fix random number generation + asymmetric key generation

src/utils.rs

@@ -0,0 +1,20 @@
+use rand::rngs::StdRng;
+use rand::Rng;
+use rand::SeedableRng;
+use rug::Integer;
+
+pub fn generate_random_odd_integer(num_bits: u32) -> Integer {
+    std::iter::repeat_with(|| generate_random_integer(num_bits))
+        .find(|p: &Integer| p.is_odd())
+        .unwrap()
+}
+
+pub fn generate_random_integer(num_bits: u32) -> Integer {
+    let mut rng = StdRng::from_os_rng();
+    let mut x = Integer::from(1);
+    for _ in 1..num_bits {
+        x <<= 1;
+        x += rng.random_range(0..=1);
+    }
+    x
+}