Notes 20110207 CIS 6650 Computer Security
From SnOwy - Ed's Wiki Notebook
Contents |
Partner for Coursework is Ben
- RSA
- 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)
- kds(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.
- M is sent to everyone -- M = Key(Message)
- get Two Large Prime Numbers -- p, q
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)