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Cryptography and Security System 9
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IndexLecture1.1
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Module 1 ( Introduction to Cryptography )Lecture1.2
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Module 2 ( Basics of Cryptography )Lecture1.3
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Module 3 ( Secret Key Cryptography )Lecture1.4
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Module 4 ( Public Key Cryptography )Lecture1.5
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Module 5 ( Cryptographic Hash Function )Lecture1.6
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Module 6 ( Authentication Application )Lecture1.7
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Module 7 ( Security and Firewalls)Lecture1.8
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Module 8 ( IP Security )Lecture1.9
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System Security
(ab tak hamne cryptography ka basics dekha ab aa jate hai System
security pe the next half of subject ab system security naam se hi
pata chalta hai System yani any device which contain information
and system security means uski security ab jaise apko bhi pata hai
hackers and attackers sab bhare hua hai duniya me ab hum cahte
hai apna data aur apne system unse bacha rahe isliye system
security padhna jaroori hai )
Security Attacks
Definition 1 : Anything that compromise the Security of
information owned by any organization is called security attacks
Definition 2 : An attempt to gain unauthorized access to
information resource or services, or to cause harm or damage to
information systems.
( koi bhi voh cheez ya attack jisse organization ki security tutt ti
hai voh security attack hai ab security attack matlab yeh nahi ki
jaake watchman ko maarna security attack means unke computers
ki jo security hai unko chupke se todke unki private information
hasil karna )
There are two types of Security attacks
● Passive Attacks
● Active Attacks
Passive Attacks
❏Passive Attack are a kind of read only attack where attacker is
usually interested in just or make use of information but not affect
or edit system resources
❏The goal of the attacker is to obtain information that has been
transmitted.
❏It is very difficult to detect passive attacks because there is no
alteration.
❏Neither the sender nor the receiver is aware that somebody has
read their message.
❏But we can prevent it by encryption.
(Isme attacker sirf message padta hai par edit or change bilkul
nahi karta hai )
There are Two types of Passive attacks
1. Release of message Content
2. Traffic analysis
Release of message Content
➔It is usually involve monitoring and Analysis of data
transmission to gain some meaningful information out of it .
➔ A telephonic conversation, an E-mail message or a transferred file may
contain confidential data .
➔ This type of attack lay hands directly on this type of communication and
try to access sensitive data.
(isme hackers communication medium like email , telephone call , etc pe
monitoring karte hai aur waha se transferred hua message directly padh lete
hai.)
Traffic Analysis
( yeha pe na attacker direct padh nahi pata par yeh analyse karta hai patterns
ko matlab message ki length kya hai kahase aya hai etc )
➔ Traffic analysis is a special type of inference attack technique that
looks at communication patterns between entities in a system
➔ Traffic analysis is the process of intercepting and examining messages in
order to deduce information from patterns in communication, which can be
performed even when the messages are encrypted.
Active Attacks
( yeh jo attack hota hai na isme apki private information padhi bhi jati hai ,
badli bhi jati hai aur dusro ko bheji bhi jati hai yani apke total lag gaye )
● Active attacks involve modification of data stream or creation of false
data stream.
● Active attack is a network exploit in which a hacker attempts to make
changes to data on the target.
There are Four types of Active attacks
1. Masquerade
2. Replay
3. Modification of message
4. Denial of Services
Masquerade
➔ A masquerade takes place when one entity pretends to be different
entity. ➔ A masquerade attack is an attack that uses a fake identity, such as
a network identity, to gain unauthorized access to personal computer
information through legitimate access identification.
(Best example is voh ladke jo facebook pe ladki ki id banake dusre ladko ko
ullu banate hai that is they are pretending to be someone and they are
masquerade attacker )
Replay
➔ A replay attack (also known as playback attack) is a form of network
attack in which a valid data transmission is maliciously or fraudulently
repeated or delayed.
(pichla save kiya hua message jo pehle bheja ja chuka hai firse saamne
vaale ko bhejna which can lead to break up or salary ka chaque se ek paise
nikal liya usko firse use karne ki try karna )
Modification of message
➔ It simply means that some portion or whole message is changes or
re-order to produce unauthorized effect.
( Simple hai kisi aur ke message ko badalna fir bhejna )
Example :
“Allow Bhuvan to read confidential File account ”
In this message modification is done after modification
“Allow Hola to read confidential File account ”
Denial of Services
➔ Attempt to prevent a computer or service from being available
(suppose last moment tuitions ki website hai jo maximum 100 student ko ek
time pe service de sakti hai ab denial of service me voh 100 bots request
hongi jiski vajah se jo actual student padhna cahte hai voh padh nahi
payenge)
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Difference between Passive and Active Attack
Security Goals
( ab tak humne Security ke baare me padha ab padhenge
Security ke goals kya hai )
There are three main Security Goals
1.Confidentiality
2.Integrity
3.Availability
Confidentiality
➔It ensures that computer related assets (useful
information) are accessed only by authorized parties.
(Confidentiality matlab meri private information ko third
person jisko haq nahi hai padne ka padhna nahi cahiye)
➔Confidentiality is sometimes called secrecy or privacy.
➔Example :
● In military hiding of sensitive information is major
concern
● In industry hiding some information from competitor ●
In banking customer accounts needs to be kept secret.
Integrity
➔Information needs to be changed constantly for example ; In a
bank , when customer deposits or withdraw money , the balance
of his or her needs to be changed
➔Integrity means that changes needs to be done only by
authorized entities and through authorized mechanism.
(Integrity ka matlab hota hai meri information change honi cahiye
par sirf mai yaar authorized person jisko maine haq diya hai vahi
usko change kar sakta hai aur koi nahi )
➔Integrity violation is not necessarily the result of malicious act;
an interruption in the system such as power cut may also create
unwanted changed in some information.
Availability
➔Availability means that the assets (useful information) are
accessible to authorized parties at appropriate times.
➔The information created and stored by an organization needs to
be available to authorized entities
(availability matlab jo mera data hai voh mere liye available hona
cahiye jab mera data meko hi available nahi honga fir voh kis
kaam ka) ➔Information is useless if it is not available
➔Information needs to be constantly changed,which means it
must be accessible to authorized entities
➔The unavailability of information is just as harmful for an
organization as lack of confidentiality and integrity
➔For example : In a bank customer could not access their account
for transactions.
Computer Criminals
1.Computer crime is crime involving computer or aided by the use of one.
2.Anyone committing computer crime is computer criminal. Computer
criminals are intelligent and capable enough.
3.Some computer criminals are mean and sinister types. But many more
wear business suits, have university degrees, and appear to be pillars of
their communities. 4.Some are high school or university students. There are
middle-aged business executives.
5.Some are mentally deranged, overtly hostile, or extremely committed to a
cause and they attack computers as a symbol.
6.Others are ordinary people tempted by personal profit, revenge, challenge,
advancement or Job security.
7.Computer criminals have access to enormous amounts of hardware,
software, and data. 8.The purpose of computer security is to prevent these
criminals from doing damage, One approach to prevention or moderation is
to understand who commits these crimes and why.
1.Amateurs
1.Most of the computer crimes committed are by amateur. Amateurs are
ordinary computer professionals or users who, while doing their
jobs,discover they have access to something valuable.
2.When no one objects, the amateur may start using the computer at work
for their own benefits such as to write letters, or do accounting
2. Crackers or Malicious Hackers
1.System crackers, often high school or university students are the one who
uses computing
system illegally for malicious purpose to harm others.
2.They attempt to access computing facilities for which they have not been
authorized. 3.Cracking a system leaves no direct impact on a system that
can be immediately detected and
involves read stored passwords, information on remote machine
4.Others attack for curiosity, personal gain, or self-satisfaction. And still
others enjoy causing chaos, loss, or harm.
3. Career Criminals
● Since more and more business is now done on internet and using
computers , many computer criminals have realized the ways to use it
illegally for their benefit. ● The career computer criminal understands the
target of computer crime. ● Career criminal involves in crime like illegal
money transfer trading , using confidential information of competitor for
own benefits etc.
● Career criminals are usually difficult to track and prosecute.
4. Terrorists
● Usually terrorists use computer in three ways:
● Targets of attack: Denial-of-service attacks and website defacements are
popular for any political organization because they attract attention to the
cause and bring undesired negative attention to the target.
● Propaganda Vehicles : web-sites , web logs , and email lists are effective ,
fast and inexpensive ways to get a message to many people.
● Method to attack: to launch offensive attacks requires use of computer.
The Methodology of Hacking
The general phases involved in hacking are footprinting, Scanning, gaining
access maintaining access and covering tracks
1. Poet Printing/Reconnaissance
● This phase involves the process of gathering information about the
system to be attacked.
● This information can be collected either internally or externally, that is,
by authorized or unauthorized access.
➔ Social Engineering is a technique which the hacker or person on behalf
of
Hacker smooth talks to people to collect sensitive information like login ids,
passwords to
addresses unlisted phone numbers, etc.
➔ Another way is Dumpster Diving ,where the hacker collect information
from the trash or discarded sensitive information.
● Internet is a big resource of collecting information about different
enterprise systems.
Social Engineering and Dumpster Diving are called as passive
reconnaissance techniques since hacker does not directly interact with the
system
2. Scanning: Pre-attack is another term associated with these phase. ● The
hacker Uses Different tools & techniques to detect vulnerabilities in a
computer system.
● These vulnerabilities may be.
● Open ports: detected using Three-way handshake
● Accessible hasts: detected using ICMP echo request & response ● Router
Location detected using TRACEROUTE
● Network Mapping
● Details of operating system & application running on it
3.Gaining Access:
1.In this phase the hackers may or may not always need access to the
computer system to cause damage.
2.Attacks like denial-of-services of the computer system.
3.This can be done by killing process on the computer system with high
degree of vulnerabiltiy 4.An attacker may use techniques like
spoofing,packet folding.
5.The access gaining depends upon the architecture of the target computer
system, the skill levels of the hackers & the initial level of access obtained.
4. Maintaining Access:
1.Once the hacker gains access to the target system, he/she can use the
access to secure the system to work an ethical hacker or damage the system
to work as an attacker. 2.Sometimes attackers use Trojan to gain access to
the computer system in future. 3.Applications like rootkit can be installed
after gaining to the computer system that enables the hacker to become user
of the system.
5.Covering Tracks:
1.Here the Attackers try to keep themselves hidden and undetected on the
target computer systems.
2.There are different Reasons for this like evading(avoiding) criminal
punishment. maintaining access in future, etc.
3.He/she does this by removing contents of log files that contain
information about events in the system in detail
4.Applications like rootkit help the hacker to hide himself
5.An ethical hacker has to be aware of tools and techniques that may be
developed by attackers to ensure protection of the system.
Classification of Hackers
1. Black Hats: the hackers in this class become crackers
By using talent & computer skills for destruction of the
computer systems. They exploit vulnerabilities and after
gaining access to the computer system, they follow wrong
practices leading malpractice to criminal activities.
2. White Hats: This category of hackers Uses the talent &
computer skills for defence. They work as security analyst
and always think of threats to a computer system and the
countermeasures to be used for it
3. Grey Hats: This category of hackers may work as black
hats and white hats at different times
4. Blue Hats: This category of hackers Work with
computer security consulting firms to bug test system prior
to its launch, looking for exploits so they can be closed.
For example a security professionals invited by Microsoft
to find vulnerabilities in windows.
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