**CRYPTOGRAPHY: **The art of mathematics and secret codes, evolved with human beings’ secrets and wars. To illustrate the scope and diversity of this art, this brief article of cryptography explains a theory of hiding information, and trends arising from new technologies of it, following by example to understand more and give an in-depth study of the theory and its context..

Security is the other side of cryptography. If you want to secure information or a secret data, you must encrypt it, and the access to the encrypted data can only be done (decrypted) by the one who has the access codes. However, in some rare cases the security can be cracked by intruders (hackers and crackers).

**Cryptography Principles:** In each encryption, we have to define our ensemble that we intend work on, and we have to choose a method to encrypt our information.

**What is encryption? **Turning the “text” into “text_cipher” to be a garbled stream of characters and supposed to become non-understandable or different from the original text. In the end, a piece of information called a “key” is used to get it back to the original state using the method of “decryption”.

**What is decryption? **Turning the “text cipher” into “text decrypt” to get back as the original text. The key is an algorithm that undoes the work of the encryption algorithm. Considering most of the situations the “key” is indispensable to decrypt, since there is a low probability that anyone, other than the receiving party who has the key, will be able to decrypt -however, mathematically speaking, we cannot say impossible, yet a low probability of happening- or access to part of the original text using crypt-analysis which is a method of decryption that uses an index of different possible “keys”.

An example: we have ALICE wants to send a message to BOB, they have the algorithm of “key” between them, the group that we will work on, is from the English alphabet, A=1,B=2,,,,,Z=26..

“alice text ” ⟹ encrypt = “alice encrypt” ⟹ send to bob – then bob receives and decrypts the message using “key algorithm” = “alice decrypt”

We should note that “alice text” and “alice decrypt” must be same in the end of operation.

Let’s give more detail: the algorithm “key” is the function ” y=x+3″ and we define our group English alphabet, so we have modulo 26[number of English alphabet], and ALICE message is :”RUN”, in English alphabet the order number of the letters is “18 21 14”

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |

1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 1 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 |

By applying the equation y=x+3 ex: x= (R=18)+3, x=(U=21)+3, x= (N=14)+3 ⟹ encrypt “21 24 17” then if we link the obtained numbers to their respective order of letters it gives us “U X Q”.

⟹ BOB receives “U X Q” = “21 24 17”. By using the “key: x=y-3” ex: x= (U=21)-3, x=(X=24)-3, x= (Q=17)-3 , the numbers “21 24 17” ⟹ “18 21 14” = “RUN”.

This example is just a simple explanation, in reality the methods of encryption are more complex.

In recent years, a controversy has arisen over the so-called strong encryption. This refers to ciphers that are essentially unbreakable without the decryption keys.

Encryption is everywhere today. Every time you bank or buy something on-line or even in papers, when you make a call by your phone or when your key fob opens your car or if you watch TV,Cryptography may be out there without you knowing.

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## 3 Comments

hamza adelC bien

Hanane Menzel Ghrabathat was just amazing …. that would be so complex that it needs geniuses to solve it specially in war cases

but can i know the inventor of this method ?

حمزة رفيقYes, this method i explained with name “Caesar Cipher”‘

“chiffrement par décalage”, “تشفير عبر التحريك” شفرة سيزار

its old, a very old method

Infact, in war world II that encryption used very large and build many machines to help like enigma, but it was a simple does need a really geniuses to solve it, just read about how the allies manage to end the war across gaining the info derived from the encryption information, a little time and just some idea to crack it compared to our methods in these days, now the methods are somehow more complex than the human brain can understand or explain it to others people.