Easy explanation of what is Cryptography

Cryptography or cryptology is about securing our information from the third party to access. The best examples from which you can understand this are Bitcoin(or Cryptocurrency)  and Whatsapp end-to-end encryption. Cryptography is not only related to modern world technology or computers, but we have also been using it for thousands of years, it’s an art. So, In this article, I will try to give you a basic knowledge of cryptography, because it’s not a small topic, it's very broader and even you can do a Ph.D. in it.

Following are the pieces in which I will try to explain:

• Encryption and Decryption.
• What exactly is a key in Cryptography?

1. Encryption and Decryption.

Cryptography is done in two phases and they are encryption and decryption.
 
Encryption-
In this phase, we secure our information(or text) using a specific algorithm where we use a key to do it. I will explain it later that what is a key?. After encryption, we get our text in the secured form and that text is called encrypted or ciphertext. The text which we used to encrypt(or secure) is called plain text. Ciphertext cannot be read by any person, because it looks like this mF7pbjQxnda3hHOlCgo0sHZdFf+k8yCcEpeeYUTsk/I=, by the way, it's an encrypted form of Calloftechies.

Decryption-
Using encryption we secure our text to send it to another person so that no one can read the text except you and that person. But if you send text to someone like this- mF7pbjQxnda3hHOlCgo0sHZdFf+k8yCcEpeeYUTsk/I=
how can he/she read it?. To read real information he/she has to convert it(ciphertext) back to normal or plain text using the key and this process is called decryption.

2. What exactly is key in Cryptography?

In real life, a key is something which can be used to lock and unlock the lock. The same concept is used here, encryption is like lock and decryption is like unlock. There are two types of key algorithms are used in cryptography-

• Symmetric key- These type of algorithms use the same key to encrypt(lock) and decrypt(unlock). Vigenere and AES are examples of Symmetric key algorithms.

• For more security, some algorithms use different-different keys to encrypt and decrypt the text and these type of algorithms are called Asymmetric key algorithms. 

Key size: Strength of our cipher or encrypted text depends on key size. If the strength of our key is not good then out ciphertext can be cracked. There is three standard of key sizes- 128 bit, 192 bit and 256 bit. 256 bit is most secure key size. Now one question should rise in your mind that what is mean by 128 bit or 256 bit?.
    For example, 256-bit encryption, 256-bit encryption means if it is in binary then there will be 256 binary numbers(0 or 1) in that binary number. Almost no one can crack 256-bit encryption, because there will be 2256 possible combinations for the key and there is no computer or supercomputer which can try that number of combinations to crack. If you think 256 is just a simple number then you can see below:
2^256=115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,640,564,039,457,584,007,913129,639,936
Lol, It will take millions of years to crack.

I think now you can guess how government and companies secure their data.

If you have question in more deep then please ask me comments, I am always here to discuss.