Notes 20110207 CIS 6650 Computer Security

From SnOwy - Ed's Wiki Notebook

Contents 1 Partner for Coursework is Ben 2 Presentations and Project 3 Steganography 3.1 Watermarks 3.2 Techniques

Partner for Coursework is Ben

• RSA
  1. get Two Large Prime Numbers -- p, q
     • get n = (p-1)(q-1)
     • e ∋ GCD(e, n) = 1
     • d = e^-1(mod n)
     • give to everyone P = (e, n)
     • keep S = (d, n)
  2. k^d_s(mod n) = S(Key) is sent to everyone -- use your partner's public key, not your secret key.
     • where "Key" is a one-time pad.
  3. M is sent to everyone -- M = Key(Message)

Presentations and Project

Steganography

• stego -- hidden writing
• steganos -- (Greek), Steganos = Covered + Graphie = Writing
• unaware of the existence of a message, let alone to decrypt it
• steganalysis -- look for information
  • compare to original (information replaced)
  • noticeable downgrading
  • frequency analysis
• detect (irregularities: date, size, type)
• decode (password / message / software)
• destroy (intercept image, change it in some way, save in different format, or mix of these)

Watermarks

• invisibility
• robustness
• capacity
• must trade off between these three properties

Techniques

• spatial domain
  • least significant bit (LSB)
• transform domain
  • discrete cosine transform (DCT)
  • discrete wavelet transform (DWT)