57 posts found

Illustration of "Spamicity"

Spam = unsolicited annoying mails, scam. Difficult to evaluate. Lot of methods to improve click rate (email source, url quality, https, personalised with name, ...)

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Illustration of "System Architecture: Core, Scheduling, Memory"

 Memory architecture

 Processor architecture

The computer has a processor, which contains cores. Each core contains FPU (Floating Point Unit), ALU (Arithmetic and Logic Unit), registers (very quick memory 1-3 cycles to access), caches (L1, L2, L3 for each core or shared in the whole CPU). The computer also has RAM (80 cycles) and mass-storage memory (milliseconds).

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Illustration of "System security 22 1/2"

ENT test

Find false randomness (not a proof to true randomness)

  • entropy
  • compression
  • chi-square
  • arithmetic mean
  • montecarlo estimation for PI
  • serial correlation coefficient)


Example: Entropy = 7.980627 bits per character.

Optimum compression would reduce the size
of this 51768 character file by 0 percent.

Chi square distribution for 51768 samples is 1542.26, and randomly
would exceed this value less than 0.01 percent of the times.

Arithmetic mean value of data bytes is 125.93 (127.5 = random).
Monte Carlo value for Pi is 3.169834647 (error 0.90 percent).
Serial correlation coefficient is 0.004249 (totally uncorrelated = 0.0).
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Illustration of "TSPM 16"

DRM: CSS, DeCSS, ...


  • Encrypt DVD (expensive key buy by microsoft for example)
  • Weak cryptography 40 bits (history)
  • Several keys (disk, titles, videos, ...)
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57 posts found