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added doctest to playfair_cipher.py (#10823)

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* added doctest to playfair_cipher.py

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Anshu Sharma 2023-10-23 03:09:31 +05:30 committed by GitHub
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commit fdb0635c71
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1 changed files with 57 additions and 2 deletions
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59
ciphers/playfair_cipher.py
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@ -1,3 +1,24 @@
"""
https://en.wikipedia.org/wiki/Playfair_cipher#Description
The Playfair cipher was developed by Charles Wheatstone in 1854
It's use was heavily promotedby Lord Playfair, hence its name
Some features of the Playfair cipher are:
1) It was the first literal diagram substitution cipher
2) It is a manual symmetric encryption technique
3) It is a multiple letter encryption cipher
The implementation in the code below encodes alphabets only.
It removes spaces, special characters and numbers from the
code.
Playfair is no longer used by military forces because of known
insecurities and of the advent of automated encryption devices.
This cipher is regarded as insecure since before World War I.
"""
import itertools
import string
from collections.abc import Generator, Iterable
@ -60,11 +81,26 @@ def generate_table(key: str) -> list[str]:
def encode(plaintext: str, key: str) -> str:
"""
Encode the given plaintext using the Playfair cipher.
Takes the plaintext and the key as input and returns the encoded string.
>>> encode("Hello", "MONARCHY")
'CFSUPM'
>>> encode("attack on the left flank", "EMERGENCY")
'DQZSBYFSDZFMFNLOHFDRSG'
>>> encode("Sorry!", "SPECIAL")
'AVXETX'
>>> encode("Number 1", "NUMBER")
'UMBENF'
>>> encode("Photosynthesis!", "THE SUN")
'OEMHQHVCHESUKE'
"""
table = generate_table(key)
plaintext = prepare_input(plaintext)
ciphertext = ""
# https://en.wikipedia.org/wiki/Playfair_cipher#Description
for char1, char2 in chunker(plaintext, 2):
row1, col1 = divmod(table.index(char1), 5)
row2, col2 = divmod(table.index(char2), 5)
@ -83,10 +119,20 @@ def encode(plaintext: str, key: str) -> str:
def decode(ciphertext: str, key: str) -> str:
"""
Decode the input string using the provided key.
>>> decode("BMZFAZRZDH", "HAZARD")
'FIREHAZARD'
>>> decode("HNBWBPQT", "AUTOMOBILE")
'DRIVINGX'
>>> decode("SLYSSAQS", "CASTLE")
'ATXTACKX'
"""
table = generate_table(key)
plaintext = ""
# https://en.wikipedia.org/wiki/Playfair_cipher#Description
for char1, char2 in chunker(ciphertext, 2):
row1, col1 = divmod(table.index(char1), 5)
row2, col2 = divmod(table.index(char2), 5)
@ -102,3 +148,12 @@ def decode(ciphertext: str, key: str) -> str:
plaintext += table[row2 * 5 + col1]
return plaintext
if __name__ == "__main__":
import doctest
doctest.testmod()
print("Encoded:", encode("BYE AND THANKS", "GREETING"))
print("Decoded:", decode("CXRBANRLBALQ", "GREETING"))