Give credit where credit is due.

src/cryptonum/multiplication.rs

@@ -3,28 +3,29 @@ use cryptonum::{U192,   U256,   U384,   U512,   U576,
                 U15360};
 use std::ops::{Mul,MulAssign};
 
-fn raw_multiplication(x: &[u64], y: &[u64], z: &mut [u64])
+// This is algorithm 14.12 from "Handbook of Applied Cryptography"
+fn raw_multiplication(x: &[u64], y: &[u64], w: &mut [u64])
 {
     assert_eq!(x.len(), y.len());
-    assert_eq!(x.len() * 2, z.len());
+    assert_eq!(x.len() * 2, w.len());
 
     // clear out the destination array, because we're going to use it as a
     // temporary
-    for i in 0..z.len() {
-        z[i] = 0;
+    for i in 0..w.len() {
+        w[i] = 0;
     }
 
     for i in 0..y.len() { // this may legitimately be off by one
         let mut carry = 0;
         for j in 0..x.len() { // ditto
-            let old = z[i+j] as u128;
+            let old = w[i+j] as u128;
             let x128 = x[j] as u128;
             let y128 = y[i] as u128;
             let uv = old + (x128 * y128) + carry;
-            z[i+j] = uv as u64;
+            w[i+j] = uv as u64;
             carry = uv >> 64;
         }
-        z[i+x.len()] = carry as u64;
+        w[i+x.len()] = carry as u64;
     }
 }