Notes 20110307 CIS 6650 Computer Security

From SnOwy - Ed's Wiki Notebook

Presentations today ...

Contents 1 Administrivia 2 Cryptosystem 2.1 DES 2.2 Alterntives since DES was broken 3 Watermarking for Medical Applications (Presentation) 4 Eavesdropping, Impersonation and Denial of Service 5 Viruses, Worms, Access Violations, Certificates, PKI1

Administrivia

• Next week: Quiz
  • mostly theory since we covered most of the math last time
  • some math: RSA
• Presentation -- next week
• Project proposal -- Wednesday

Cryptosystem

DES is complicated -- I'll have to sit down and explain it here later ...

DES

• 1972-1974 -- asked for a good cryptosystem
• Horst Feistel's Lucifer Cipher
• 1976 -- Lucifer renamed DES after modification on NSA
• shorter key, longer S-box
• twenty years later: DES became routinely broken
• DES uses block ciphering -- every eighth bit is a checksum
• block cipher design
• DES only performs two operations
  • bit shifting (permutation)
  • bit substitution
• DES works on 64 bits of data at a time
• each bit is iterated from 1 to 16 times (16 is the standard)
  • that means we're actually encoding the data repeatedly
• 56-bit key, 64-bits total; 8-bits are checksums
  • checksums -- integrity
• 16 48-bit subkeys are generated
• 56-bit key from PC-1 (?)
• 48-bit subkey chosen from PC-2 (?)
• message is halved
• first half undergoes expansion permutation
• ... no new bits are introduced -- existing bits are repeated and shuffled around
• S-boxes are matrices of numbers used to perform the bit permutations
• we can think of S-boxes as logical circuits or functions -- they take 48-bits of input and produce 32-bits of output
• ... return later.

Alterntives since DES was broken

• Triple DES -- too slow
• GOST
• AES

Watermarking for Medical Applications (Presentation)

Speaker: Ahmed Mahmood

• telemedicine security
• watermarking improves data integrity
• watermark presents a lot of identifiable information
• in case of breach of security, able to tell who leaked the data
• watermarking chosen -- little information total
  • contrast steganography -- used if there is a known large amount of information to encode
• problem
  • select the area to place the watermark
• contrast with previous techniques
  • envelope watermarking -- draw a thick border around image and place mark therein
    • not robust, can be removed with cropping
  • polygon watermarking method
    • limited, can only be used on things like ultrasounds with regular background space

Eavesdropping, Impersonation and Denial of Service

Speaker: Benjamin Ferriman

• eavesdropping -- everyone seems to be doing this
  • government -- phone, ISPs, criminal, social media
  • commercial -- employee productivity, company resources, ISP throttling
  • personal -- private investigation, hobbyist
• impersonation
  • computer -- forged SSL certificate; spoofed Media Access Control MAC adress; session hijacking
    • firesheep -- steal a session
    • Cain, SSLStrip, SSLSniff -- create a false SSL certificate for a website
  • humans -- social engineering

Viruses, Worms, Access Violations, Certificates, PKI1

Speaker: Nan Wu

• virus -- small piece of software -- attaches to legitimate binaries
• overwrite viruses -- delete information
• direct action viruses -- replicate and take action when executed
• worms -- small piece of software, uses networks and security holes to replicate
• original worm was designed to be helpful in moderating network traffic
• access violation -- process attempts to access memory reserved for operating system