Initial commit

Encryption and Decryption for a single int block implemented.

.gitignore

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+/target

Cargo.lock

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+# It is not intended for manual editing.
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Cargo.toml

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+[package]
+name = "false-bottom"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+rand = "^0.8.5"
+modinverse = "0.1.1"

src/errors.rs

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+#[derive(Debug)]
+pub enum FalseBottomError {
+    IntegerTooLarge,
+    NoModInverse,
+    InvalidKey,
+}

src/lib.rs

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+pub mod errors;
+
+use rand::Rng;
+use rand::seq::IteratorRandom;
+use crate::errors::FalseBottomError;
+use modinverse::modinverse;
+
+#[derive(Debug)]
+pub struct FalseBottom {
+    pub k: i32,
+    pub r: Vec<i32>,
+    pub c: Vec<i32>,
+}
+
+#[derive(Debug)]
+pub struct FalseBottomKey {
+    pub key_indices: Vec<i32>,
+    pub cipher_indices: Vec<i32>,
+}
+
+const P: i32 = 9973;
+
+impl FalseBottom {
+    pub fn init(k: i32) -> FalseBottom {
+	let mut rng = rand::thread_rng();
+	let mut r: Vec<i32> = Vec::new();
+	let mut c: Vec<i32> = Vec::new();
+	for _ in 0..k {
+	    r.push(rng.gen_range(1..k));
+	    c.push(rng.gen_range(1..P));
+	}
+	FalseBottom {k, r, c}
+    }
+
+    pub fn add(&mut self, m: i32) ->
+	Result<FalseBottomKey, FalseBottomError>
+    {
+	if m > P as i32 {
+	    return Err(FalseBottomError::IntegerTooLarge)
+	}
+	let mut rng = rand::thread_rng();
+	let n = rng.gen_range(2..=self.k);
+
+	let mut cipher_indices: Vec<i32> = (0..self.c.len() as i32)
+	    .choose_multiple(&mut rng, n as usize - 1);
+	
+	let key_indices: Vec<i32> = (0..self.k)
+	    .choose_multiple(&mut rng, n as usize);
+
+	let mut sum = 0;
+	for (j, rho) in cipher_indices.iter()
+	    .zip(key_indices.iter())
+	{
+	    sum += self.c[*j as usize] * self.r[*rho as usize];
+	    sum %= P;
+	}
+
+	let key_last_el = *key_indices.last().unwrap() as usize;
+	let mod_inv = modinverse(self.r[key_last_el], P)
+	    .ok_or(FalseBottomError::NoModInverse)?;
+	let cipher_new_element = ((m - sum) * mod_inv)
+	    .rem_euclid(P);
+	self.c.push(cipher_new_element);
+	cipher_indices.push(self.c.len() as i32 - 1);
+	Ok(FalseBottomKey {key_indices, cipher_indices})
+    }
+
+    pub fn decrypt(&self, indices: &FalseBottomKey) -> Result<i32, FalseBottomError> {
+	let keyi = &indices.key_indices;
+	let cipheri = &indices.cipher_indices;
+	if keyi.len() > self.r.len() || cipheri.len() > self.c.len() {
+	    return Err(FalseBottomError::InvalidKey)
+	}
+	let mut m: i32 = 0;
+	for (ki, ci) in keyi.iter().zip(cipheri.iter()) {
+	    m += self.c[*ci as usize] * self.r[*ki as usize];
+	    m %= P;
+	}
+	Ok(m)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn encrypt_decrypt_100() {
+	let msg = 100;
+	let mut fb = FalseBottom::init(9);
+	let key = fb.add(msg).unwrap();
+	let decrypted = fb.decrypt(&key).unwrap();
+        assert_eq!(decrypted, msg);
+    }
+}

src/main.rs

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+//use false_bottom::FalseBottom;
+
+fn main() {
+    
+}