Starting to include RSA crypto.

src/rsa/public.rs

@@ -0,0 +1,30 @@
+use cryptonum::{BarrettUCN,UCN};
+use rsa::core::ACCEPTABLE_KEY_SIZES;
+
+#[derive(Clone,Debug,PartialEq,Eq)]
+pub struct RSAPublic {
+    pub(crate) byte_len: usize,
+    pub(crate) n: UCN,
+    pub(crate) nu: BarrettUCN,
+    pub(crate) e: UCN
+}
+
+impl RSAPublic {
+    /// Create a new RSA public key from the given components, which you found
+    /// via some other mechanism.
+    pub fn new(n: UCN, e: UCN) -> RSAPublic {
+        let len = n.bits();
+
+        for &(valid_bits, _) in ACCEPTABLE_KEY_SIZES.iter() {
+            if valid_bits > len {
+                return RSAPublic{
+                    byte_len: valid_bits / 8,
+                    n: n.clone(),
+                    nu: n.barrett_u(),
+                    e: e.clone()
+                };
+            }
+        }
+        panic!("Invalid RSA key size in new()")
+    }
+}