Download Lecture on Security

Class on Security
Raghu
Current state of Security
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Cracks appear all the
time
Band Aid solutions
Applications are not
designed properly
OS designs are not
good
Internet is a can of
worms
Hardware is secure
Applications
Operating
System
Hardware
Problems
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Badly designed Libraries
Trojans exploit Buffer Overflow attack – read
exploits on MDAC
Most attacks originate on the Internet
How?
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Social Engineering
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Messenger
Mail
Problems Continued
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Credit Card thefts are quite common
Passwords are stolen
Social Security is stolen
Why?
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Shared secret
Is shared secret really a secret?
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No
Solutions
 None!
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Not really, none in the current set up
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what can be done?
Some sort of overhaul is required
– So what can we do to avoid shared
secret?
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The first step
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Public – Private Key encryption
You encrypt/decrypt using one key, and the
corresponding decryption/encryption
happens through the other key.
If encryption is done using public key,
decryption is done using private key, and vice
versa.
Public – private key contd
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Your public Key is known to everyone.
Only you have the private key.
All authentication based on challenge response
Your private key is never exposed*
* Standard terms and conditions apply
Example of a Secure System
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SSL – Secure Sockets Layer
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Based on Public Private Key
Server’s Public key is stored at the client side
Data exchanged is encrypted with session key
SSL connection establishment
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Client hello
Server hello
Client sends session key, password
Communication is encrypted using session
key
SSL
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Can someone impersonate server?
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As long as the client knows the public key of the
server - NO
SSL continued
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SSL was designed even before the internet
was up.
SSL is well thought through. It is a nice
example of public – private key scheme that
works.
Public – Private key systems should replace
Shared Secret systems
Digital Certificates
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Alice goes and asks Bob for a certificate.
Bob generates* a public – private key
pair and gives it to Alice.
Bob generates a document and places
on it the following
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Alice’s Name/Info
Alice’s public Key
Bob’s Info which can be the Certificate
Signature
* Is this Completely Correct?
ALICE
Pub Key of Alice
Bob’s Info –
[certificate]
Signature
Signature??
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Bob takes Alice’s Public key and finds its Hash
Then he encrypts the above value with his private
key
This is the signature
Bob’s Private Key
Kpriv[B]
Public Key
Kpub [A]
Hashing
Algorithm
H(Kpub[A])
RSA
Encryptor
Priv[B]{H(Kpub[A])}
So what is a signature
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Your Identity
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The certificate proves that you are indeed who you
claim you are.
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So can I get a certificate in the name Ronaldo Luiz
Nazário de Lima
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Yes
Then what is the point?
You are who you claim?
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I claim to be a person, say Ronaldo for
instance.
I produce a certificate saying the holder of
this certificate is Ronaldo
Now If I do have the private key
corresponding to the public key on the
certificate, then I am indeed the person who
owns the certificate.
So where does that leave us
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Suppose Alice wants to talk to the server Bob
How does Bob know if Alice is indeed Alice?
Digital Certificates helps Bob identify Alice
Suppose Bob trusts Trent
Alice has a certificate signed by Trent, which says –
this certificate belongs to Alice
Bob Sees the certificate and agrees that Alice is
indeed Alice.
Can Mallory steal the certificate and pose as Alice to
Bob?
Stolen Certificates?
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We show our digital certificate everywhere
for authentication.
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So can someone who has seen the
certificate not replicate it.
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Sure, Yes.
So what good is a certificate
Challenge Response
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This problem is solved by challenge
response.
Mallory has Alice’s certificate
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Does she become Alice
Bob does a challenge response.
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He sends a random number encrypted in the
public key on the certificate.
If Mallory produces the random number from the
encrypted value, great, impersonation achieved
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Otherwise she is not the holder of the certificate.
So where can certificates be used
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Authentication
If I have a certificate from ASU, I can get
authenticated using my certificate.
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No ASU id required
No password required
If I have a certificate from my bank, I can log on to
the Bank’s website without a password.
Moreover, If I have a certificate from the government,
do I need to show my Social Security Number at
every step?
Recap
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Shared Secrets are pretty much shared non secrets
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Why? A password is entered on every computer that you
have to log on.
My Social Security # is in a number of offices.
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Wherever I worked on campus
Division of Graduate Studies
Human Resources
Financial Aid Services
Great, so how many people know my secret?
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I have lost count
Recap
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We saw two protocols that work
Why do they work
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They are NOT based on shared secrets
If we all shift to using the public private key
system, my private key will never be revealed*
*Blah, Blah Apply
Will tell the reason in a few slides
Fixing Bad designs
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We saw how to fix the problem of
authentication using Public Private Key
systems
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We saw how to get rid of shared secrets
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What about credit cards?
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That is another mess that can be cleaned
Fixing Credit Cards
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Bob – card Provider
Alice – card holder
Bob provides a credit card based on Public –
private key
Alice signs the hash of a bill using the private
key
Bob decrypts the sign using Alice’s public key
Small Terms and Conditions
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Private Key of a digital certificate is stored on a
computer
How secure is a computer
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Not very secure
What can a Virus do?
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Delete files, format system….,
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Steal your Private Key.
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No this is old hat
Your certificate is as good as nothing
It can install a spurious certificate
Viruses
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How many trojans*/ viruses in the open
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Probably thousands
* NOT USC Trojans
How is a computer made secure
Anti – Virus
 Firewall
 Anti Spyware
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 So these software protect the Computer
 Now who protects these software?
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Attacks on Anti viruses
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Anti virus is a process
It can be easily identified
It can be killed
It can be patched on
Examples
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SpamThru Trojan
Beast
Win32.Glieder.AF
So what am I doing
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Trying to create an anti virus process that is
undetectable
A funky name coined for this project is
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“The Undetectable Virus Detector”
Steganography principles