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
|
extern crate "rustc-serialize" as serialize;
use std::ascii::AsciiExt;
use std::num::Float;
use serialize::base64::{ToBase64,STANDARD};
const ENGLISH_FREQUENCIES: [f64; 26] = [
0.0804,
0.0148,
0.0334,
0.0382,
0.1249,
0.0240,
0.0187,
0.0505,
0.0757,
0.0016,
0.0054,
0.0407,
0.0251,
0.0723,
0.0764,
0.0214,
0.0012,
0.0628,
0.0651,
0.0928,
0.0273,
0.0105,
0.0168,
0.0023,
0.0166,
0.0009,
];
pub fn to_base64 (bytes: &[u8]) -> String {
return bytes.to_base64(STANDARD);
}
pub fn fixed_xor (bytes1: &[u8], bytes2: &[u8]) -> Vec<u8> {
return bytes1.iter()
.zip(bytes2.iter())
.map(|(&a, &b)| { a ^ b })
.collect();
}
pub fn repeating_key_xor (plaintext: &[u8], key: &[u8]) -> Vec<u8> {
return fixed_xor(
plaintext,
&key
.iter()
.cycle()
.take(plaintext.len())
.map(|c| *c)
.collect::<Vec<u8>>()[..]
);
}
pub fn crack_single_byte_xor (input: &[u8]) -> Vec<u8> {
let (key, _) = crack_single_byte_xor_with_confidence(input);
return repeating_key_xor(input, &[key]);
}
pub fn find_single_byte_xor_encrypted_string (inputs: &[Vec<u8>]) -> Vec<u8> {
let mut min_diff = 100.0;
let mut best_decrypted = vec![];
for input in inputs {
let (key, diff) = crack_single_byte_xor_with_confidence(input);
if diff < min_diff {
min_diff = diff;
best_decrypted = repeating_key_xor(input, &[key]);
}
}
return best_decrypted;
}
fn hamming (bytes1: &[u8], bytes2: &[u8]) -> u64 {
count_bits(&fixed_xor(bytes1, bytes2)[..])
}
fn count_bits (bytes: &[u8]) -> u64 {
bytes.iter().map(|&c| { count_bits_byte(c) }).fold(0, |acc, n| acc + n)
}
fn count_bits_byte (byte: u8) -> u64 {
(((byte & (0x01 << 0)) >> 0)
+ ((byte & (0x01 << 1)) >> 1)
+ ((byte & (0x01 << 2)) >> 2)
+ ((byte & (0x01 << 3)) >> 3)
+ ((byte & (0x01 << 4)) >> 4)
+ ((byte & (0x01 << 5)) >> 5)
+ ((byte & (0x01 << 6)) >> 6)
+ ((byte & (0x01 << 7)) >> 7)) as u64
}
fn crack_single_byte_xor_with_confidence (input: &[u8]) -> (u8, f64) {
let mut min_diff = 100.0;
let mut best_key = 0;
for a in 0..256u16 {
let decrypted = fixed_xor(
input,
&std::iter::repeat(a as u8)
.take(input.len())
.collect::<Vec<u8>>()[..]
);
if !decrypted.is_ascii() {
continue;
}
let lowercase = decrypted.to_ascii_lowercase();
let mut frequencies = [0; 26];
let mut total_frequency = 0;
for c in lowercase {
if c >= 0x61 && c <= 0x7A {
total_frequency += 1;
frequencies[(c - 0x61) as usize] += 1;
}
}
let mut total_diff = 0.0;
for (&english, &crypt) in ENGLISH_FREQUENCIES.iter().zip(frequencies.iter()) {
let relative_frequency = (crypt as f64) / (total_frequency as f64);
total_diff += (english - relative_frequency).abs();
}
if total_diff < min_diff {
min_diff = total_diff;
best_key = a as u8;
}
}
return (best_key, min_diff);
}
#[test]
fn test_hamming () {
assert_eq!(hamming(b"this is a test", b"wokka wokka!!!"), 37);
}
|
