Updated July 3, 2023
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. The length of input ciphertext must be equal to the length of the original plain text. It is named a one-time pad because once the input ciphertext is used for the transmission, it is never used again for any other message, i.e. input ciphertext is discarded after a single use is used for the short message. For example, the one-time password we use for secure transmission.
What is a One Time Pad?
It is a system that generates a randomly organized and unique ‘private key’; this one-time use private key is used to encrypt a later decrypted message by the receiver using a 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
To understand the 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 a copy of the key, which is distributed securely before the encryption process. 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 variations 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 the 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.
Coded text is called a Ciphertext. First, you have to create a ‘random key’ and to do this; you need a ‘method’ to convert alphabets into numbers.
Follow the below-mentioned conversion table chart:
| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | |
| 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | |
|
|
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 19th 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 a part of an introduction to cryptography.
- Stream ciphers mimic it.
- It is the most sought-out option in a situation where two separate environments are considered complete secrecy.
Advantages and disadvantages
Let us see some of the Advantages and Disadvantages below:
Advantages
- This device is completely unbreakable.
- It is secured as it can be used only once.
- Each byte in a 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
- Confidentiality: One of the prime reasons will be ‘Confidentiality’. One-Time-Pad users understand this as the messages and transcripts are secured from 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 their intention to create or transmit the information.
- Authentication: Both the sender/receiver can claim his/her identity with the origin/destination of the information.
Need
The need for 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 the one-time-pad how this encryption technique has helped society in need of safe information communication. Since every coin has two faces, the one-time-pad technology is no different as it has both usefulness and drawbacks associated with it.
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