Cryptography and Cryptanalysis

30 Sep 2017

Cryptography and Cryptanalysis

Cryptography is a method to secure your communication in the presence of third parties. Cryptography usually changes the letter with pre-defined code or using algorithm and math to create the new code. For the simple example, we have the calculation of alphabet ASCII and want to secure the communication by increasing the alphabetic ASCII. Then when we communicate, we will encrypt the alphabet and increase the ASCII by the number we have decided.

If we do this, there would be a trouble for people who don’t know what the algorithm we use to encrypt those codes. This could secure the word and only those who know the algorithm will understand the code. For a simple example, we determined the codes will encrypted by increasing the ASCII by three. For the algorithm could be seen below.

Then, if encrypt ‘A’, it will become ‘D’’

But again, this is just a simple kind of cryptography.

As for Cryptanalysis, Cryptanalysis is a method or process to find a weakness in cryptographic algorithm and using the weakness to decrypt / decipher the code or the secret key. Usually cryptanalysis used to decode and discover how the cryptography algorithms work. Like the first time when you get a code, you will do the analysis for the code and discover what kind of algorithm it uses.

There are a various types of cryptanalysis, based by amount and qualities of secret information are discovered:

  • Total Break

The attacker deduces the secret key (fully discover about the algorithm and the secret code mean)

  • Global deduction

The attacker more likely to know about the algorithm or the equivalent algorithm it used, but they didn’t discover what the secret code means

  • Information Deduction

The attacker could gain some information about the secret code, but didn’t discover how the algorithm works

  • Distinguishing algorithm

The attacker has the ability to discover how the encryption works and could distinguish the output for a different permutation

 

Source:

https://en.wikipedia.org/wiki/Cryptography

https://www.owasp.org/index.php/Cryptanalysis

https://en.wikipedia.org/wiki/Cryptanalysis