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One Time Pad Cipher in Cryptography
This article is about the encryption technique: first, One Time Pad Cipher. In this article, we will first have a brief introduction regarding this technique and then will look into how the encryption and decryption are performed in it?
Submitted by Monika Sharma, on January 17, 2020
The One-time Pad cipher is almost similar to the Vernam cipher, as, like the vernam cipher, this cipher technique also encrypts the plain text by working on the binary level of the text. The only difference between the two is that the length of the key in the Vernam Cipher must be less than or equal to the length of the plain text, whereas, in One-time pad Cipher, the length of the key must be equal to that of the Plain text. It cannot be less than that.
Now, talking about its characteristics and details, One-time pad cipher is a cipher in which we consider both the plain text and the key string in its binary form.
The following key points can be drawn for the One Time Pad cipher,
- The key chosen here is a string whose length must be equal to the length of the plain text.
- The key can be either in string form or directly in binary form also.
- It is a type of symmetric-key cryptography.
- It is a type of poly-alphabetic cipher, being a part of the substitution cipher.
Encryption Process
Decryption Process
The process of decrypting the ciphertext to convert it back into plain text is performed in the same way as the encryption process. Therefore, the formula for decryption of the text under Vernam cipher is as follows,
D (C_{i} , K_{i}) = C_{i} (XOR) K_{i}
Example Problem
Given Plain text: IF
Key: 1101011 0101111
Convert the given plain text into cipher text...
Solution:
Note: You can cross-check your answer by applying the decryption process over the ciphertext, and if it comes back to be the same as the plain text, then it means that our answer is correct.
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