Implement Vigenère Cipher

aditigupta17 commented 5 years ago

Description

Vigenère Cipher is a method of encrypting alphabetic text. It uses a simple form of polyalphabetic substitution. A polyalphabetic cipher is any cipher based on substitution, using multiple substitution alphabets .The encryption of the original text is done using the Vigenère square or Vigenère table.

The table consists of the alphabets written out 26 times in different rows, each alphabet shifted cyclically to the left compared to the previous alphabet, corresponding to the 26 possible Caesar Ciphers.
At different points in the encryption process, the cipher uses a different alphabet from one of the rows.
The alphabet used at each point depends on a repeating keyword.

Input:

A String of lower case letters, called Plain Text.
Another String of lower case letters, called Keyword.

You are expected to write a program that receives a Plain Text (string) and Keyword (string) and returns the encrypted text.

Example: Plain Text: cryptographyisfun Keyword: idoubt Cipher Text: kumjuhouojirqvtoo

Details

Technical Specifications:

Type of issue: No more than one implementation will be accepted for each language. Once the implementation for a language has been taken up (i.e if it is checked in the 'Issue Progress' section), you must choose from the remaining.
Time Limit: Issues will be given on a first-come, first-serve basis. Once you take this issue up, you must complete it within 2 days, failing which the issue will be allocated to the next person who requested for this issue.
Additional instructions: While making the Pull Request, attach screenshots of 5 sample inputs and their corresponding output.

Issue requirements / progress

[ ] C
[x] C++
[x] Python
[x] Java

Resources

https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher

Directory Structure

For this issue, use the following directory of the Hacktoberfest-2k18 repository: /systems/cryptography/vigenere-cipher/ (where language_name is one of the languages mentioned above.)