67 posts found

Illustration of "Cryptology"

Cryptology embraces two branche: Cryptanalysis & Cryptography

6 mains concepts of cryptography:

  • Confidentiality/Secrecy: Only the destination can read the message
  • Authentication: The destination can be sure the message is sent by the sender
  • Integrity: The message cannot be changed during the transmission
  • Source nonrepudiation: The source cannot deny sending the message
  • Destination nonrepudiation: The destination cannot deny receiving the message
  • Signatures: Third parties can be sure that the message is sent by the sender
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Illustration of "Number, bases. How to convert decimal, hexadecimal and binary ?"


A base is a set of symbols (digits) that can be used to represent a value (number).

  • Decimal base = 0 1 2 3 4 5 6 7 8 9
  • Hexadecimal base = 0 1 2 3 4 5 6 7 8 9 A B C D E F (a = 10, b = 11, ...)

The significance of each digit depends on its position (power of N, where N is the number of digits in the base).

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Illustration of "Data security"


Security is Confidentiality, Integrity, Availability, Authentication, Nonrepudiation.

The assets must be protected (Physical support, Files, Software). Furthermore, network must be secured too because the data must be protected during the transmission itself.

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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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67 posts found