e gov security_tut_session_2

1PalGov © 2011

أكاديمية الحكومة اإللكترونية الفلسطينية

The Palestinian eGovernment Academy

www.egovacademy.ps

Tutorial 5: Information Security

Session 2

Internet Risks and Attacks

Dr. Mohammad Jubran

University of Birzeit

[email protected]

mailto:[email protected]

2PalGov © 2011

About

This tutorial is part of the PalGov project, funded by the TEMPUS IV program of the

Commission of the European Communities, grant agreement 511159-TEMPUS-1-

2010-1-PS-TEMPUS-JPHES. The project website: www.egovacademy.ps

University of Trento, Italy

University of Namur, Belgium

Vrije Universiteit Brussel, Belgium

TrueTrust, UK

Birzeit University, Palestine

(Coordinator )

Palestine Polytechnic University, Palestine

Palestine Technical University, PalestineUniversité de Savoie, France

Ministry of Local Government, Palestine

Ministry of Telecom and IT, Palestine

Ministry of Interior, Palestine

Project Consortium:

Coordinator:

Dr. Mustafa Jarrar

Birzeit University, P.O.Box 14- Birzeit, Palestine

Telfax:+972 2 2982935 [email protected]

http://www.egovacademy.ps/

3PalGov © 2011

© Copyright Notes

Everyone is encouraged to use this material, or part of it, but should properly

cite the project (logo and website), and the author of that part.

No part of this tutorial may be reproduced or modified in any form or by any

means, without prior written permission from the project, who have the full

copyrights on the material.

Attribution-NonCommercial-ShareAlike

CC-BY-NC-SA

This license lets others remix, tweak, and build upon your work non-

commercially, as long as they credit you and license their new creations

under the identical terms.

4PalGov © 2011


Session 2: Internet Risks and Attacks

Session 2 Outline:

• Session 2 ILO’s.

• Attacks on Internet Stack (IP, DNS,

UDP, DOS, and DDOS).

• Symmetric and Asymmetric

Cryptography.

5PalGov © 2011

After completing this session you will be able to:

• A: Knowledge and Understanding• a1: Define the different risks and threats from being connected

to networks, internet and web applications.

• a2: Defines security standards and policies.

• a3: Understand the basic principles of cryptography

• B: Intellectual Skills• b1: Illustrate the different risks and threats from being

connected.

• b3: Design end-to-end secure and available systems.

• b4: Design integrity and confidentiality services.

Tutorial 2: Session 5 ILOs

6PalGov © 2011



Session 2 Outline:





Cryptography.

7PalGov © 2011

Types of Attacks Experienced By Percent of Respondents -

2010 / 2011 CSI Computer Crime and Security Survey

8PalGov © 2011


2010 / 2011 CSI Computer Crime and Security Survey continue

2005 2006 2007 2008 2009 2010

Malware infection 74% 65% 52% 50% 64% 67%

Bots / zombies within the organization added in 2007 21% 20% 23% 29%

Being fraudulently represented as sender of phishing messages added in 2007 26% 31% 34% 39%

Password sniffing added in 2007 10% 9% 17% 12%

Financial fraud 7% 9% 12% 12% 20% 9%

Denial of service 32% 25% 25% 21% 29% 17%

Extortion or blackmail associated with threat of attack or release of stolen

data option added in 2009 3% 1%

Web site defacement 5% 6% 10% 6% 14% 7%

Other exploit of public-facing Web site option altered in 2009 6% 7%

Exploit of wireless network 16% 14% 17% 14% 8% 7%

Exploit of DNS server added in 2007 6% 8% 7% 2%

Exploit of client Web browser option added in 2009 11% 10%

Exploit of user’s social network profile option added in 2009 7% 5%

Instant messaging abuse added in 2007 25% 21% 8% 5%

Insider abuse of Internet access or e-mail 48% 42% 59% 44% 30% 25%

Unauthorized access or privilege escalation by insider option altered in 2009 15% 13%

System penetration by outsider option altered in 2009 14% 11%

Laptop or mobile hardware theft or loss 48% 47% 50% 42% 42% 34%

Theft of or unauthorized access to PII or PHI due to mobile device theft/loss option added in 2008 8% 6% 5%

Theft of or unauthorized access to intellectual property due to mobile device

theft/loss option added in 2008 4% 6% 5%

Theft of or unauthorized access to PII or PHI due to all other causes option added in 2008 8% 10% 11%

Theft of or unauthorized access to intellectual property due to all other

causes option added in 2008 5% 8% 5%

10PalGov © 2011



Acting before

attack is why you

are being invited

to this tutorial

11PalGov © 2011

Security TerminologyLecture slides by Lawrie Brown

12PalGov © 2011

Vulnerabilities and Attacks in computer security

• Vulnerability: is a weakness which allows an attacker to

reduce system's information assurance as a result of[1]

– system susceptibility or flaw

– attacker access to the flaw

– and attacker capability to exploit the flaw

• Vulnerable in system resource may result in

– System being corrupted (loss of integrity)

– System being leaky (no confidentiality)

– System is down or doesn’t respond (unavailability)

• Attacks exploited vulnerabilities and may be

– Passive (eavesdropping ,release of message information, traffic

analysis)

– Active (masquerade, replay, modification, denial of service)

[1]: The Three Tenents of Cyber Security". U.S. Air Force Software Protection Initiative. http://www.spi.dod.mil/tenets.htm. Retrieved 2009-12-15.

13PalGov © 2011

Countermeasures to Attacks in computer security

• To deal with computer attacks actions should be taken

(countermeasures) to minimize risks provided few constraints

(complexity, effectiveness, cost, people’s convenience, …)

• Countermeasures may be classified as

– Prevention: to prevent and avoid being attacked

– Detections: to detect attacks in order to handle them

– Recover: to recover and restore the situation after being attacked

14PalGov © 2011

Security Taxonomy

Attacker Tool Vulnerability Action Target Unauthorized

physical design probe accountincrease access

commandImplementati

on scan processdiscloser of information

script or program configuration flood data

corruption of information

autonomous agent authenticate component

denial of service

Info exchange bypass computer

Theft of resources

toolkit spoof network

distributed read internetwork

data tap copy

steal

modify

delete

Lecture slides by Lawrie Brown

15PalGov © 2011

• A denial-of-service attack (DoS attack) or distributed denial-

of-service attack (DDoS attack) is an attempt to make a

computer or network resource unavailable to its intended

users[1]

– network bandwidth

– system resources

– application resources

Classic Denial of Service AttacksGraphics from slides by Lawrie Brown

16PalGov © 2011

TCP Connection Handshake

client server

1

2

3

Send SYN

(seq=x)

Receive SYN

(seq=x)

Send SYN-ACK

(seq=y, ack=x+1)

Receive SYN-ACK

(seq=y, ack=x+1)

Send ACK

(ack=y+1)

Receive ACK

(ack=y+1)

17PalGov © 2011

SYN Spoofing Attack

attacker server

1

2

Send SYN with

spoofed source

address

(seq=x) Receive SYN

(seq=x)

Send SYN-ACK

(seq=y, ack=x+1)

spoofed client

Resend SYN-ACK

after timeout

Assume failed

connection request

Won’t send SYN-ACK

because it didn’t start

the connection

Attacker don’t need a high

bandwidth connection to

start the attack.

Client under attack is

flooded with

18PalGov © 2011

Types of Flooding Attacks

• Flooding attack is a form of DoS attack in which the attacker

try to overload the clients resources

• It can be classified according to the network protocol used

– ICMP Flood

• Rely on the broadcast configuration of the network

• uses ICMP packets, e.g echo request

• typically allowed through because some are required

• the attack usually done as follows:

– Determining the IP address to attack

– Determine a network with good bandwidth and resources to amplify the attack

– Hacker will send huge amount of ICMP packets to a broadcast ip address for the

network, with a spoofed source IP address to point to the client under attack.

– Router or gateway deliver the broadcast at layer 2 to all the hosts in the network.

– Hosts reply to the spoofed address causing a lot of traffic..

19PalGov © 2011

Types of Flooding Attacks continue

– UDP Flood

• send a large number of UDP packets to random port to a specific client

• client will check applications listening to that port

• If none, then will send ICMP destination unreachable

• To avoid being flooded with these packets, attacker may use a spoofed

source address.

• Countermeasure: use firewalls to block unwanted trafic

– TCP SYN Flood

• use TCP SYN (connection request) packets

• but for volume attack

• Countermeasure may include: SYN cookies provide protection against

the SYN flood by eliminating the resources allocated on the target host.

• Limiting the number of connection per source address is not a solution

since attacker may use randomly generated spoofed source addresses.

20PalGov © 2011

Some DoS attacksLecture notes of Prof. Ruby Lee

Attack Affected Area Example Description

Network Level

Device

Routers, IP

Switches,

Firewalls

Ascend Kill II,

“Christmas Tree Packets”

Attack attempts to exhaust hardware resources

using multiple duplicate packets or a software

bug.

OS Level Equipment Vendor

OS, End-User

Equipment.

Ping of Death,

ICMP Echo Attacks,

Teardrop

Attack takes advantage of the way operating

systems implement protocols.

Application Level

Attacks

Finger Bomb Finger Bomb,

Windows NT RealServer

G2 6.0

Attack a service or machine by using an

application attack to exhaust resources.

Data Flood

(Amplification,

Oscillation,

Simple Flooding)

Host computer or

network

Smurf Attack (amplifier

attack)

UDP Echo (oscillation

attack)

Attack in which massive quantities of data are

sent to a target with the intention of using up

bandwidth/processing resources.

Protocol Feature

Attacks

Servers, Client PC,

DNS Servers

SYN (connection depletion) Attack in which “bugs” in protocol are utilized

to take down network resources. Methods of

attack include: IP address spoofing, and

corrupting DNS server cache.

21PalGov © 2011

Countermeasures … to DoS attacksLecture notes of Prof. Ruby Lee

Attack Countermeasure

Options

Example Description

Network Level

Device

Software patches,

packet filtering

Ingress and Egress

Filtering

Software upgrades can fix known bugs and

packet filtering can prevent attacking traffic

from entering a network.

OS Level SYN Cookies, drop

backlog connections,

shorten timeout time

SYN Cookies Shortening the backlog time and dropping

backlog connections will free up resources.

SYN cookies proactively prevent attacks.

Application

Level Attacks

Intrusion Detection

System

GuardDog, other

vendors.

Software used to detect illicit activity.

Data Flood

(Amplification,

Oscillation,

Simple Flooding)

Replication and Load

Balancing

Akami/Digital

Island provide

content distribution.

Extend the volume of content under attack

makes it more complicated and harder for

attackers to identify services to attack and

accomplish complete attacks.

Protocol Feature

Attacks

Extend protocols to

support security.

ITEF standard for

itrace, DNSSEC

Trace source/destination packets by a means

other than the IP address (blocks against IP

address spoofing). DNSSEC would provide

authorization and authentication on DNS

information.

22PalGov © 2011

Distributed Denial of Service Attacks

• Let us read it together: “A Distributed Denial of Service (DDoS) attack uses many computers to launch a coordinated DoS attack against one or more targets. Using client/server technology, the perpetrator is able to multiply the effectiveness of the Denial of Service significantly by harnessing the resources of multiple unwitting accomplice computers which serve as attack platforms. Typically a DDoS master program is installed on one computer using a stolen account. The master program, at a designated time, then communicates to any number of "agent" programs, installed on computers anywhere on the internet. The agents, when they receive the command, initiate the attack. Using client/server technology, the master program can initiate hundreds or even thousands of agent programs within seconds”[1]

[1] Stein, Lincoln. The World Wide Web Security FAQ, Version 3.1.2, February 4, 2002.

http://www.s3.org/security/faq/




23PalGov © 2011

DDoS Control HierarchyGraphics from slides by Lawrie Brown

24PalGov © 2011

Reflection Attacks

• Attacker uses a spoofed source address and send many

requests to many servers

• Servers will respond to the client under attack (his IP is

being spoofed by attacker)

• If many servers response with good speed and bandwidth,

client or target will be flooded with packets.

• Countermeasure: block source spoofed packets

25PalGov © 2011

Amplification AttacksGraphics from slides by Lawrie Brown

26PalGov © 2011

DNS Amplification Attacks

• Attacker uses an ip spoofed DNS inquiry to trigger

a response from the DNS server to the target.

• Attacker try to exploit DNS behavior to convert a

small request to a much larger response

– 60 byte request to 512 - 4000 byte response

• attacker sends requests to multiple servers with

high bandwidth connections, which flood target

– need only moderate flow of request packets

– DNS servers will also be loaded

27PalGov © 2011

DDoS Attack Defenses

• three lines of defense against DDoS:– attack prevention and preemption

– attack detection and filtering

– attack source traceback and identification Avoid initial attack

• Use of Firewalls

• Check incoming/outgoing Packets (filtration)

• Use a server farm and load balancer to offset the effects of a

DDoS attack

• countermeasure SYN flood attacks by discarding the first

SYN packet, this will cause delay for legitimate users.

• Change logical addressing (IP) of attacked systems.

28PalGov © 2011

Attack Prevention

• block spoofed source addresses

– on routers as close to source as possible

– still far too rarely implemented

• rate controls in upstream distribution nets

– on specific packets types

– e.g. some ICMP, some UDP, TCP/SYN

• use modified TCP connection handling

– use SYN cookies when table full

– or selective or random drop when table full

• block IP directed broadcasts

• block suspicious services & combinations

• manage application attacks with “puzzles” to distinguish legitimate

human requests

• good general system security practices

• use mirrored and replicated servers when high-performance and

reliability required

29PalGov © 2011



Session 2 Outline:





Cryptography.

30PalGov © 2011

Symmetric and Asymmetric Cryptography

• Cryptography

– The science and art of engineering and designing ciphers;

• Cryptanalysis

– The science and art of analysing and breaking them;

• Cryptology

– Both the above.

Plain text

encryption

Cipher text

decryption

Plain text

31PalGov © 2011

Standardizing Encryption and Decryption

• We want robust reusable components to do

encryption and decryption.

– Standardize the algorithm; allows public review.

– Concentrate the information that makes the

process unique into a key.

Plain text

encryption

Cipher text

decryption

Plain text

encryption Key

decryption Key

32PalGov © 2011

Symmetric and Asymmetric Systems

• Symmetric encryption: both keys used for encryption

(encryption key) and for decryption (decryption key) are the

same.– Keys are shared secretly (key distribution is an issue to look for)

– Both partes trust each other to keep the keys secret from public.

• Asymmetric encryption: the key used for encryption

(encryption key is different than the one used for decryption

(decryption key), they might be used in different formats.– The two keys are owned and managed separately– One of the keys is kept private, but the other one is made available to public

(public key).

33PalGov © 2011

Symmetric Systems Kinds of Cipher

• There are three common families of cipher:– Substitution ciphers

• Replace each symbol independently of the others

– Stream ciphers• Process each symbol in a way that depends on its position in the input

stream

– Block ciphers• Divide input into blocks and apply the same algorithm to each block in

sequence– but may depend on position in the sequence of blocks.

– Might require adding padding bits (e.g. 14 bits all set to zeros at the end of a

block of 50 bits if the encryption algo. requires blocks of 64 bits)

34PalGov © 2011

Digital Encryption Standard (DES) and 3DES

• DES is a Feistel Cipher– Block size 64 bits

– Key size 56 bits

– 16 stages; each has a 48 bit key formed from the user key

– One-way function (will be discussed later) is SP

• Expand to 48 bits (4 bits to 6 bits)

• Mix in stage key with XOR

• Pass through S-boxes that map 6 bits back to 4 and then permute results.

• Key now generally seen as too short

– Best shortcuts need 242 known texts to recover key.

• Using the current technology, DES has been broken

– broken: plain text can be recovered from the encrypted text within a reasonable

amount of time.

• To improve strength, Triple DES provides three keys

– Three stages

• Encrypt with key one

• Decrypt with key two

• Encrypt with key three

– This structure chosen so that if all three keys are set equal, result is single DES

35PalGov © 2011

Advanced Encryption Standard (AES)

• AES returns to the Substitution Permutation (SP) structure– Used 128 bit (16 byte) blocks and 128, 192 or 256 bit keys

• S-box is 8 bit to 8 bit, derived from group theory to have good properties

• Linear transformation is based on laying data out as a 4*4 grid of bytes

and applying matrix operations

• Bytes from a key stream derived from the user key are added in to each

byte of the matrix to complete the stage.

• There are 10, 12 or 14 stages depending on key length.

• It is expect to hold against cryptanalysis for some time

depending on the advancements of technology and

computations power

36PalGov © 2011

Styles of Block Encryption

• Electronic Code Book– Each block is coded independently.

– this is weak, because equal text blocks give equal cipher texts.

– inference can then be used to break the cipher.

• Chain Coding (Cipher Block Chaining)– Block N is XORed with the encrypted version of block (N-1).

– Start with an agreed initial vector (key).

– the text generated is different each time;

– any change makes the rest of the message unreadable.

Mi encrypt Ci

Ci-1

37PalGov © 2011

Cryptographic Strength

• We can measure the strength of a system in terms of the

number of trials needed to break it in a given situation.

– For brute force attacks this is likely to relate to the effective key size –

e.g. a 16 bit key needs 215 trials on average to find the key.

– However, given more information, such as specific plaintext to cipher-

text correspondences, this number can be significantly reduced.

38PalGov © 2011

Cryptography - Forms of Attack

• Brute force

– Try all keys, assumes you can recognize success!

– Current specialised hardware can do 1011 key tests/sec

• Cut and paste

– If diffusion is low, we can substitute parts of known messages at known offsets in e.g. a banking transaction.

• Known plaintext or known ciphertext

– Shortcut the brute force costs by having examples of matching plain and cipher texts. Inject plaintext to see ciphertext, or inject known ciphertext to see decrypted plaintext.

39PalGov © 2011

• In symmetric cryptography the secret key must be shared

and in public key cryptography the private key need to be

delivered to its owner.

• Key Distribution Center (KDC):

– Jubran and Ahmad need shared symmetric key.

– KDC: server shares different secret key with each registered user

(many users) (KJ-KDC, KA-KDC, KX-KDC)

– Jubran, Ahmad know own symmetric keys, KA-KDC KB-KDC , for

communicating with KDC.

Key Distribution

Ahmad

KA-KDC

Jubran

KJ-KDCX

KX-KDC KDC

KJ-KDC

KX-KDC

KA-KDC

KY-KDC

40PalGov © 2011

Key Distribution Center (KDC)

Q: How does KDC allow Bob, Alice to determine shared

symmetric secret key to communicate with each other?

KDC

KJ-KDC

KX-KDC

KA-KDC

KY-KDC

Alice

knows R1

Uses A,J to

generate R11.KA-KDC(A,J)

2.KA-KDC(R1, KB-KDC(A,R1) )Ahmad

KA-KDC

Jubran

KJ-KDC

41PalGov © 2011

How Useful is a KDC?

• KDC trust may be questionable, it may expose our keys to

others

• Centralized processing and single point of failure

• Must always be online to support secure communication

• In practice, the KDC model is mostly used within single

organizations (e.g. Kerberos) but not more widely.

42PalGov © 2011

Public Key Styles

• The keys are different, one of them is kept private and the other one can be made public, text encrypted by either of them can be decrypted by the other– Confidentiality: sender will encrypt the message using my public key

(known by everyone), but only myself can decrypt the message using my private key (kept secret, known only to me).

– Authentication: I use my private key to encrypt a message (only myself can do that using my private key), anyone who use my public key to decrypt the message is sure that it was encrypted using my private key (myself assuming I kept the private key secret)

– non-repudiation: a message decrypted using my public key is defiantly being encrypted using my private key, and so I can’t deny creating it (off course assuming I kept my key secret).

– Motivation question: a message being encrypted using private key of A, what does the following cases imply

• The message is being decrypted using A’s public key.• The message is being decrypted using B’s public key... (but you don’t know the

original message)? To be discussed next.

43PalGov © 2011

Factoring. RSA Algorithm

• Ciphers based on the problem of factorizing large numbers

which have few prime factors.

•E.g. RSA:

– key is of order 1-2000 bits; message is split into blocks of similar size.

•Find a number N that is the product of two large prime numbers, p and q.

Pick a public exponent e. Secret exponent d is now given by

ed mod (p-1)(q-1) = 1

– N,e is the public key. N,d is the private key

•Infinite possibilities for d and M, and computationally expensive to factor N

into p and q, so encrypted message C is secure

NCM d modulo

NMC e modulo

44PalGov © 2011

Use of PKC in Communications

• Public keys are hard to generate and expensive to use.

• So we try to minimize their use.

– use for exchanges in the authorization process;

– use to transfer a fresh session key;

– use symmetric encryption for the session data;

– change session keys often enough.

45PalGov © 2011

Hash Functions and MACs

• We often want to know whether a message or document has

been modified since its creation.

• Can do this by calculating a smaller value represents the

document

– Changing the document changes this value

– The major concern in deciding what algorithm to use is to avoid

collisions

• In general, a small value representing a larger object is

called a hash and generated by a hash function.

• The hash used in this specific application is called a

message authentication code (MAC) or Message Integrity

Code (MIC).

46PalGov © 2011

Properties of a Hash

• What an attacker will typically be doing is taking a signed document and

trying to change it to another one which has the same hash but different

semantics

– This is why collisions are important – the aim is to find a collision with the

original value.

• Need a wide enough hash, or attacker can just try a series of changes

until a collision is found

– Can play with non-significant content, like white space to find a collision, or

use antonyms e.g. small -> big.

– Documents with a lot of hidden redundant information, such as Word

documents, make this easier.

• One technique is to use message blocks as keys to repeatedly encrypt a

partial hash, mixing input with output to make the process non-invertible.

47PalGov © 2011

Signature

• Just encrypting the text to be signed leaves it open to a

chosen message attack– Get target to sign an apparently innocent nonsense message,

constructed from random data encrypted with their public key and

something you want them to sign;

– Can extract original random bits, which have now been encrypted

with both public and private keys, leaving signed forged message.

• Also asymmetric encryption is computationally expensive

• So form a one way hash of message to be signed, and

encrypt that instead.• This is one area where message digest functions or message

authentication codes (MAC) are used.

48PalGov © 2011

Capabilities

• One particular use of signature is to represent authority

within operating systems.

• Authority is represented by a small capability object

containing– An action id

– A process identity

– Some signature information

• A requested action is permitted if a capability

corresponding to it is also presented

• The operating system supports transfer of capabilities,

changing the signature accordingly

• The cryptographic requirements can be quite weak

because lifetimes are typically short (average process

lifetime).

49PalGov © 2011

Public Key Infrastructure

• What is Public Key Infrastructure (PKI)

1) Set of hardware, software, people, policies, and

procedures needed to create, manage, distribute,

use, store, and revoke digital certificates[1]

2) Simply a system in which public keys are binded to

user identities by means of Certification Authority.

[1]: "LPKI - A Lightweight Public Key Infrastructure for the Mobile Environments", Proceedings of the 11th IEEE International

Conference on Communication Systems (IEEE ICCS'08), pp.162-166, Guangzhou, China, Nov. 2008.

http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4737164




50PalGov © 2011

Certification Authorities

Certification authority (CA)

• generates a signed certificate using CA’s private key

which binds a particular entity to its public key.

• An entity responsible to issue, revoke and manage

digital certificates

– Verify the identity and information provided by the entity

asking for certificate

– may generate private and public keys for entities.

– binds the identity and associated info. of an entity with its

public key using the CA’s private key public key

certificate

– Public key certificates are authentic as they can’t be altered

without detection.

51PalGov © 2011

Certification Authorities continue

• Procedure to obtain a CA signed digital certificate:

– Submit a proof of identity and any other information to be

included in the certificate to CA (usually done offline)

– CA uses its private key to bind the provided information by the

entity to its public key

– Again, the asymmetric key pair might be generated by the

CA, or the public key is provided by the entity itself.

– Again, Certificate contains

• Owner’s distinguished name

• Owners public key

• Issuer’s distinguished name

• Issuer’s digital signature

52PalGov © 2011

Certification Authorities continue

• How to validate a public key within a certificate:

– Get the CA signed certificate (from the entity itself or elsewhere)

– The CA public key must be known for you.

– Use the CA public key to verify the signature within the certificate. “notice: entity info and public key are binded by the CA

private key”

– If the signature is valid then accept the public key.

Digital Certificate of Jubran

· Some info.

· Public key; Kj

· Siganture; Sj

CA public key KCA

Use KCA to verify

the binding

between Sj and Kj

If Kj is truly binded

to Sj then use it

53PalGov © 2011

Certification Authority continue

• Important: you must TRUST the CA in order to TRUST

the digital certificate including the public key signed by

it, and so any digitally signed messages validated

using this public key

54PalGov © 2011

Some General Conclusions

• Cryptography is hard, and widespread testing and

comment is needed– Don’t roll your own – reuse well analysed solutions

• Keep algorithm choice modular– If progress demands greater strength, be able to change

algorithms as a configuration matter

• More is not necessarily better– Offering multiple solutions leads to interworking problems,

and negotiation becomes a vulnerability.

– Don’t encrypt already encrypted material – may have side

effects that weaken the whole system.

55PalGov © 2011

Summary

• In this session we discussed the following:

– Overview and awareness topics on attacks on

Internet Stacks

– More focus was toward denial of service and

distributed denial of service.

– Introduction to cryptography and hash functions

e gov security_tut_session_2

Education