Initial commit

.gitignore

@@ -0,0 +1,3 @@
+/target
+**/*.rs.bk
+Cargo.lock

Cargo.toml

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+[package]
+name = "secretsharing"
+version = "0.1.0"
+authors = ["pawanjay176 <[email protected]>"]
+edition = "2018"
+
+[dependencies]
+rand = "0.6"

src/main.rs

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+mod utils;
+
+
+fn main() {
+    println!("Hello, world!");
+    println!("{:?}", utils::modinv(-18, 13));
+    println!("{:?}", utils::random_polynomial(10, 50, 41));
+    println!("{:?}", utils::mod_lagrange_interpolation(vec![(1,2), (3,4), (5,6)], 100));
+}

src/utils.rs

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+extern crate rand;
+
+use rand::Rng;
+
+pub fn egcd(a: i64,b: i64) -> (i64, i64, i64) {
+    if a == 0 {
+        (b, 0, 1)
+    }
+    else {
+        let (gcd, x, y) = egcd(b % a, a);
+        (gcd, y - (b/a) * x, x)
+    }
+}
+
+pub fn modinv(a: i64, prime: i64) -> Option<i64> {
+    let (gcd, x, _) = egcd(a, prime);
+
+    if gcd != 1 {
+        None
+    }
+    else {
+        Some(((x % prime) + prime) % prime)
+    }
+}
+
+pub fn random_polynomial(degree: i64, intercept: i64, upper_bound: i64) -> Vec<i64> {
+    let mut coeff = vec![intercept];
+    let mut rng = rand::thread_rng();
+    for _ in 0..degree {
+        let c = rng.gen_range(0, upper_bound);
+        coeff.push(c);
+    }
+    coeff
+}
+
+
+pub fn get_polynomial_points(coeff: Vec<i64>, num_points: i64, prime: i64) -> Vec<(i64, i64)> {
+    let mut points: Vec<(i64, i64)> = Vec::new();
+    for i in 1..=num_points {
+        let mut y = coeff[0];
+        for j in 1..coeff.len() {
+            let exp: i64 = (i.pow(j as u32)) % prime;
+            let term = (coeff[j] * exp) % prime;
+            y = (y + term) % prime;
+        }
+        points.push((i,y));
+    }
+    points
+}
+
+pub fn mod_lagrange_interpolation(points: Vec<(i64, i64)>, prime: i64) -> i64 {
+    let mut res: i64 = 0;
+    let x_values: Vec<i64> = points.iter().map(|(x, _)| *x).collect();    
+    let y_values: Vec<i64> = points.iter().map(|(_, y)| *y).collect();
+    for i in 0..points.len(){
+        let mut num: i64 = 1;
+        let mut den: i64 = 1;
+        for j in 0..points.len(){
+            if i == j {
+                continue
+            }
+            else {
+                num = (num * -x_values[j]) % prime;
+                den = (den * (x_values[i] - x_values[j])) % prime;
+            }
+        }
+        let lagrange_polynomial = num * modinv(den, prime).unwrap();
+        res = (res + prime + (y_values[i] * lagrange_polynomial)) % prime;
+    }
+    res
+}
+
+pub fn int_to_charset(val: u64, charset: String) -> String {
+    if val == 0 {
+        charset.chars().nth(0).unwrap().to_string()
+    }
+    else {
+        let mut res = String::new();
+        let mut value = val.clone();
+        while value > 0 {
+            value = value / charset.len() as u64;
+            let digit = value % charset.len() as u64;
+            res.push(charset.chars().nth(digit as usize).unwrap());
+        }
+        res
+    }
+}
+
+pub fn charset_to_int(val: String, charset: String) -> u64 {
+    let mut res: u64 = 0;
+    for c in val.chars() {
+        res = res * charset.len() as u64 + charset.find(c).unwrap() as u64;
+    }
+    res
+}
+