Question: Using C++, write a program to implement the Vigenre cipher. important: Please create a class for the letters to do the overload, like: class Letter
Using C++, write a program to implement the Vigenre cipher.
important: Please create a class for the letters to do the overload, like:
class Letter {
public:
friend Letter operator+(const Letter &lhs, const Letter &rhs);
private:
char c;
};
Then use a vector of Letter to store the plaintext/ciphertext/key.
Vonvert between this and a std::string, loop through each element and convert.
a actor of Letter that takes a char to getter to go back to a string.
Example of pseudocode:
Letter to offset:
if (isupper(letter)) {
return letter - A
} else {
return letter - a
}
To encrypt a single letter (this should be part of the overloaded + operator):
ciphertext_offset = (letter_to_offset(plaintext_letter) + letter_to_offset(key_letter)) % 26
if (isupper(plaintext_letter)) {
return ciphertext_letter + A
} else {
return ciphertext_letter + a
}
To decrypt a single letter (this should be part of the overloaded - operator):
plaintext_offset = (letter_to_offset(ciphertext_letter) - letter_to_offset(key_letter) + 26) % 26
if (isupper(ciphertext_letter)) {
return plaintext_offset + A
} else {
return plaintext_offset + a
}
To encrypt a string:
key_letter = 0
for each character c of the plaintext {
if (c is not an alphabetic character) {
ciphertext += c
} else {
ciphertext += c + key[key_letter]
++key_letter
key_letter %= key.length()
}
}
To decrypt a string:
key_letter = 0
for each character c of the ciphertext {
if (c is not an alphabetic character) {
plaintext += c
} else {
plaintext += c - key[key_letter]
++key_letter
key_letter %= key.length()
}
}
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Plaintext: How vexingly quick daft zebras jump! Key: KEY KEYKEYKE YKEYK EYKE YKEYKE YKEY Ciphertext: Rsu fivsrevc oemau hypx xofpkw heqn!
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