Having learned about cryptography in the previous article, it is now time to learn about the types of cryptography. You are right, nothing is complete till we understand its types and subtypes and so on. Remember, your best friends, Alice and Bob!!! They are going to help us understand the types of cryptography.

Before we go into the details, we ought to recapitulate a few terms.

1.

**Plain text**– Data in a readable or understandable format.
2.

**Ciphertext**– Random and unreadable text
3.

**Encryption**– Process of converting plain text into cipher text.
4.

**Key**– Sequence of random bits
5.

**Algorithm**– Rules by which encryption and decryption will take place.
It is really important to clearly understand these terms, else, the journey ahead will be difficult. So lets us begin.

Cryptography algorithms are either symmetric algorithms, which use symmetric keys (also called secret keys), or asymmetric algorithms, which use asymmetric keys (also called public and private keys). I know, this can be confusing, if you read this the first time, however, you’ll be able to sail through if you pay close attention.

If you and I share the same password, we are using the symmetric algorithm and if we use a public and a private password, we are using the asymmetric algorithm. This is not technically correct, however, explains it in a manner that you can understand.

**Symmetric Algorithm**

Alice and Bob, as usual, want to communicate with each other. Alice has an old age secret recipe of pancakes which Bob has requested from Alice. Given the current scenario of data breaches happening everywhere, Alice is skeptical of sending it as such. She discusses with Bob and they both decide to use symmetric cryptography for this purpose. In a cryptosystem that uses symmetric cryptography, the sender and receiver use two instances of the same key for encryption and decryption. This means that if Alice uses the key “123@encrypt” for encrypting, Bob will also use the same key to decrypt it. Each pair of users who want to exchange data using symmetric key encryption must have two instances of the same key.

The diagram below also illustrates the same.

Clearly, in symmetric encryption, it is the secrecy of the key that plays the most important role. If 3 people wish to communicate with each other, all 3 must have the same key and most importantly, all 3 of them must keep it secret. Hence, keeping the key secret is a big task, if there are many people involved.

We had learned that cryptography helps us achieve confidentiality. Symmetric cryptography can help us achieve that, but, can it help us achieve integrity, non-repudiation or authentication? Think for a minute. What is integrity? No unauthorized modification. But if the secret key is no longer secret, you cannot be 100% sure that no modification has taken place. There is also no way to prove who sent the message if two or three people are using the same secret key.