Transcript Chapter 37 Network Security

Chapter 37 Network Security
Aspects of Security

data integrity
– data received should be same as data sent

data availability
– data should be accessible when there is a legitimate need.

data confidentiality and privacy
– data should be protected from unauthorized users
– implemented via username/password mechanism,but data
traversing network is still susceptible to eavesdropping
Encryption

Encrypted message = encrypt (Key, Message)
 Message = decrypt(Key, Encrypted message)

= decrypt(Key, encrypt(Key, Message))
Symmetric Key Encryption

Same key used for encrypting and
decrypting message
 Key known only by sender and receiver
 Eg. DES, RC4
Public Key Encryption

Aka Asymmetric encryption
 uses a pair of keys
– a private key known only to a user
– a public key that is published along with name of user.

message encrypted with private key can only be decrypted
with public key and visa versa.
 Used by SSL protocol to send symmetric key
 M = decrypt (public key, encrypt(private key, Message))
– good for guarantee authenticity of sender

M = decrypt (private key, encrypt(public key, Message))
– good for guarantee privacy of message
Authenticity and
Confidentiality of message

two levels of encryption is used to guarantee that a
message is both authentic and private

double encrypted message

= encrypt( public key receiver, encrypt (private key sender, Message))
Message = decrypt (public key sender, decrypt(private key receiver,
double encrypted message))
Digital Certificates

Electronic document used to identify an
individual, a server, or a company
associated with a public key
 Analogous to driver’s license or passport
 Digital certificates are issued by Certificate
Authority
Digital Signature

Used to sign an electronic document
 A one-way hash (media digest) of electronic
document is encrypted using sender’s private key.
 Recipient can verify that document has not been
tampered by using sender’s public key to recover
the media digest and verifying that this value is
the same as the one-way hash value calculated.
Packet Filters

Implement via Internet firewalls or routers
 used to prevent certain packets from passing
through
 operates by examining fields in the header of each
packet
 network manager specifies boolean combination
of various filter parameters such as source and
destination IP address, or specific protocol service
such FTP or HTTP
Virtual Private Networks
Using pubic network to create “private”
network(fig 37.4)
 minimizes network connection costs
 VPN using routers (fig 37.5)
 IPsec
 PPTP

Network Attacks

denial of service
– Deprives network bandwidth or server resource
– eg. ping flooding via running multiple “ping –s
destIPaddress 12000&”
– Exploits vulnerability in operating system or
application software
– Eg. Viruses and worms, buffer overflow
Good Security Practices

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