EMBEDDED SECURITY

EEN 417Fall 2013

9/6/13, Dr. Eric Rozier, V1.0, ECEThanks to Edward Lee and Sanjit Seshia of UC Berkeley

SECURITY

What is Security?

• Compare with:–Reliability = the fraction of time that a system performs its specified function for a specified period of time under stated operating conditions )

What’s different:New kinds of functionsWorst-case adversarial conditions

What is Security?•Secrecy/Privacy• Can secret data be leaked to an attacker?

•Integrity• Can the system be modified by the attacker?

•Availability• Is the system always able to perform its function? • (Is “denial-of-service” possible?)

About this Lecture• Security is increasingly a major concern for embedded systems designers• Voiced by representatives from GM, Boeing, and United Technologies in recent workshop in St. Louis

• Need to know about the security pitfalls in design & implementation of embedded systems

• Security is a full topic, we can’t do it justice in this course.

• EEN 595 – Computer Security – Dr. Zonouz

Authentication

• For a user/process– Establish and verify identity– Make access control decisions

• For a data stream– Validate integrity – Has it been modified by an

untrusted actor?

General Process

Get authentication information

Validate

Set access control restrictions

Allow access

Authentication

• Three factors– Something you have

• Key, card

– Something you know• Password

– Something you are• Biometrics

Multi-Factor Authentication

• Factors can be combined

– ATM system: 2-factor• ATM card• PIN

Password Authentication Protocol

• Reusable passwords• Database stores mappings

– Username:password• Prompt client for key value pair

– Look up in the database and see if they match

Challenge-Handshake Authentication Protocol

• Shared secret• Hash of challenge and secret proves

knowledge of the shared secret.

Server Client

Challenge

Hash(Challenge, Secret)

OK

Problems with PAP

• What if the password file has insufficient protections?

• Even if trusted sources see your password, it may be the key to several systems!

– Hash passwords– Use salt on hashes to prevent dictionary attacks

Another Solution

• One-time passwords– What if the user had a different password each

time?– Generate a list of passwords!

Another Solution

• One-time passwords– What if the user had a different password each

time?– Generate a list of passwords!

• Produces a limited number of authenticated sessions• Relies on one-way functions

One time passwords

• Alice wants to get into Wonderland• Wonderland isn’t happy with reusable

passwords.• Pick a random number, R and a one-way

function f(x)– x1 = f(R)– x2 = f(x1) = f(f(R))– …– x100 = f(x99) = f(f(x98)) = …

One time passwords

• Store x101 in a database for Alice• Alice presents the last number on her list,

x100.• Host computes and compares to x101.

• Next time Alice gives x99.

• Why do it this way?

RSA SecureID

RSA SecureID

• Ask for password (something you know)• Ask for RSA SecureID value (something you

have)

RSA SecureID

• Token computes key– Time of day– Known seed

• (shared secret!)

• Server knows token given a user– Computers key from

seed and time of day

RSA SecureID

• f(seed, PIN, time)

• Intruders lack: seed, f(), PIN

• Stealing card, or PINisn’t enough

More in Laboratory 1!