Module 6 Wireless Network security

WIRELESS NETWORK
SECURITY
MODULE 6

COURSE OUTCOME
Students shall be able to justify security measures, standards,
services and layer wise security considerations in wireless
networks.

OUTLINE
The need, attacks, security serviced, WEP, Mobile IP, VPN( PPTP, LLTP,
IPSec), Network Layer Security, Transport Layer Security,
Email Security: PGP, S/ MIME, Internet Firewalls for Trusted System
Book
Wireless Mobile Internet Security, 2nd Edition, Man, Young Rhee,
Wiley- IEEE press

WIRED EQUIVALENT
PRIVACY (WEP)
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6

WIRELESS NETWORKS SECURITY
More problematic than wired networks
Open transmission media
Susceptible for sniffing
Wide area of coverage
Higher bit error rate
Needs isolation from sensitive data
Requires encryption in transient

WHAT IS ENCRYPTION?
The process of encoding a message or
information
Only authorized parties can access
information
Cryptography is the science
Decryption is the reverse
Encryption= Data Cipher
Decryption= Cipher Data
Sometimes requires a KEY

WIRED EQUIVALENT PRIVACY WEP
Built to suit the IEEE 802.11 Wi-Fi
Targets preserving data confidentiality
Recognizable by its key of 10 or 26
hexadecimal digits
(40 or 104 bits)
Included a method for encrypting data using:
a shared secret
and the RC4 encryption algorithm
Was at one time widely in use

TAXONOMY OF 802.11
AUTHENTICATION TECHNIQUES

SHARED-KEY AUTHENTICATION
MESSAGE FLOW

SHARED-KEY AUTHENTICATION
MESSAGE FLOW
Shared key authentication is a cryptographic technique for
authentication.
It is a simple “challenge response” scheme based on whether a client
has knowledge of a shared secret.
In this scheme, a random challenge is generated by the access point
and sent to the wireless client.
The client, using a cryptographic key that is shared with the AP,
encrypts the challenge (or “nonce,” as it is called in security
vernacular) and returns the result to the AP.
The AP decrypts the result computed by the client and allows access
only if the decrypted value is the same as the random challenge
transmitted.

WEP DRAWBACKS
Shared secrets do not remain secretive
Inability to rotate WEP keys
Produced stagnant shared secret
implementations
Accelerated WEP cracking becoming
common
In 2003 the Wi-Fi Alliance announced
that WEP had been superseded
Eliminate WEP from choices

WI-FI PROTECTED ACCESS (WPA)
Announced by the Wi-Fi alliance in 2003
Security standard for wireless internet connections or Wi-Fi
Improved upon and replaced the Wired Equivalent Privacy (WEP)
Provides more sophisticated data encryption than WEP
Offers user authentication
Two versions of WPA
WPA I in 2003
WPA II in 2004

WPA I
The most common WPA configuration is WPA-PSK (Pre-Shared
Key)
The keys used by WPA are 256-bit
Significant increase over the 64-bit and 128-bit keys used in
the WEP system
Message integrity checks
(to determine if an attacker captured or altered packets between access
point and client)
Temporal Key Integrity Protocol (TKIP)
TKIP employs a per-packet key system

WPA I DRAWBACKS
WPA, like its predecessor WEP, has been shown to be vulnerable to
intrusion via
Proof-of-concept
Applied public demonstrations
The process by which WPA is breached is not a direct attack on the
WPA algorithm
Although such attacks have been successfully demonstrated
Attacks on a supplementary system that was rolled out with WPA
Wi-Fi Protected Setup (WPS)
Designed to make it easy to link devices to modern access points.

WPA II
WPA1 has, as of 2006, been officially superseded by WPA2
Significant changes between WPA and WPA1
The mandatory use of Advanced Encryption Standard AES algorithms
The introduction of CCMP (Counter Cipher Mode with Block Chaining Message
Authentication Code Protocol) as a replacement for TKIP
TKIP is still preserved in WPA2 as a fallback system and for interoperability with
WPA
Security implications of the known WPA2 vulnerabilities are
limited
Recommended to be used on wireless networks now
Available by all wireless devices vendors

WIRELESS SECURITY
MISCONCEPTIONS
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6

GENERAL MISCONCEPTIONS
We aren’t using wireless for
sensitive data
I don’t need to worry about
security
We don’t have any wireless
Organizations often discover that they
have
Rogue Access Point
Unauthorized access points deployed with little
or no security
What about Ad-hoc networks?

MISCONCEPTIONS
We cloak(hide) our SSID (Service set Identifier), so people cannot join
our wireless network
By passively listening to the network, an attacker can capture the network name
There are some software like NSSinssider are free and it is used to show the
broadcasted SSID and hidden SSID
MAC-based access control restricts access to authorized users
An attacker can monitor the network to identify valid MAC addresses and spoof
Mac address with another valid Mac address and fools your Mac address control
WEP is safe
WEP is unsafe
DoS attacks require expensive hardware that is not easily accessible
An attacker can launch DoS attacks with
 $10 wireless card
 Readily-available software
 Can jam your traffic and u find that your machine is not reaching access point

WIRELESS ATTACKS AND
MITIGATION
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6

TAXONOMY OF SECURITY ATTACKS
Figure provides a general taxonomy of security attacks to help
organizations and users understand some of the attacks against
WLANs.

SECURITY ATTACKS
Network security attacks are typically divided into passive and active attacks.
These two broad classes are then subdivided into other types of attacks. All
are defined below.
Passive Attack—An attack in which an unauthorized party gains access to
an asset and does not modify its content (i.e., eavesdropping). Passive
attacks can be either eavesdropping or traffic analysis (sometimes called
traffic flow analysis). These two passive attacks are described below.
– Eavesdropping—The attacker monitors transmissions for message content.
An example of this attack is a person listening into the transmissions on a
LAN between two workstations or tuning into transmissions between a
wireless handset and a base station.
– Traffic analysis—The attacker, in a more subtle way, gains intelligence by
monitoring the
transmissions for patterns of communication. A considerable amount of
information is contained

SECURITY ATTACKS
Active Attack—An attack whereby an unauthorized party makes modifications to a
message, data stream, or file. It is possible to detect this type of attack but it may
not be preventable. Active attacks may take the form of one of four types (or
combination thereof): masquerading, replay, message modification, and denial-of-
service (DoS). These attacks are defined below.
– Masquerading—The attacker impersonates an authorized user and thereby gains
certain
unauthorized privileges.
– Replay—The attacker monitors transmissions (passive attack) and retransmits
messages as the
legitimate user.
– Message modification—The attacker alters a legitimate message by deleting,
adding to,
changing, or reordering it.
– Denial-of-service—The attacker prevents or prohibits the normal use or

EAVESDROPPING MITIGATION
Use strong encryption in the lowest layer protocol possible
Design your wireless networks with caution
Minimize coverage area
Audit your network with a packet sniffer
What can an attacker see?
method by which authorized and unauthorized users are able to get
around normal security measures and gain high level user access
(aka root access) on a computer system, network or software
application.
close the backdoors

MASQUERADING AND MITIGATION
An attacker spoofs his identity as a legitimate node or AP
Tricks unsuspecting users to giving up sensitive information
Tricks an AP into authenticating malicious users
Use mutual-authentication wireless protocols like PEAP or TTLS
Use SSL/TLS for passing sensitive information to Web
applications

DOS MITIGATION
Upgrade the firmware of faulty WiFi cards
Understand the impact of a DoS attack against your
environment
Deploy wireless intrusion detection systems IDS
Prepare a response strategy

ROGUE AP AND MITIGATION
Unauthorized APs connected to a private network
Often installed with default settings, and without security
Permits full access to a network for an unauthorized user
Perform rogue AP detection
Use mutual authentication wireless protocols such as PEAP or
TTLS
Deploy wireless intrusion detection systems
Deploy a strong wireless LAN

SECURE WIRELESS
DESIGN
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6

WIRELESS SECURITY
Consider design at all layers of the OSI model
Identify specific areas for coverage
Audit the WLAN for rogues and unauthorized clients
Consider wireless IDS
Migrate to WPA II

INSSIDER
Tool used to locate access points and determine their SSIDs
MAC address: The hardware address of the device's network adapter
SSID: A 32-character ID that acts like a password on a wireless LAN
Name: The name of the access point, if it is available
Channel: The channel that the device is using
Vendor: The vendor of the device
Encryption: Whether WEP is enabled or disabled

INSSIDER
https://www.metageek.com/products/inssider/

INSSIDER
New in Version 5.0: channel utilization break down to show device
(AP and client) airtime utilization; see connected client devices and
info about client such as utilization and signal strength
Gathers information from wireless card and software
Helps choose the best wireless channel available
Wi-Fi network information such as SSID, MAC, vendor, data rate,
signal strength, and security
Graphs signal strength over time
Shows which Wi-Fi network channels overlap

MOBILE IP
Mobile IP is designed to support host mobility on the internet. User is connected to one
or more applications across the internet, the user’s point of attachment changes
dynamically and that all connections are automatically maintained despite the change.
 Server X transmits an IP datagram for mobile nodes A with A’s address in IP header. IP
datagram is routed to A’s home network.
 At home N/w the incoming IP datagram is intercepted by home agent. The home agent
encapsulates the entire datagram inside a new IP datagram. The use of an outer IP
datagram with a different destination IP address is known as “tunneling”. This IP
datagram is routed to foreign agent.
 Foreign agent strips off the outer IP header, encapsulates the original IP datagram in a
N/w level packet data unit(PDU) and delivers the original datagram to A across the
foreign network.
 When A sends the IP datagram to X, it uses X’s IP address. This is a fixed address that is
X is not a mobile node. Each IP datagram is sent by A to a router on the foreign network
to X. This router is also a foreign agent.
 The IP datagram from A to X travels directly across the Internet to X, using X’s IP
address.

MOBILE IP CAPABILITIES
Registration
Discovery
Tunneling

VPN
A VPN is a private connection between two machines or networks over
a shared or public network. VPN technology lets an organization
securely extend its network services over the Internet to remote
users, branch offices, and partner companies. VPN turn the Internet
into a simulated private WAN.
VPN allows users working at home or office to connect in a secure
fashion to a remote corporate server using the routing infrastructure
provided by a public inter-network (such as the Internet)
The Internet connection over the VPN is encrypted and secure. New
authentication and encryption protocols are enforced by the remote
access server. Sensitive data is hidden from the public, but it is
securely accessible to appropriate users through a VPN

VPN CONNECTION
There are following two ways to create a VPN connection:
By dialing an Internet service provider (ISP):
If you dial-in to an ISP, your ISP then makes another call to the private
network's remote access server to establish the PPTP or L2TP tunnel after
authentication, you can access the private network.
By connecting directly to the Internet: If you are already connected to an
Internet, on a local area network, a cable modem, or a digital subscriber line
(DSL), you can make a tunnel through the Internet and connects directly to
the remote access server. After authentication, you can access the corporate
network.
Host x wishes to send data a data packet to Host y. The data packet at Host
A has the IP address of Host y. Host A transmits the data packet. When the
data packet receives Router Rx, the IP Packet is removed. The Router inserts
the payload field and sends it to Router Ry.
On receiving the packet Router Ry removes the IP Packets and sends it to
Host y in an Ethernet frame.

TUNNELING PROTOCOL
Today for secure data transmission the following tunneling protocols are
used as a result of developments in VPN.
PPTP (Point to Point Tunneling):
This is the most commonly and widely used tunneling protocol. It is available
easily in all the windows operating systems.
It can be easily setup and does processing at high speeds.
For including the PPP data packets the PPTP uses a control channel. It is
dependent on the PPP (Point to point protocol) to provide encryption and
authentication, security to the data packets.
The PPTP protocol tunnels a PP session over and IP network.
It is called point-to-point protocol (PPP) and TCP/IP protocol.

TUNNELING PROTOCOL
Layer 2 Tunneling Protocol (L2TP):
L2TP is tunneling protocol. It is an improved version of PPTP protocol.
It supports LAN-LAN and user-to-LAN connectivity.
It provides data integrity and confidentiality. However it does not provide
any encryption or authentication i.e. it lacks in providing security.
Internet Protocol Security (IPSEC):
It is a collection of multiple related protocols like PPTP, L2TP, it is the most
important protocol used in VPNs.
IPSEC is a layer 3 protocol that authenticates every IP packet.
It uses standard cryptographic methods.
It provides good security.

FEATURES OF A TYPICAL VPN
Keep data confidential (encryption): - Data carried on the public network
must be rendered unreadable to unauthorized clients on the network.
Ensure the identities of two parties communicating (authentication): The
solution must verify the user's identity and restrict VPN access to authorized
users only. It must also provide audit and accounting records to show who
accessed what information and when.
Address Management: It must assign a client's address on the private net
and ensure that private addresses are kept private.
Key Management: It must generate and refresh encryption keys for the client
and the server.
Multiprotocol Support: The solution must handle common protocols used in
the public network. These include IP, Internet Packet Exchange (IPX), and so
on.

DISADVANTAGES OF VPN
The performance of a VPN will be more unpredictable and generally
slower than dedicated lines due to public Net traffic Likewise, many
more points of failure can affect a Net-based VPN than in a closed
private system.

VPN DESIGN
AVPN is connectivity deployed on a shared infrastructure with the
same policies, security, and performance as a private network, but
typically with lower total cost of ownership. The infrastructure used
can be the Internet, an IP infrastructure, or any WAN infrastructure,
such as a Frame Relay network or an ATM WAN.
The following sections discuss these topics:
■ VPN applications
■ VPN connectivity options
■ VPN benefits

VPN APPLICATIONS
VPNs can be grouped according to their applications:
■ Access VPN: Access VPNs provide access to a corporate intranet (or
extranet) over a shared infrastructure and have the same policies as a
private network. Remote-access connectivity is through dial-up,
ISDN, DSL, wireless, or cable technologies. Access VPNs enable
businesses to outsource their dial or other broadband remote access
connections without compromising their security policy.
The two access VPN architectures are client-initiated and Network
Access Server (NAS)– initiated connections. With client-initiated VPNs,
users establish an encrypted IP tunnel from their PCs across an SP’s
shared network to their corporate network. With NAS-initiated VPNs,
the tunnel is initiated from the NAS; in this scenario, remote users
dial into the local SP point of presence (POP), and the SP initiates a
secure, encrypted tunnel to the corporate network.

VPN APPLICATIONS
■ Intranet VPN: Intranet VPNs link remote offices by extending the corporate
network across a shared infrastructure. The intranet VPN services are
typically based on extending the basic remote-access VPN to other corporate
offices across the Internet or across the SP’s IP backbone. Note that there are
no performance guarantees with VPNs across the Internet—no one
organization is responsible for the performance of the Internet. The main
benefits of intranet VPNs are reduced WAN infrastructure needs, which result
in lower ongoing leased line, Frame Relay, or other WAN charges, and
operational savings.
■ Extranet VPN: Extranet VPNs extend the connectivity to business partners,
suppliers, and customers across the Internet or an SP’s network. The security
policy becomes very important at this point; for example, the company does
not want a hacker to spoof any orders from a business partner. The main
benefits of an extranet VPN are the ease of securely connecting a business
partner as needed, and the ease of severing the connection with the business
partner (partner today, competitor tomorrow), which becomes as simple as
shutting down the VPN tunnel. Very granular rules can be created for what
traffic is shared with the peer network in the extranet.

VPN CONNECTIVITY OPTIONS
The following sections describe three connectivity options that
provide IP access through VPNs:
■ Overlay VPNs
■ Virtual private dial-up networks (VPDN)
■ Peer-to-peer VPNs

OVERLAY VPNS
With overlay VPNs, the provider’s infrastructure provides virtual
point-to-point links between customer sites. Overlay VPNs are
implemented with a number of technologies, including traditional
Layer 1 and Layer 2 technologies (such as ISDN, SONET/SDH, Frame
Relay, and ATM) overlaid with modern Layer 3 IP-based solutions
(such as Generic Routing Encapsulation [GRE] and IPsec).

OVERLAY VPNS EXTEND THE
ENTERPRISE NETWORK
■ Every individual virtual circuit must be provisioned.
■ Optimum routing between customer sites requires a full mesh of
virtual circuits between sites.
■ Bandwidth must be provisioned on a site-to-site basis.

VPDNS
VPDNs enable an enterprise to configure secure networks that rely on an ISP
for connectivity. With VPDNs, the customers use a provider’s dial-in (or other
type of connectivity) infrastructure for their private connections. A VPDN can
be used with any available access technology. Ubiquity is important, meaning
that VPDNs should work with any technology, including a modem, ISDN, xDSL,
or cable connections.

VPDN FOR REMOTE ACCESS
Access VPN connectivity involves the configuration of VPDN tunnels.
Following are the two types of tunnels:
■ The client PC initiates voluntary tunnels. The client dials into the SP
network, a PPP session is established, and the user logs on to the SP
network. The client then runs the VPN software to establish a tunnel
to the network server.
■ Compulsory tunnels require SP participation and awareness, giving
the client no influence over tunnel selection. The client still dials in
and establishes a PPP session, but the SP (not the client) establishes
the tunnel to the network server.

PEER-TO-PEER VPNS
In a peer-to-peer VPN, the provider actively participates in customer
routing. Traditional peer-to-peer VPNs are implemented with packet
filters on shared provider edge (PE) routers, or with dedicated per-
customer PE routers. In addition to high maintenance costs for the
packet filter approach or equipment costs for the dedicated per-
customer PE-router approach, both methods require the customer to
accept the provider-assigned address space or to use public IP
addresses in the private customer network.

BENEFITS OF VPN
The benefits of using VPNs include the following:
■ Flexibility: VPNs offer flexibility because site-to-site and remote-access
connections can be set up quickly and over existing infrastructure to extend
the network to remote users. Extranet connectivity for business partners is
also a possibility. A variety of security policies can be provisioned in a VPN,
thereby enabling flexible interconnection of different security domains.
■ Scalability: VPNs allow an organization to leverage and extend the classic
WAN to more remote and external users. VPNs offer scalability over large
areas because IP transport is universally available. This arrangement reduces
the number of physical connections and simplifies the underlying structure
of a customer’s WAN.
■ Lower network communication cost: Lower cost is a primary reason for
migrating from traditional connectivity options to a VPN connection.
Reduced dialup and dedicated bandwidth infrastructure and service provider
costs make VPNs attractive. Customers can reuse existing links and take
advantage of the statistical packet multiplexing features.

BENEFITS OF VPN
Low Cost: The main benefit of a VPN is the potential for significant
cost savings compared to traditional leased lines or dial up
networking. Security: VPNS secure the data access by hackers and
unauthorized users by supporting different authentication methods
and encryption methods.
Scalability: VPNS allow more number of users to be added to their
network easily without modifications in the system infrastructure.
Compatibility with broadband technology: VPN provides efficient and
flexible methods of accessing the network like broadband, ISDN, DSL,
wireless technologies. These connections provide a cost effective
method to connect to the remote offices.

IP SECURITY: IPSEC AND MODES
OF IPSEC
IP SECURITY: ( IPSEC )
IPSEC is a protocol to provide security for a packet at a Network layer which
is often referred to as the Internet Protocol or IP layer.
IPSEC helps to create confidential & authenticated packets for the IP layer.
It can enhance the security of those client / server programs such as
electronic mail, that use their own security protocol.
It can enhance the security of those client / server programs such as HTTP,
that use the security services provided at the transport layer.
It can also be used to provide security to those client /server programs that
do not use the security services provided at the transport layer.
It can provide security for node to node communication programs such as
routing protocols.

MODES OF IPSEC
Modes of IPSEC
Transport mode: - (it only protects the information coming from
Transport layer)
In this mode, IPSEC protects only the packet from the transport layer
not the whole IP packet. Here the IPSEC header & trader are added to
the information coming from the transport layer. The IP header is
added later.
This mode is normally used when we need host to host (end to end
protection of data)

MODES OF IPSEC
Tunnel Mode : ( IPSEC in this mode protects the original IP
header )
 In this mode, IPSEC protects the entire IP packet. It takes an IP
packet, including the header , applies IPSEC security methods
to the entire packet & then adds a new IP header.
 The new IP header, has different information than the original
IP header.
 Tunnel mode is normally used between two route, between a
host & a router or between a router & a host.

PROTOCOLS OF IPSEC
Protocols of IPSEC :
IPSEC defines two protocols
 a. the Authentication Header (AH)
 b. Encapsulation Security Payload (ESP)
to provide authentication and for encryption for the packets at the IP
level.

THE AUTHENTICATION HEADER (AH)
1.Authentication Header (AH) (provide source authentication & data
integrity but not privacy)
AH protocol is designed to authenticate the source host & to ensure
the integrity of the payload carried in the IP packet.
This protocol uses a hash function & a symmetric key to create a
message digest; the digest is inserted via the authentication header.
The AH is then placed on the appropriate location , based on the
mode i .e transport or tunnel.
When an IP datagram carries an authentication header, the original
value in the protocol of the IP header is replaced by the value 51.

THE AUTHENTICATION HEADER
(AH)

(AH)
The addition of an authentication header follows following steps :
An AH is added to the payload with authentication data field set to 0.
Padding may be added to make the total length ever for a particular
hashing algorithm.
Hashing is based on the total packet. However only those fields of the
IP header that do not change during transmission are included in the
calculation of the message digest i.e authentication data.
The authentication data are inserted in the authentication header.
The IP header is added after changing the value of the protocol filed
to 51.

(AH)
Description of every field of AH protocol
1.Next header : The 8 bit header field defines the type of payload carried by
the IP datagrams (such as TCP , UDP, ICMP ). The process copies the value of
the protocol field in the IP datagram to this field. The value of the protocol
field in the new IP datagram is now set to 51 to show that the packet carried
an AH.
2.Payload length : It defined the length of the AH in 4 -byte multiples, but it
does not include the first 8 bytes.
3.Security Parameter index : The 32 but SPI field plays the role of a virtual
circuit identifier & is the same for all packets sent during a connection called
Security Association.
4.Sequence Number : A 32 bit sequence number provides ordering
information for a sequence of datagrams. It prevents a playback. Sequence
number is not repeated even if a packet is retransmitted.
5.Authentication data : This field is the result of applying a hash function to
the entire IP datagram except for the fields that are changed during transit.

ENCAPSULATING SECURITY
PROTOCOL (ESP)
Encapsulating Security Protocol (ESP) (privacy achieved here)
 As AH protocol does not provide privacy , IPSEC comes up with
ESP protocol.
 It provides source authentication , integrity & privacy.
 It adds a header & trailer.
 ESP's authentication data are added at the end of the packet
which makes its calculation easier.
 When an IP datagram carries an ESP header & trailer, the value of
the protocol field in the IP header is 50.
 A field inside the ESP trailer ( next header field) holds the
original value of the protocol field ( the type of payload being
carried by the IP datagram such as TCP or UDP )

PROTOCOL (ESP)
•ESP procedure follows the following steps :
•An ESP trailer is added to the payload.
•The payload & the trailer are encrypted.
•The ESP header is added.
•The ESP header, payload & ESP trailer are used to create the authentication data.
•The authentication data are added to the end of the ESP trailer.
•The IP header is added after changing the protoco value of 50.

PROTOCOL (ESP)
Description for the fields of ESP are as follow :
a. Security parameter index : - The 32 bit security parameter index field is
similar to that defined for the AH protocol.
b. Sequence number : - 32 bit sequence number is also similar to AH
protocol. This variable length field (0 to 25 bytes) of 0s.
c. Padding : Serves as padding.
d. Pad length : The 8 bit pad length field defines the number of padding
bytes, the value is between 0 & 255, the max value is rare.
e. Next header : - The 8 bit next header field is similar to that defined in AH
protocol. It serves the same purpose as the protocol field in the IP header
before encapsulation.
f. Authentication data: Finally authentication data field is the result of
applying an Authentication scheme to parts of the datagram. In AH part of IP
header is included in the calculation of the authentication data whereas in
ESP it is not.

INTERNET SECURITY PROTOCOL:
SECURE SOCKET LAYER
SSL ( Secure socket Layer )
This protocol is used for secure communication between the web browser &
web server.
SSL protocol is located between the application layer & transport layer of the
TCP/IP protocol suite i.e the application layer does not forward the data
directly to the transport layer but it forwards to the SSL layer & the SSL layer
performs encryption.
There are three protocols which are used by SSL :
 Handshake Protocol
 Record Protocol
 Alert Protocol
Handshake Protocol
This is the 1st protocol which is used between the client & the server for
communications.

HANDSHAKE PROTOCOL MESSAGE
•Type indicated the type of message exchanged between the client & server
•Length indicates the length of the message
•Content indicates the actual message or the parameters

PHASES OF HANDSHAKE
PROTOCOL
The handshake protocol consists of four phases :
i. Establish security capabilities
ii. Server authentication 7 key exchange
iii. Client authentication & key exchange
iv. Finish

PHASES OF HANDSHAKE
PROTOCOL
Step 1: Establishing security capabilities
This phase is limited by the client by sending a client Hello Message

PHASES OF HANDSHAKE
PROTOCOL
Step 2 : Server authentication & Key exchange
In this phase the server initiated the communication :
There server first sends its own digital certificates to the client
If the server does not send its own digital certificates to the client in
step 1
The server requires for client’s digital certificate, however this
request id optional.
There server Hello done message indicated the client that the server
portion of Hello message is complete After sending all these
messages, the server waits for the client’s response.

PHASES OF HANDSHAKE
PROTOCOL
Step 3 : Client authenticated & key exchange
This phase is initiated by the client,
The client sends its own certificate to the server, if & only if the server has
requested it.
The client generated a symmetric key which both the parties will use during the
session, It is called as master key secret & the client encrypts it with the server’s
public key & then it sends to the server.
 This step is for client authentication for this client continues the master key secret with the random
no which was agreed by the client & server earlier to generate a has & the client signs it with its own
private key.

PHASES OF HANDSHAKE
PROTOCOL
Step 4: Finish
This phase is initiated by the client.
 The client sends a finish message to the server & the server
replies finish message to the client.

TRANSPORT LAYER SECURITY(TLS)
TLS protocol is the IETF standard version of SSL protocol.
Whose goal is to come out with an internet version of SSL
& TLS are very similar with slight difference. Following are
the differences between TLS & SSL
1. Version : the current version of SSL is 3.0 & TLS is 1.0.
2. Cipher suite : SSL supports an algorithm called Fortezza
whereas TLS does not support Fortezza.
3. Generation of Cryptographic secrets : TLS has more
complex process of generation of cryptographic secrets
than SSL. TLS uses pseudorandom function to create
master secret.
4. Alert protocol : TLS supports all of the alerts defined in
SSL except for no certificate, TLS also added some new
ones like decryption failed, export restriction, protocol

TRANSPORT LAYER SECURITY(TLS)
5. Handshake protocol : TLS has made some changes in Handshake
protocol, The details of the certificate verify message & the finished
message have been changed.
•Certificate verify message in SSL . The hash used in the
certificate verify message is the two step hash of the handshake
message plus a pad and the master secret, TLS has simplified the
process by using hashes only over the handshake messages.
•Finished messages: Hash calculation for the finished message has
also been changed, TLS uses the PRF (pseudorandom function) to
calculate two hashed used for finished message.
6. Record protocol : The only change in this protocol is
the use of HMAC, instead of MAC for signing the
message.

HANDSHAKE PROTOCOL
Pseudorandom Function (PRF)
 PRF is the combination of two date expansion functions, one
using MD5 & the other SHA -1
 PRF takes three input, a secret a label and a seed.
 The label & the seed are concatenated & serves as the seed for
each date- expansion function The secret is divided into two
halves ; each half is used as the secret for each data expansion
function. The output of two data expansion function is
exclusive – ored together to create the final expanded secret.
 As the hashes created froMD5 & SHA-1 are of different sized,
extra section of md5 – based function must be created to
make the two outputs the same size.

EMAIL SECURITY: PGP, S/
MIME
MODULE 6

SECURE MAIL: PGP(PRETTY GOOD
PRIVACY)
 It provide email with privacy, integrity &authentication.
 It can be used to create a secure e-mail message or to store a file
securely for future retrieval.
 PGP provides following services :
 Message integrity
 Message compression.
 Confidentiality with one time session key.
 Code conversion.
 Segmentation
 Most email systems allow the message to consist of only ASCII
characters. To translate other characters not in the ASCII set , PGP uses
Radix 64 conversion. Each character to be sent (after encryption) is
converted to Radix 64 code.
 PGP allows segmentation of the message after it has been converted to
Radix 64 to make each transmitted unit the uniform size as allowed by
underlying e-mail protocol.
 PGP uses following algorithms :
 Public Key Algorithms : RSA ( for signing, encryption ) , Elgamel for encryption only,
DSS.
 Symmetric - Key Algorithm : Blowfish, triple DES.

PGP : - (PRETTY GOOD PRIVACY)
PGP Packets:
-A message in PGP consists of one or more packets -PGP has generic
header that applies to every packets

a. Tag : - This field defines a tag as an 8-bit flag, the 1st bit that is
the most significant is always 1, 2nd bit is 1 if we are using the latest
version. The remaining six bits can define up to 64 different packet
types.
b. Length: The length field defines the length of the entire packet in
bytes. The size of this field is variable, it can be 1,2,or 5 bytes. The
receiver can determine the number of bytes of the length field by
looking at the value of the byte immediately following tag field.
 Case 1: if the value of the byte after the tag field is <192, the length
of the field is only byte.
 Case 2: If the value of the byte after tag field is between 192 to 223
(inclusive ) the length field is two bytes.
 Case 3: If the value of the byte after tag field is between 224 & 254
(inclusive) the length field is one byte. This type of length field
defines only the length of part of the body o .e partial body length.
 Case 4: If it is 255, then length field is of 5 bytes.

Types of data packets:
a. Literal : This type of data packet carries or holds the actual data
that is being transmitted or stored. It is most elementary types of
message, it cannot carry any other packet.

b. Compressed Data Packet : This packet carries compressed data
packets.
Here the data field can be single packet or two or more packets.

c. Data Packet Encrypted with Secret Key : - This packet carries data
from one packet or a combination of packets that have been
encrypted using conventional symmetric key algorithm & before this
packet is sent, a packet carrying one time session key is sent.

d. Signature packet : This packet protects the integrity of the data.

WORKING OF PGP
In PGP, the sender of the message needs to include. the identifiers
of the algorithm used in the message, along with the value of the
keys.
PGP starts with a digital signature. which is followed by
compression, then by encryption, then by digital enveloping and
finally. by Base-64 encoding.
PGP allows for four security options when sending an email
message, These Options are :
 Signature only (Steps 1 and 2 )
 Signature and Base 64 encoding (Steps 1,2 and 5 )
 Signature, Encryption ,Enveloping and Base 64 encoding (Steps 1,2
and 5 )

PGP OPERATION
The receiver has to perform these four steps in the reverse direction
to retrieve the original plain text email message.
Step 1: Digital Signature : This is a typical process of digital
signature, which we have studied many times before. In PGP, it
consists of the creation of a message digest of the email message
using the SHA -1 algorithm. The resulting message digest is then
encrypted with the sender's private key. The result is the sender's
digital signature.

PGP OPERATION
Step 2: Compression : This is an additional step in PGP, Here, the input
message as well as the digital signature are compressed together to reduce
the size of the final message that will be transmitted. For this , the famous
ZIP program is used. ZIP is based on the Lempel Ziv algorithm.
The Lempel Ziv algorithm looks for repeated strings or words and stores
them in variables. It then replaces the actual occurrence of the repeated
words to string with a pointer to the corresponding variable . Since a pointer
requires only a few bits of memory as compared to the original string, this
method results in the data being compressed.
For instance , consider the following string :
What is your name ? My name is Atul.
Using the Lempel Ziv algorithm, we would create two variables, say A and B
and replace the words is and name by pointers to A and B respectively. This
is shown in the figure

PGP OPERATION
As we can see, the resulting string What 1 your 2 ? My 2 1 Atul is
smaller compared to the original string, What is your name ? My name
is Atul. Of course , the bigger the original string, the better the
compression gets The same process works for PGP.

PGP OPERATION
Step 3 : Encryption : In this step, the compressed output of step 2 (i .e the
compressed form of the original email and the digital signature together ) are
encrypted with a symmetric key. For this, generally the IDEA algorithm in CFB
mode is used.
Step 4 : Digital Enveloping : In this case, the symmetric key is used for
encryption with the receiver's public key. The output of step 3 and step 4
together form a digital envelope.

PGP OPERATION
Step 5 : Base 64 encoding : The output of step 4 is Base-64 and is
encoded now.

PGP MESSAGES
-In PGP, a message is a combination of sequenced and/or nested
packets. All the combinations of packets cant make a message, but
still some examples are shown below to give some idea.
a. Encrypted Message: It can be a sequence of two packets, a session
key packet & a symmetrically encrypted packet.

PGP MESSAGES
b. Signed Message : It can be the combination of a signature packet &
a literal packet as shown below

PGP MESSAGES
c. Certificate Message: Certificate can take many forms, one simple
example is the combination of user ID packet & a public - key packet
as shown below
Signature is calculated on the concatenation of the key & user ID.

APPLICATION
Extensively used for personal e-mails.

SECURE MAIL: S/MIME
(SECURE/MULTIPURPOSE
INTERNET MAIL EXTENSION)
It is an enhancement of MIME protocol. –S / MIME adds some new content
types to include security service to the MIME. All these new types include the
parameter " application / pkcs7-mime", in which 'pkcs' defines "Public Key
cryptography Specification"
Cryptographic Message Syntax (cms)
S/MIME has defined CMS, the syntax in each case defined the exact encoding
scheme for each content type. following content type describe the type of
message & different sub types that are created from the messages.
a.Data content types: - This is an arbitrary string. The object created is
called Data.
b.Signed- Data content type: - This type provides only integrity of data. It
contains any type & zero or more signature values. The encoded result is
called signed data. figure below shows the process of creating an object of
this type. following are the steps in the process

following are the steps in the process
1.for each signer ,a message digest is created from the content using
a specific header algorithm chosen by that signer.
2.Each message digest is signal with the private key of the signs.
3.The content signature values , certificates are then collected to
create the 'signed data object'.

c.Enveloped -Data content type :
This type is used to provide privacy for the message. It contains any type &
zero or more encrypted keys & certificated. The encoded result is an object
called enveloped data . Below figure shows the process of creating an object
of this type.
1. A pseudorandom session key is created for the symmetric key algorithm
to be used.
2. For each recipient, a copy of the session key is encrypted with the public
key of each recipient.
3. The content is encrypted using the defined Algorithm & created session
key.
4. The encrypted contents, encrypted session keys, algorithm used &
certificate are encoded using radix 64 .

SECURE MAIL: S/MIME
(SECURE/MULTIPURPOSE
INTERNET MAIL EXTENSION)
d.Encrypted data type content type : This type is used to create an
encrypted session of any content type. This is similar to the
enveloped data content type, the encrypted data content type has no
recipient. It can be used to store the encrypted data instead of
transmitting it. The process is very simple , the user employs any key
& any algorithm to encrypt the content. The encrypted content is
stored without including the key or the algorithm.The object created
is called encrypted data.

Authenticated -Data content type: This type is used to provide
authentication of the data. The object is called authenticated Data.
figure below shows the process.
1.using a pseudorandom generator, a MAC key is generated for each
recipient.
2.The MAC key is encrypted with the public key of the recipient.
3. A MAC is created for the content.
4.The content MAC, algorithms & other information are collected
together to for the authenticated Data object.

KEY MANAGEMENT
The key management in S/MIME is a combination of key management
used by X.509 & PGP. S/MIME uses public-key certificates signed by
the certificate authorities defined by X.509. However, the user is
responsible to maintain the web of trust to verify the signature as
defined by PGP.

APPLICATIONS OF S/MIME
It is predicted that S/MIME will become the industry choice to provide
security for commercial email.

WHAT IS FIREWALL?
Firewall is one of the most effective
security tools
Protects internal network users from
external threats
Resides between two or more networks
Controls the traffic between networks
Helps prevent unauthorized access

FIREWALLS BENEFITS
Protect internal/external systems from attack
Filter communications based on content
Perform NAT (Network Address Translation)
Logging to aid in intrusion detection and forensics

SHORTCOMINGS OF FIREWALLS
Attacks at the application layer may sneak through
Some connections may bypass firewalls like:
Dial-up
Virtual Private Network (VPN)
Extranet
Organizations may let down their guard in other security areas
such as:
Passwords
Patches
Encryption

FIREWALL IN WIRELESS
NETWORK
MODULE 6

FIREWALLS
A firewall is a term used for a ``barrier'' between a network of
machines and users that operate under a common security policy and
generally trust each other, and the outside world.
In recent years, firewalls have become enormously popular on the
Internet.
In large part, this is due to the fact that most existing operating
systems have essentially no security, and were designed under the
assumption that machines and users would trust each other.
A firewall is a system designed to prevent unauthorized access to or
from a private network. Firewalls can be implemented in both
hardware and software, or a combination of both.

REASONS TO USE FIREWALLS
There are two basic reasons for using a firewall at
present:
To save money in concentrating your security on a
small number of components, and to simplify the
architecture of a system by restricting access only to
machines that trust each other.
Firewalls are often regarded as some as an irritation
because they are often regarded as an impediment to
accessing resources. This is not a fundamental flaw
of firewalls, but rather is the result of failing to keep
up with demands to improve the firewall.

HOW ARE FIREWALLS USED?
Firewalls are frequently used to prevent unauthorized Internet users
from accessing private networks connected to the Internet, especially
intranets.
All messages entering or leaving the intranet pass through the
firewall, which examines each message and blocks those that do not
meet the specified security criteria.

DEFAULT RULE
Firewall rule controls the decision of the firewall on inspected
traffic
Controls what happens when a packet does not match an
existing rule:
Default deny- more restrictive
Default allow- more permissive

DEFAULT RULE EFFECT
Default deny helps protect against previously unknown:
Attacks
Vulnerabilities
Consider the effect that the default rule will have on your
security posture
Default Allow is more suitable for educational and training
organizations
Default Deny is more suitable for security authorities and banks

EXAMPLE FIREWALL RULES
IF Source IP==163.121.25.10 AND Destination IP==163.121.11.12
AND Source Port==2050 AND Destination Port==80
Then ACCEPT
IF Source IP==163.121.25.10 AND Destination IP==163.121.11.12
AND Source Port==2050 AND Destination Port==80
Then REJECT
These are detected inside the header of the packet

FIREWALL ACTION
Filtering: Egress filtering (filter outgoing traffic); Ingress filtering
(filter incoming traffic)

TYPICAL FIREWALL DESIGNS
Default-deny approach (white-list): Have a list of allowable traffic and
block the rest.
Default-allow approach (black-list): Have a list of non allowable
traffic and allow the rest. – A good design needs to have a hybrid of
these two approaches

TYPES OF FIREWALLS
Following are the types of Firewalls
Firewalls are used to protect both home and corporate networks.
A typical firewall program or hardware device filters all information
coming through the Internet to your network or computer system.
There are several types of firewall techniques that will prevent
potentially harmful information from getting through:

PACKET FILTER
A packet filter firewall is a stateless firewall that looks at only the
packet headers to decide whether or not to drop a packet.
Stateless means it does not keep track of the decisions taken on any
packet. The decision taken on a packet is independent of the decision
taken on the preceding packets.
The code for packet filters will become lengthy as we want to block
traffic belonging to specific networks, IP addresses and transport
layer protocols.

PACKET FILTER
Thus, need efficient filtering algorithms.
The packet filter firewall applies a set of rules to each & every packet
& based on the rule it will decide whether to accept the packet or
reject the packet.
It receives each packet & checks with the rule.
Suppose the rule is to block all the packets coming from a port other
than 80 then the firewall will block all the packets entering the
internal system.

PACKET FILTER
Attacks Detected by Packet Filters
• IP Spoofing Attacks:
Have the packet filter configured not to let in packets having a source
address that corresponds to the internal network. For example, the
attacker has spoofed the source IP address to be the IP address of a
machine belonging to the network being protected by the firewall.
• Source routing attacks: where source specifies the route that a
packet should take to bypass security measures, should discard all
source routed packets
• Tiny fragment attacks: Intruder uses the IP fragmentation option to
create extremely small fragments and force the TCP header
information into fewer separate fragments to circumvent filtering
rules needing full header info; can enforce minimum fragment size to
include full header.

PACKET FILTER
Looks at each packet entering or leaving the network and accepts or rejects
it based on user-defined rules.
Packet filtering is fairly effective and transparent to users, but it is difficult to
configure. In addition, it is susceptible to IP spoofing.
Packet-filtering firewalls validate packets based on protocol, source and/or
destination IP addresses, source and/or destination port numbers, time
range, Differentiate Services Code Point (DSCP), type of service (ToS), and
various other parameters within the IP header.
Advantages
The primary advantage of packet-filtering firewalls is that they are located in
just about every device on the network. Routers, switches, wireless access
points, Virtual Private Network (VPN) concentrators, and so on may all have
the capability of being a packet-filtering firewall.

PROXY FIREWALLS
Maintains complete TCP connection state and sequencing through 2
connections
User to proxy session
Proxy to destination server session
Process table manages to keep the connections straight
The most secure form of firewall
Slower performance

APPLICATION GATEWAY
Applies security mechanisms to specific applications, such as FTP and
Telnet servers.
This is very effective, but can impose performance degradation.
Application-layer firewalls work on the application level of the TCP/IP
stack (i.e., all browser traffic, or all telnet or ftp traffic), and may
intercept all packets traveling to or from an application.
They block other packets (usually dropping them without
acknowledgment to the sender).
It inspects all packets for improper content, firewalls can restrict or
prevent outright the spread of networked computer worms and
trojans. The additional inspection criteria can add extra latency to the
forwarding of packets to their destination.

APPLICATION GATEWAY
Application Gateway firewall is also called as 'Proxy Server'
The internal user first requests the application gateway such as HTTP,
FTP, telnet Etc.
The application gateway will track the IP address of the user &
provide access to the remote host on behalf of the user.

CIRCUIT-LEVEL GATEWAY
Applies security mechanisms when a TCP or UDP connection is
established.
Once the connection has been made, packets can flow between the
hosts without further checking.
Most circuit-gateway firewalls are implemented using SOCKS, a tool
that includes a set of client libraries for proxy interfaces with clients.
SOCKS receives an incoming connection from clients, and if the
connections are allowed, it provides the data necessary for each client
to connect to the application.
Each client then invokes a set of commands to the gateway. The
circuit-gateway firewall imposes all predefined restrictions, such as
the particular commands that can be executed, and establishes a
connection to the destination on the client's behalf.
To users, this process appears transparent

PROXY SERVER
Intercepts all messages entering and leaving the network. The proxy
server effectively hides the true network addresses.
A proxy server (running either on dedicated hardware or as software
on a general-purpose machine) may act as a firewall by responding to
input packets (connection requests, for example) in the manner of an
application, while blocking other packets.
A proxy server is a gateway from one network to another for a
specific network application, in the sense that it functions as a proxy
on behalf of the network user.

STATEFUL INSPECTION FIREWALL
Unlike packet filtering firewall stateful firewall keeps track of state of
a connection which may be initiation data transfer.
A drawback of packet filters is that they are stateless and they have
no memory of previous packets which makes them vulnerable to
spoofing attacks.
Stateful inspection firewall examines a group of packets at the same
time.
Stateful firewall operates at following layers of OSI model.
 Session
 Transport
 Network

Module 6 Wireless Network security

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Module 6 Wireless Network security