"/home/yossef/notes/Su/security//study_security_l3.md"

path: Su/security//study_security_l3.md

- **fileName**: study_security_l3
- **Created on**: 2025-03-17 01:45:40

what is plain text?

it's the original data or text that gone fed into the algorthim for
encryption

what is the encryption algorthim?

the encryption algorthim perform various substituation and transformation
in the plain text

what is secret key?

it's a key using for the encryption operation and independent from the plain
text and if the operation and reduce the same encrypted value each with
the same key this mean algorithim is preformed by the secret key

what is the cipher text?

this is the scrambled message produced as output and it's dependce on the
the algorthim and the secrect key

what is decryption algorthim?

this is run the algorthim of encryption in reverse

what is subsititution technique?

is one which is the letters are placed with another letters or numbers or
symbols

what is transposition technique?

is one which the performing some sort and arange on the plain text letters

what is ceaser cipher(subsititution)?

the ceaser cipher is involves replacing each letter with alphabat adding the
standing k modules 26: C = E(k, p) = (p + k) mod 26

what is playfair techique(subsititution)?

it's the best known multiple encryption cipher which treats dirgrams in
plain text like single units and translate these units into ciphertext and
it's based in 5*5 matrix letters

what is hill cipher(subsititution)?

• this algorthim takes the successive plain text letters and substitutes
  for them m charachters , the subititutes determine the m linear equation
  in each charachter assign numerical value
• Hill cipher encryption is a method of encrypting messages using linear algebra,
  where each letter is represented by a number modulo 26. It involves
  multiplying blocks of letters, treated as vectors, by an invertible matrix
  (the cipher key) to produce ciphertext.

what is the vigenere cipher(subsititution)?

to encypt a message first repeating the key based on the length for the text
then convert the key and plain text ot numrical and value and adding theme
and module 26 and then convert the numerical value to letter (( c + p ) mod 26)

what is rail fence(transposition)?

the plain text is written down in diagonals and then read off as sequence row

1. so gone be like 10 / 3 = 3.333333333
2. so now there is 3 and some float numbers what i want now i 3 in the first
   3.3333333 = now there is 3 of 3 in the 10 ,3 and 3 and 3 and 1 = 10
3. so the new eqution gone be (10 / 3 - 3) = .33333333
   now the number .33333 the value of module that in 10 is (1)
4. so for this now multiply .3333333 * module(3) and get the number 1
   this is the module

more information: calc module

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