1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
use common::alphabet::Alphabet;
use common::cipher::Cipher;
use common::keygen::concatonated_keystream;
use common::{alphabet, substitute};
pub struct Autokey {
key: String,
}
impl Cipher for Autokey {
type Key = String;
type Algorithm = Autokey;
fn new(key: String) -> Autokey {
if key.is_empty() {
panic!("The key must contain at least one character.");
} else if !alphabet::STANDARD.is_valid(&key) {
panic!("The key cannot contain non-alphabetic symbols.");
}
Autokey { key }
}
fn encrypt(&self, message: &str) -> Result<String, &'static str> {
Ok(substitute::key_substitution(
message,
&concatonated_keystream(&self.key, message),
|mi, ki| alphabet::STANDARD.modulo((mi + ki) as isize),
))
}
fn decrypt(&self, ciphertext: &str) -> Result<String, &'static str> {
let mut plaintext = String::new();
let mut keystream: Vec<char> = self.key.clone().chars().collect();
let mut stream_idx: usize = 0;
for ct in ciphertext.chars() {
let ctpos = alphabet::STANDARD.find_position(ct);
match ctpos {
Some(ci) => {
let mut decrypted_character: char;
if let Some(kc) = keystream.get(stream_idx) {
if let Some(ki) = alphabet::STANDARD.find_position(*kc) {
let si = alphabet::STANDARD.modulo(ci as isize - ki as isize);
decrypted_character =
alphabet::STANDARD.get_letter(si, ct.is_uppercase());
} else {
panic!("Keystream contains a non-alphabetic symbol.");
}
} else {
panic!("Keystream is not large enough for full substitution of message.");
}
plaintext.push(decrypted_character);
keystream.push(decrypted_character);
stream_idx += 1;
}
None => plaintext.push(ct), }
}
Ok(plaintext)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn with_utf8() {
let m = "Attack 🗡️ the east wall";
let a = Autokey::new(String::from("fort"));
assert_eq!(m, a.decrypt(&a.encrypt(m).unwrap()).unwrap());
}
#[test]
fn simple_encrypt_decrypt_test() {
let message = "defend the east wall of the castle";
let v = Autokey::new(String::from("fortification"));
let c_text = v.encrypt(message).unwrap();
let p_text = v.decrypt(&c_text).unwrap();
assert_eq!(message, p_text);
}
#[test]
fn decrypt_test() {
let ciphertext = "lxfopktmdcgn";
let v = Autokey::new(String::from("lemon"));
assert_eq!("attackatdawn", v.decrypt(ciphertext).unwrap());
}
#[test]
fn valid_key() {
Autokey::new(String::from("LeMon"));
}
#[test]
#[should_panic]
fn key_with_symbols() {
Autokey::new(String::from("!em@n"));
}
#[test]
#[should_panic]
fn key_with_whitespace() {
Autokey::new(String::from("wow this key is a real lemon"));
}
}