29 November 2010. Documentation Reminders Functional Spec What the program does Context, uses...
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Transcript of 29 November 2010. Documentation Reminders Functional Spec What the program does Context, uses...
SECURITY AND PRIVACY(PART 2)
29 November 2010
Documentation Reminders Functional Spec
What the program doesContext, uses cases, interfaces (definition,
not screen shots)Revise to reflect reality
User manualsDocument, help screens, tool tips, …Describe how handled on your website
Documentation Reminders (2)
Installation Guide & Administrator ManualWhatever is needed to get your system up
○ Including where to find your code or executableMake NO assumptions, BUT you can point to
other documents or web sites (e.g., tell them to download and install a prereq
and give them a web site reference)Assume that the machine that you are running
on caught fire …
Documentation Reminders (3)
Design documentOverall architecture
○ Picture○ Be specific
Decomposition○ Including code file structure
Naming conventionsInterfaces by toolDatabase designDecisions
○ If you were taking over the project, what would you ask?Think of possible enhancements and ask yourself if there is
enough information to get started
ENCRYPTION
Security Level of Encrypted Data
Unconditionally SecureUnlimited resources + unlimited timeStill the plaintext CANNOT be recovered
from the ciphertext Computationally Secure
Cost of breaking a ciphertext exceeds the value of the hidden information
The time taken to break the ciphertext exceeds the useful lifetime of the information
Types of Attacks
Ciphertext only adversary has only ciphertext goal is to find plaintext, possibly key
Known plaintext adversary has plaintext and ciphertext goal is to find key
Chosen plaintext adversary can get a specific plaintext
enciphered goal is to find key
Attack Mechanisms
Brute force Statistical analysis
Knowledge of natural languageExamples:
○ All English words have vowels○ There are only 2 1-letter words in English○ High probability that u follows q○ …
PRIVATE KEY
Caesar Cipher Substitute the letter 3 ahead for each
one Example:
Et tu, BruteHw wx, Euxwh
Quite sufficient for its timeHigh illiteracyNew idea
Enigma Machine(Germany, World War II)
Simple Caesar cipher through each rotor
But rotors shifted at different ratesRoller 1 rotated one
position after every encryption
Roller 2 rotated every 26 times…
Private Key Cryptography Sender, receiver share common key
Keys may be the same, or trivial to derive from one another
Sometimes called symmetric cryptography or classical cryptography
Two basic typesTransposition ciphers (rearrange bits)Substitution ciphers
Product ciphersCombinations of the two basic types
DES (Data Encryption Standard) A block cipher:
encrypts blocks of 64 bits using a 64 bit keyoutputs 64 bits of ciphertextA product cipher
○ performs both transposition (permutation) and substitution on the bits
Considered weakSusceptible to brute force attack
http://www.tropsoft.com/strongenc/des.htm
Cracking DES 1998: Electronic Frontier Foundation
cracked DES in 56 hrs using a supercomputer
1999: Distributed.net cracked DES in 22 hrs
With specialized hardware, DES can be cracked in less than an hour.
History of DES IBM develops Lucifer for banking systems (1970’s )
NIST and NSA evaluate and modify Lucifer (1974) Modified Lucifer adopted as federal standard (1976)
Name changed to Data Encryption Standard (DES) Defined in FIPS (46-3) and ANSI standard X9.32
NIST defines Triple DES (3DES) (1999) Single DES use deprecated - only legacy systems.
NIST approves Advanced Encryption Std. (AES) (2001) AES (128-bit block) Attack published in 2009
Current state of the art is AES-256
PUBLIC KEY
Public Key Cryptography
Two keysPrivate key known only to individualPublic key available to anyone
○ Public key, private key inverses
Confidentialityencipher using public keydecipher using private key
Integrity/authenticationencipher using private key decipher using public one
Public Key Requirements
1. Computationally easy to encipher or decipher a message given the appropriate key
2. Computationally infeasible to derive the private key from the public key
3. Computationally infeasible to determine the private key using a chosen plaintext attack
RSA Public key algorithm described in 1977 by
Rivest, Shamir, and Adelman Exponentiation cipher Relies on the difficulty of factoring a large
integer RSA Labs FAQ document (good intro)
http://www.rsasecurity.com/rsalabs/node.asp?id=2152
RSA Usage for Encryption Public key: (n,e); private key:
(n,d)Public key to encipherPrivate key to decipher
EncryptionEncipher: c = me mod nDecipher: m = cd mod n
RSA Basics for choosing keys Choose two large primes p and q n = pq Choose e
Less than nRelatively prime to (p-1)(q-1)
Choose d(ed-1) divisible by (p-1)(q-1)
Public key: (n,e); private key: (n,d)
A Guide to RSA
Summary Private key (classical) cryptosystems
encipher and decipher using the same key Public key cryptosystems
encipher and decipher using different keyscomputationally infeasible to derive one
from the other
AUTHENTICATION
Authentication
Assurance of the identity of the party that you’re talking to
Primary technologiesDigital SignatureKerberos
Digital Signature Authenticates origin, contents of message in a
manner provable to a disinterested third party (“judge”)
Sender cannot deny having sent message (service is “nonrepudiation”)Limited to technical proofs
○ Inability to deny one’s cryptographic key was used to sign
One could claim the cryptographic key was stolen or compromised○ Legal proofs, etc., probably required
Protocols based on both public and private key technologies
RSA for Digital Signature
Public key: (n,e); private key: (n,d)Public key to signPrivate key to validate
Digital signatureSign: s = md mod n; send (s,m)Validate: m = se mod n
Kerberos Authentication system
Central server plays role of trusted third party Ticket (credential)
Issuer vouches for identity of requester of service
Authenticator Identifies sender
User must1. Authenticate to the system2. Obtain ticket to use server S
Problems Relies on synchronized clocks Vulnerable to attack
“Using encryption on the Internet is the equivalent of arranging
an armored car to deliver credit card information from someone
living in a cardboard box to someone living on a park bench”
– Gene Spafford (Purdue)
NETWORK SECURITY
Firewall Techniques Filtering
Doesn’t allow unauthorized messages through Can be used for both sending and receivingMost common method
ProxyThe firewall actually sends and receives the
informationSets up separate sessions and controls what
passes in the secure part of the network
DMZ: Demilitarized Zone
Arrangement of firewalls to form a buffer or transition environment between networks with different trust levels
Internet Firewall
Firewall
Internal resources
Three Tier DMZ
Internet Firewall
Firewall
Firewall
Internal resources
WebServer
AppServer
PRIVACY
When you walk into the store, the big-screen displays "Hello Tom," your shopping habits, and other information
from Minority Report
Some Views on Privacy “All this secrecy is making life harder, more
expensive, dangerous …”Peter Cochran, former head of BT (British Telecom)
Research
“You have zero privacy anyway.”Scott McNealy, CEO Sun Microsystems
“By 2010, privacy will become a meaningless concept in western society”
Gartner report, 2000
Legal Realities of Privacy Self-regulation approach in US, Japan Comprehensive laws in Europe,
Canada, Australia European Union
Limits data collectionRequires comprehensive disclosuresProhibits data export to unsafe countries
○ Or any country for some types of data
Aspects of Privacy
Anonymity Security Transparency and Control: knowing
what is being collected
Privacy and Trust Right of individuals to determine if, when,
how, and to what extent data about themselves will be collected, stored, transmitted, used, and shared with others
Includesright to browse the Internet or use applications
without being tracked unless permission is granted in advanced
right to be left alone True privacy implies invisibility Without invisibility, we require trust
Technologies privacy aware technologies (reactive)
non-privacy-related solutions that enable users to protect their privacy
Examples○ password and file-access security programs○ unsubscribe○ encryption○ access control
privacy enhancing technologies (proactive) solutions that help consumers and companies protect
their privacy, identity, data and actions Examples
○ popup blockers○ anonymizers○ Internet history clearing tools○ anti-spyware software
Impediments to Privacy Surveillance Data collection and sharing Cookies
Web site last year was discovered capturing cookies that it retained for 5 years
Sniffing, Snarfing, SnortingAll are forms of capturing packets as they pass
through the networkDiffer by how much information is captured and
what is done with it
P3P
Platform for Privacy PreferenceWorld Wide Web Consortium (W3C) project
Voluntary standard still in draft form Structures a web site’s policies in a
machine readable formatAllows browsers to understand the policy
and behave according to a user’s defined preferences
Privacy and Wireless “Wardriver” program: scans for broadcast
SSIDsbroadcasting improves network access, but at a cost
once the program finds the SSIDobtains the IP addressobtains the MAC address…
Lowe’s was penetrated this wayStole credit card numbers