Overview of One Time Pad

One time pad is a subset of vernam cipher, implemented using a random set of non repeating characters as the input cipher text. Length of input cipher text must be equal to the length of original plain text. It is named as one time pad because once the input cipher text is used for the transmission, it is never used again for any other message i.e. input cipher text is discarded after a single use, hence it is used for the short message. For example, the one time password we use for secure transmission.

What is One Time Pad?

One-time-pad is a system that generates a randomly organized and unique ‘private key’, this one time use private key is used to encrypt a message which later on is decrypted by the receiver with the use of matching one-time-pad and key. Information encrypted with keys is almost impossible to break. Each encryption is unique and shows no relation with other encryption. In one-time-pad, the key used is known as a secret key as they hold a very crucial piece of pieces of information.

Understanding of One Time Pad

To understand one-time-pad we must focus on the encryption process, to see how things work. This will help us understand the one-time-pad in a better way. The encryption process is crucial to understand, in this, some keys are used in pairs. Each user has their copy of the key which is distributed securely before the encryption process. Since the One-time-pad keys are highly confidential so they are assured by highly continuous protection during the storage and distribution phase.

There are a combination and variation of XOR associated with the entire encryption process. Let us see how things work at ground level –

While encrypting any plain text data, the sender uses a key string that has a similar length to the text. This key is used by mixing (XOR-ing) bit by bit. The bit by bit mixing means a bit of ‘key’ with a bit of ‘plain text’ to create a bit of ‘ciphertext’.
This ciphertext is then forwarded to the recipient.
At the recipient end, the encoded message is mixed with the duplicate copy (XOR-ed) of One-time key and the plain text is restored. After this, the keys that belong to the sender’s and recipients are destroyed automatically. This makes sure that no re-application and usage of the same is possible.

How Does One Time Pad work?

At its core, a one-time-pad system holds a ‘random key’. This random key is a block or collection of numbers that is used to transform the original message.

Note – The Original Message is called Plaintext.

Coded text is called a Ciphertext. So, first, you have to create ‘random key’ and to do this you need a ‘method’ to convert alphabets into numbers.

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Follow the below-mentioned conversion table chart –

For Example, your message is: ASFKHRGQLRIUGQLFHT

1) To make an easier and effective approach we have to break it into a set of two characters, let see how –

AS, FK, HR, GQ, LR, IU, GQ, LF, HT

2) Follow the above-mentioned conversion table chart – we have something like this.

AS, FK, HR, GQ, LR, IU, GQ, LF, HT = 0119, 0611, 0818, 0717, 1218, 0921, 0717, 1206, 0820

3) So finally, the text “ASFKHRGQLRIUGQLFHT” got converted to “0119 0611 0818 0717 1218 0921 0717 1206 0820”

Principles

There is a basic principle underlying the working of ‘Cryptography’ and ‘One-time-pad’. Kerckhoff’s principle of cryptography was born in Netherland by Auguste Kerckhoff in the 19^th century. This principle forms the fundamental of open security, security by design. “The design of a system should not require secrecy”.

What can you do with One Time Pad?

The one-time pad can be used for superencryption.
It can be apart of an introduction to cryptography.
It is mimicked by stream ciphers.
It is the most sought out options in a situation where two separate environments are considered with complete secrecy.

Advantages and disadvantages

Let us see some of the Advantages and Disadvantages of One Time Pad:

Advantages–

This device is completely unbreakable.
It is secured as it can be used only once.
Each byte in one-time-pad is having any connection to another byte of the ley.

Disadvantages–

Exchange of the one-time-pad.
The ‘key’ is as long as the ‘message’.
Links for disadvantages in detail – Coursera.

Uses of One Time Pad:

Confidentiality: One of the prime reasons will be ‘Confidentiality’. One-Time-Pad users understand this as the messages and transcripts are secured form others.
Integrity: The information is uniform and cannot be altered or changed either in storage or while transmission. The sender and intended receiver will get prior information about the changes if someone tries to.
Non-repudiation: The sender and creator of the information cannot deny to their intention of creation or transmission of the information.
Authentication: Both the sender/receiver can claim his/her identity with the origin/destination of the information.

What is the need for One Time Pad?

The need of the one-time-pad lies with the:

Defense (across the globe).
Security personnel.
Spies and
Several other confidential agencies.

Also, with the users who want to communicate with keeping privacy in mind.

Conclusion

We have come across some crucial facts about the ancient science of cryptography and one-time-pad. How this encryption technique has helped society in the need for safe information communication. Since every coin has two faces, the technology of one-time-pad is no different as it has bot usefulness and drawbacks associated with it.