Class on Security

Raghu

Current state of Security

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

Badly designed Libraries Trojans exploit Buffer Overflow attack – read

exploits on MDAC Most attacks originate on the Internet How?

– Social Engineering Messenger Mail

Problems Continued

Credit Card thefts are quite common Passwords are stolen Social Security is stolen Why?

– Shared secret– Is shared secret really a secret?

No

Solutions

None!– Not really, none in the current set up

So what can be done?– Some sort of overhaul is required– So what can we do to avoid shared

secret?

The first step

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

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

SSL – Secure Sockets Layer– 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

Client hello Server hello Client sends session key, password Communication is encrypted using session

key

SSL

Can someone impersonate server?

– As long as the client knows the public key of the server - NO

SSL continued

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

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– Alice’s Name/Info– Alice’s public Key– Bob’s Info which can be the Certificate– Signature

ALICE

Pub Key of Alice

Bob’s Info – [certificate]

Signature

* Is this Completely Correct?

Signature??

Bob takes Alice’s Public key and finds its Hash Then he encrypts the above value with his private

key This is the signature

Public Key

Kpub [A]

Hashing Algorithm

H(Kpub[A])RSA

Encryptor

Bob’s Private Key

Kpriv[B]

Priv[B]{H(Kpub[A])}

So what is a signature

Your Identity

The certificate proves that you are indeed who you claim you are.

So can I get a certificate in the name Ronaldo Luiz Nazário de Lima

– Yes – Then what is the point?

You are who you claim?

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

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?

We show our digital certificate everywhere for authentication.

So can someone who has seen the certificate not replicate it.– Sure, Yes.– So what good is a certificate

Challenge Response

This problem is solved by challenge response.

Mallory has Alice’s certificate– Does she become Alice

Bob does a challenge response.– 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 achievedOtherwise she is not the holder of the certificate.

So where can certificates be used

Authentication If I have a certificate from ASU, I can get

authenticated using my certificate. – 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

Shared Secrets are pretty much shared non secrets– Why? A password is entered on every computer that you

have to log on.– My Social Security # is in a number of offices.

Wherever I worked on campus Division of Graduate Studies Human Resources Financial Aid Services

– Great, so how many people know my secret? I have lost count

Recap

We saw two protocols that work Why do they work

– 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

We saw how to fix the problem of authentication using Public Private Key systems

We saw how to get rid of shared secrets

What about credit cards?– That is another mess that can be cleaned

Fixing Credit Cards

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

Private Key of a digital certificate is stored on a computer

How secure is a computer– Not very secure

What can a Virus do?– Delete files, format system….,

No this is old hat– Steal your Private Key.

Your certificate is as good as nothing– It can install a spurious certificate

Viruses

How many trojans*/ viruses in the open– Probably thousands

* NOT USC Trojans

How is a computer made secure

Anti – Virus Firewall Anti Spyware

….

….

…. So these software protect the Computer Now who protects these software?

Attacks on Anti viruses

Anti virus is a process It can be easily identified It can be killed It can be patched on Examples

– SpamThru Trojan– Beast– Win32.Glieder.AF

So what am I doing

Trying to create an anti virus process that is undetectable

A funky name coined for this project is– “The Undetectable Virus Detector”

Steganography principles