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/// Vigenere Cipher
///
/// The struct is generated through the new() function.
///
pub struct Vigenere {
key: &'static str,
}
impl Vigenere {
/// Initializes a vigenere cipher with a supplied key.
///
/// # Examples
///
/// ```
/// use kryptos::ciphers::vigenere::Vigenere;
///
/// let v = Vigenere::new("secret").unwrap();
/// ```
///
/// # Errors
///
/// Will return Err() if the key is not alphabetic.
///
pub fn new(key: &'static str) -> Result<Self, String> {
for c in key.chars() {
if c.is_alphabetic() {
continue;
}
return Err(String::from("Key must be alphabetic"));
}
Ok(Vigenere { key })
}
/// Enciphers a message with a vignere cipher.
///
/// # Examples
///
/// ```
/// use kryptos::ciphers::vigenere::Vigenere;
///
/// let v = Vigenere::new("blaise").unwrap();
/// assert_eq!(
/// "tsh ggy ilvm qsv hhqktfc",
/// v.encipher("shh you have you whisper").unwrap()
/// );
/// ```
///
pub fn encipher(&self, plaintext: &str) -> Result<String, &'static str> {
Vigenere::transpose(&self.convert_key().unwrap(), plaintext)
}
/// Deciphers a message with a vignere cipher.
///
/// # Examples
///
/// ```
/// use kryptos::ciphers::vigenere::Vigenere;
///
/// let v = Vigenere::new("blaise").unwrap();
/// assert_eq!(
/// "whispering can still be heard by others",
/// v.decipher("xsiahistno ueo dtqdp cp hmsve my wllfcs").unwrap()
/// );
/// ```
///
pub fn decipher(&self, ciphertext: &str) -> Result<String, &'static str> {
let mut filter = Vec::new();
for n in self.convert_key().unwrap() {
filter.push((26 - n) % 26);
}
Vigenere::transpose(&filter, ciphertext)
}
// Uses the converted key to perform the encipher or decipher of a message.
//
fn transpose(filter: &[u8], text: &str) -> Result<String, &'static str> {
let mut filter_index = 0;
let mut result = String::new();
for c in text.chars() {
match c as u8 {
65..=90 => {
result.push(
(((c as u8 - 65 + filter[filter_index % filter.len()]) % 26) + 65) as char,
);
filter_index += 1;
}
97..=122 => {
result.push(
(((c as u8 - 97 + filter[filter_index % filter.len()]) % 26) + 97) as char,
);
filter_index += 1;
}
_ => result.push(c),
}
}
Ok(result)
}
// Converts a key into a vector of u8.
//
fn convert_key(&self) -> Result<Vec<u8>, String> {
self.key
.chars()
.map(|c| match c as u8 {
65..=90 => Ok((c as u8 - 65) % 26),
97..=122 => Ok((c as u8 - 97) % 26),
_ => Err(String::from("Invalid character in key")),
})
.collect()
}
}
#[cfg(test)]
mod tests {
use super::Vigenere;
#[test]
fn valid_key() {
assert!(Vigenere::new("secret").is_ok());
}
#[test]
fn invalid_key() {
assert!(Vigenere::new("s3cr3t").is_err());
}
#[test]
fn key_conversion() {
let v = vec![3, 8, 5, 5, 8, 4];
let x = Vigenere::new("diffie").unwrap();
assert_eq!(v, x.convert_key().unwrap());
}
#[test]
fn invalid_key_conversion() {
assert!(Vigenere::convert_key(&Vigenere { key: "dif.fie" }).is_err());
}
#[test]
fn encipher() {
let v = Vigenere::new("blaise").unwrap();
assert_eq!(
"tsh ggy ilvm qsv hhqktfc",
v.encipher("shh you have you whisper").unwrap()
);
}
#[test]
fn with_punctuation() {
let v = Vigenere::new("blaise").unwrap();
assert_eq!(
"tsh! ggy ilvm qsv hhqktfc",
v.encipher("shh! you have you whisper").unwrap()
);
}
#[test]
fn with_unicode() {
let v = Vigenere::new("babbage").unwrap();
assert_eq!(
"Eo zpu 🖤 yidrfu mkwtahfs?",
v.encipher("Do you 🖤 secret messages?").unwrap()
);
}
#[test]
fn decipher() {
let v = Vigenere::new("blaise").unwrap();
assert_eq!(
"whispering can still be heard by others",
v.decipher("xsiahistno ueo dtqdp cp hmsve my wllfcs")
.unwrap()
);
}
}