Understanding Cryptography

In the first chapter of our series analysing the relationship between quantum computing and blockchain, you will learn about:

  • the basics of cryptography,
  • encryption algorithms
  • and why they are important in the everyday lives of us all.

Let the journey begin.

Cryptography basics

Cryptography is a cornerstone of today’s world. In its most primitive form cryptography refers to the act of using codes to protect data, information, and communication so that only those for whom the information is supposed to reach can access, decipher, and eventually utilize as it they see fit.


Over time, our communication and data storage tools evolved. So did the need to create a more robust and efficient framework for protecting data. Thus, modern cryptography was born.

What is cryptography?

Modern cryptography employs a combination of complex and sophisticated mathematical equations called algorithms and their corresponding keys to encrypt and decrypt data.

Encryption refers to the process by which data is run through a certain algorithm in order to produce what seems like a jumble of useless or unintelligent data to an onlooker. Without the corresponding secret key, which the recipient uses to unlock the data and access the data in its raw and legible form, the data is inaccessible.

Encryption vs. Decryption

“The process of converting the information from ‘plain text’ to ‘cipher text’ is known as ‘encryption.’ On similar lines, the process of converting ‘cipher text’ to ‘plain text’ is decryption.”

The algorithm employed by the sender to convert the plain text into the obscured data and the key used by the recipient are components of the same cryptosystem. In the context of cryptography, a cryptosystem refers to the set of cryptographic algorithms needed to implement a particular security outcome. Generally, a cryptosystem is comprised of three algorithms. The first is employed to generate the key while the last two for encryption and decryption respectively.

Encryption algorithms

Encryption algorithms typically fall into either of two types:

  1. symmetric
  2. asymmetric algorithms.

Symmetric algorithms employ separate instances of the same key to encrypt and decrypt the data. These algorithms are typically faster than their asymmetric counterparts. However, they fall short in terms of key distribution and key management. The parties using symmetric algorithms must be able to transmit the key confidentiality or the cryptosystem is compromised. Moreover, as the number of users grows so do the number of keys, which creates a new problem of how to securely store and manage the keys.


In asymmetric encryption, the sender and the recipient use different keys to encrypt and decrypt messages. The public key is used to encrypt the message, and the private key is used to decrypt the message. The public keys are generally made public information while the private key is reserved only for the recipient. However, it is important to note that they are two parts of the same cryptosystem and are mathematically comparable.


Despite its relative slowness in comparison to symmetric cryptography, asymmetric cryptography upholds the security tenets of authenticity and non-repudiation. It is important to note that the recipient and sender generally have access to two different keys as a generally accepted security standard. Because the sender’s key is usually made public as a tool through which it is possible to authenticate the identity of the source as well as the integrity of the data, the recipient usually has a private key
which they use to “unlock” the data which simultaneously serves to authenticate his identity.

What is a “key”?

“Further, both the sender and the receiver have similar or different “keys” to encrypt and decrypt the message. A “key” is a “value that comprises a large sequence of random bits” (Harris 2008). The larger the key size, the more difficult will it be to crack the algorithm. The “algorithm” and the “key” are the two important components of a cryptosystem.”

Explained by the InfoSec Institute

The larger the key size,

the more difficult will it be to crack the algorithm. 

The “algorithm” and the “key”

are the two important components of a cryptosystem.

Cryptography use cases in our daily lives

In this way, cryptography is essential to our daily lives. We employ it to provide secrecy to sensitive data we are storing, ensuring that it retains its integrity both in terms of contents as well as accessibility. Additionally, cryptography helps us keep our communications secure, preserving and protecting our privacy in a wide range of interactions. Lastly, cryptography allows us to authenticate our identities where needed while still preserving our privacy and in some cases our anonymity. There are myriad use cases for cryptography in our daily lives.

1.  Keeping a secret: This is the standard use of cryptography. This is where you want to either send some information to someone else, or you want to store information in a way that prevents others from snooping your files.

a.  Secure network communication, financial, government, medical, even multiplayer games.

b.  Securely storing data on your computer, like your password keeper.

c.  Crypto-currencies make use of the algorithms for digital wallets.

2.  Proving Identity: With public-key encryption, also called asymmetric encryption, it is possible to digitally “sign” some content in a way that proves to others who created the content. Or another way identity is proven is when you attempt to connect to a server, such as your bank.


b.  Digital certificates that are used to sign programs that you run on your computer and apps that you run on your phone. It lets you know that the app you are running is what the developer created, and has not been modified.


b.  Digital certificates are used by websites to verify that they are in fact your bank, or your companies secure VPN login portal


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