SystemsSec 2016W Lecture 10

Topics & Readings

• Updates
• Computer Security Research
• Secure Hashes
• TLS
• SSH

Class Notes

Updates

Literature Review Papers

• Assignments are being replaced with a literature review paper (a paper in which a collection of papers are analyzed and discussed)
• End of March: submit a small literature review paper (possibly written in a group of 3 to 4 people)
• Multiple grading schemes at end of semester (20% literature review paper, 10% hacking journal and vice-versa)

Midterm and Final Exam

• Midterm and final will be essay-based; sample questions will be provided to help with studying
• Midterm topics to be announced in a in a future lecture

Hacking Journals

• During reading week, you will receive a mark for your hacking journals to-date
• After reading week, the course will be mostly focused on research papers
• Going forward, focus of hacking journals should be to go in-depth rather than breadth
• Hacking journals likely to end by mid-March

Computer Security Research

• Unlike other computer science disciplines, computer security revolves around conferences
• Academic conferences and non-academic conferences (e.g., Defcon and Black Hat) have different purposes
• Submitted papers at respectable academic conferences tend to have an acceptance rate of 20% or less
• Big Four Conferences
  • IEEE Symposium on Security and Privacy (S&P); formerly known as the Oakland Conference http://www.ieee-security.org/TC/SP-Index.html
  • ACM Computer and Communications Security (CCS) http://www.sigsac.org/ccs.html
  • USENIX Security Symposium https://www.usenix.org/conference/usenixsecurity15
  • ISOC Network and Distributed Systems Security (NDSS) http://www.internetsociety.org/events/ndss-symposium
• Other well-respected conferences:
  • SOUPS (Symposium On Usable Privacy and Security) https://cups.cs.cmu.edu/soups/
  • ACSAC (Annual Computer Security Applications Conference); caters to application of security in the US military http://www.acsac.org/
  • FC (Financial Crypto) http://fc15.ifca.ai/
  • NSPW http://www.nspw.org
• Browse conference websites to find interesting topics for your literature review paper
• If working individually, paper should be approximately 10 pages double-spaced.

Secure Hashes

• Generating one can be done on command line (md5sum, sha1sum, sha256sum)
• MD5 represents a 128-bit hash as a 32 digit hexadecimal; usage is discouraged since it has been terribly compromised
• SHA-1 hashes are bit longer but have also been compromised; Google is discouraging SHA-1 for websites and SSL encryption by displaying warnings in Chrome
• SHA-256 is recommended
• A property of any secure hash: a 1-bit change in input must lead to, on average, half of the bits changing in the output
• Generally, it is computationally impossible to reverse a hash unless the hash function is broken in which case, shortcuts can be used.
• Computationally infeasible to break SHA-256 right now
• A birthday-attack is a fast brute force attack on a crypto algo (example: decreasing search space to increase chances of collision)
• Common use of hashes: software distribution (e.g., ISOs, disk images, BitTorrent)
  • This allows you to verify that integrity of a download
  • Caveat: if someone can alter your download, they can likely alter the publicly listed hash
• Key terminology
  • RSN: robust secure network
  • AES: block cipher
  • SHA256: Hash function

TLS

• protocol used to talk to web server securely with a secure, encrypted connection
• algorithms: AES is the block cipher used, GCM is the mode, RSA is part of the public key exchange
• Diffie-Hellman: the first public key algorithm that was created; used for key exchange, not authentication;
  • example: talking to someone across the world
  • in order to have a secure channel to talk with them, you can use block ciphers
  • block ciphers require shared keys

SSH

• “known_hosts” file located in your /.ssh folder contain public keys of machines that you can connect to
• “authorized_keys” contains public keys of machines that you have authorized to connect to your machine
• if a public key changes, you’ll get an error
• Large corporations use their own certificates
  • provides a secure connection to their proxy
  • let’s them monitor activity
• Encryption can very easily be your enemy