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+---- Thread: FastC4 - Cipher alg made in rust with pseudocode included (/showthread.php?tid=6293521)
FastC4 - Cipher alg made in rust with pseudocode included - derfdo716 - Mar 2, 2025
This is a very simple cipher I designed in the rust language.
I wrote pseudocode for it as well which would make it very easy to translate into another language.
I would believe that security wise, this is similar to RC4 however it is at least 2x slower than RC4 as there are 2 iterations of the main cipher function called.
Like RC4 it also allows for an arbitrary sized key, in this cipher it must be at least 2 bytes of size.
Code
pub struct FastC4 {
state: Vec<u8>,
len: usize
}
impl FastC4 {
pub fn new(key: &Vec<u8>) -> FastC4 {
if key.len() <= 1 {
panic!("Key is too small");
}
FastC4 {
state: key.clone(),
len: key.len()
}
}
fn routine(&mut self, data: &mut Vec<u8>) {
let mut temp: u8 = 0x41;
/*
S = [...]
D = [...]
L = Len S
T = 65
for I = 0 to Len D - 1 {
J = I mod L
K = ~I mod L
D[I] = D[I] ⊕ S[J]
S[J] = (S[J] + S[K] + T) ∧ 0xff
T = T ⊕ S[J]
S[K] = (S[K] - S[J]) ∧ 0xff
}
*/
for i in 0..data.len() {
let j = i % self.len;
let k = (!i) % self.len;
data[i] ^= self.state[j];
self.state[j] = self.state[j].wrapping_add(self.state[k]).wrapping_add(temp);
temp ^= self.state[j];
self.state[k] = self.state[k].wrapping_sub(self.state[j]);
}
}
fn apply_cipher(&mut self, data: &mut Vec<u8>) {
let original_state = self.state.clone();
self.routine(data);
for i in 0..self.len { self.state[i] ^= original_state[(self.len - i) % self.len]; }
self.routine(data);
self.state = original_state; // Restore the state so that the decrypt operation can be performed
}
pub fn encrypt(&mut self, data: &mut Vec<u8>) { self.apply_cipher(data); } // The cipher encrypt function is also the decrypt function
pub fn decrypt(&mut self, data: &mut Vec<u8>) { self.apply_cipher(data); }
}