonce, and sends R encrypted nonce
    (encrypted using Ts private key).
  • R sends a message to S asking for Ss public key.
  • T intercepts message, and sends Ts public key to
    R.
  • R decrypts nonce with Ts public key (thinking
    that he is using Ss public key), and
    inadvertently authenticates T.
  • While R is encrypting new data using Ts public
    key, T is busy posing as R to S. In
    particular
  • T transmits Rs nonce to S
  • S transmits encrypted nonce (encrypted using Ss
    private key).
  • T intercepts encrypted nonce, and asks S for her
    public key.
  • S sends her public key

42
Person in the Middle Attack contd
  • R sends encrypted data (encrypted using Ts
    public key)
  • T decrypts using her private key, and finds out
    Rs plain text.
  • T encrypts Rs plain text using Ss public key.
  • T transmits encrypted text to S.
  • S decrypts using her private key, and finds out
    Rs plain text.
  • S and R presume that they have had a secure
    communication. They are ignorant of the fact
    that T has intercepted and decrypted all messages.

43
Availability and Access Control
  • Examples of common attacks
  • Firewalls

44
Examples of some attacks
  • Denial of Service attacks
  • Hacker attempts to disrupt the network by
    flooding the network with messages so that the
    network cannot process messages from legitimate
    users
  • Examples
  • Ping attacks
  • Smurf attack
  • SYN flood attack
  • Distributed Denial of Service attacks

45
Ping Packets
  • Packets that ask a computer to respond with an
    acknowledgement
  • Used to see if a computer is still operational in
    a network
  • Ping by computer name
  • Ping bus.orst.edu
  • Ping by IP address
  • Ping 128.193.76.73

46
(No Transcript)
47
TCP header Packet s (Sequence s)
  • Assume a file has 500,000 bytes
  • Assume TCP breaks this file into packets, where
    each packet size is 1000 bytes
  • Each packet is given a packet
  • The packet for a packet is the number of the
    first byte in that packet.
  • The packet of first packet would be 1
  • The packet of next packet would be 1001
  • The packet of third packet would be 2002 and so
    on

48
TCP Acknowledgement
  • Assume S transmits to R
  • R acknowledges receipt of Ss message, by
    specifying an acknowledgment .
  • The ACK sent by R is the packet of the next
    packet that R is expecting from S.
  • Example
  • After S sends first packet, R sends an
    acknowledgment to S by specifying ACK 1001.
  • After S sends second packet, R acknowledges by
    specifying ACK 2001.

49
SYN Flood Attack
  • Nature of attack
  • Attacker (client) sends a TCP SYN (Synchronize
    Sequence/Packet Number) request to server.
  • The server responds by sending a TCP SYN/ACK
    packet.
  • The attacker does not respond resulting in
    half-open session using up server resources.
  • The attacker sends a flood of such TCP SYN
    requests without responding.
  • Requests from other legitimate clients are unable
    to reach the server due to multiple half-open
    sessions

50
Distributed DoS (DDos) attack
  • In a DDoS attack, a hacker first gains control of
    hundreds/thousands of computers (slaves).
  • Plants software referred to as DDoS agent on each
    of the slaves
  • Hacker then uses software referred to as DDoS
    handler (master) to control the agents (slaves)
  • Attacker launches attacks from all the slaves and
    it is difficult to trace hacker

51
High Profile Victims of DDoS
  • Yahoo, eBay, Amazon, Microsoft and eTrade
    websites have been rendered inaccessible to
    legitimate visitors after being flooded with
    traffic from hundreds of hijacked system
  • www.msn.com www.expedia.com www.carpoint.com
    sites were flooded with DDoS attack for almost
    one day
  • DDoS attack high-level DNS servers on the Internet

52
Firewalls
  • Firewalls are used to prevent intruders on the
    Internet from making unauthorized access and
    denial of service attacks to your network.
  • Examines packets flowing into and out of the
    organizations network (usually via the Internet
    or corporate Intranet), restricting access to
    that network.
  • Two main types of firewalls are packet level
    firewalls and application-level firewalls.

53
Packet-level Firewall
  • Examines the source and destination address of
    packets that pass through it
  • Only allowing packets that have acceptable
    addresses to pass.
  • Since each packet is examined separately, the
    firewall cant understand what the senders goal
    is.
  • Does not monitor the contents of the packets or
    why they are being transmitted and typically does
    not log the packets for later analysis.

54
Packet-level Firewall contd
  • In general, addresses are typically examined at
    the transport layer (TCP Port ID) and network
    layer (IP address)
  • Example 1 Dont allow Telnet (Dest. Port ID 23
    not allowed)
  • Example 2 Dont allow packets from Internet on
    an Intranet (Source IP has to be that of a device
    in the intranet)
  • May be vulnerable to IP spoofing
  • Accomplished by changing the source address on
    incoming packets from their real address to an
    address inside the organizations network.
  • Packet-level firewalls have strengthened their
    security since the first cases of IP spoofing
    (Dec 1994).
  • Example Some firewalls automatically delete any
    packets arriving from the Internet that have
    internal source addresses

55
Application-Level Firewalls
  • Acts as an intermediate host computer, separating
    a private network from the rest of the Internet,
    but it works on specific applications, such as
    Web site access.
  • Application gateway acts as an intermediary
    between the outside client making the request and
    the destination server responding to that
    request, hiding individual computers on the
    network behind the firewall.
  • Because of the increased complexity of what they
    do, application level firewalls require more
    processing power than packet filters which can
    impact network performance.

56
Network Address Translation (NAT)
  • Used to shield a private network from outside
    interference.
  • An NAT proxy server uses an address table,
    translating network addresses inside the
    organization into aliases for use on the
    Internet. So, internal IP addresses remain
    hidden.
  • Many organizations combine NAT proxy servers,
    packet filters and application gateways,
    maintaining their online resources in a DMZ
    network

57
Typical network design using firewalls.
58
Security in many layers
  • 5 layer model
  • Application Layer
  • Transport Layer
  • Network Layer
  • Data Link Layer
  • Physical Layer
  • Each layer can have its own security protocols.

59
Security at Application Layer
  • Secure E-mail
  • PGP (Pretty Good Privacy)
  • e-mail encryption scheme that has become a de
    facto standard.
  • Uses MD5 or SHA for message digest/fingerprints.
  • Uses CAST, 3DES, IDEA for symmetric key
    cryptography
  • Uses RSA for public key cryptography
  • S/MIME (Secure Multipurpose Internet Mail
    Extensions)
  • PEM (Privacy Enhanced Mail)
  • Secure-HTTP or S-HTTP

60
Secure E-mail using PGP
  • When PGP is installed, software creates a private
    key and public key for user.
  • Public key is posted on the website.
  • Private key is protected using a password.
  • Password has to be entered every time user
    accesses private key.

61
Security at Application Layer
  • SET (Secure Electronic Transactions)
  • Developed by MasterCard and VISA in 1997
  • Developed to provide protection from electronic
    payment fraud.
  • SET uses DES for Symmetric Key Cryptography and
    RSA for key exchange.

62
Security at Transport LayerSSL Secure Socket
Layer
  • Developed to provide data encryption and
    authentication between a Web client and a Web
    server.
  • Client and server perform handshake and negotiate
    cryptographic technique to be used.
  • Client and server authenticate each other
  • Encrypted session progresses after handshake is
    completed.
  • SSL is typically applied at the transport layer
  • Implies that SSL is not limited to one
    application
  • Can be applied to Web, e-mail, HTTP applications
    etc.

63
SSL (Continued)
  • SSL was not developed for payment transactions.
  • Assume Bob makes a purchase from ABC Incorporated
    over SSL
  • ABCs certificate issued by CA does not indicate
    whether ABC Incorporated is authorized to accept
    payment card purchases nor if the company is a
    reliable merchant.
  • Similarly, ABC Incorporated has no assurance that
    Bob is authorized to make a payment card purchase
  • May result in stolen credit card transactions,
    customer repudiation of purchased goods.

64
Network Layer SecurityIPSecurity IPSec
  • IPSec is a suite of protocols that provide
    security at the network layer.
  • Complex suite of protocols
  • IPSec would encrypt all parts of the packet
    including user data at application layer, TCP
    header and IP header.
  • Implies that all data sent by hosts e-mail, Web
    pages etc., would be hidden from Intruder.

65
IPSec (Continued)
  • 2 key protocols in the IPSec suite are
  • Authentication Header (AH) protocol
  • provides source authentication and data integrity
    but not confidentiality
  • Encapsulation Security Payload (ESP) protocol
  • provides authentication, data integrity and
    confidentiality.

66
IPSec (Continued)
  • Before sending secure packets, source and
    destination handshake and create a one-way
    (simplex) network-layer logical connection
    known as Security Association (SA).
  • SA is uniquely identified by
  • Security protocol (AH or ESP) identifier
  • Source IP address for simplex connection
  • A 32-bit connection identifier called the
    Security Parameter Index (SPI)

67
SA and Key Management
  • IKE (Internet Key Exchange) algorithm is the
    default key management protocol for IPsec.
  • ISKMP (Internet Security Association and Key
    Management Protocol) defines procedures for
    establishing and tearing down SAs.

68
Security in IEEE 802.11Wireless Network
  • Security Standards are not as advanced in
    wireless environment
  • Since Fall 2004, mobile phones are being attacked
  • Started in Phillipines and has reached U.S.
  • Virus drains your phone battery

69
Wireless Security
  • WEP (Wired Equivalent Privacy) protocol provides
  • Authentication
  • Encryption between a host and a wireless access
    point (WAP)
  • Using symmetric key approach
  • No key management algorithm
  • Authentication carried out using ap4.0

70
Wireless Security
  • However WEP has security holes
  • Updates (as of Feb 22, 2005) on wireless security
    check out
  • http//msnbc.msn.com/id/6998751/
  • http//www.nature.com/news/2005/050221/full/050221
    -6.html
  • http//www.iss.net/wireless/
  • http//www.practicallynetworked.com/tools/wireless
    _articles_security.htm
  • http//www.research.ibm.com/gsal/wsa/

71
(No Transcript)
About PowerShow.com