Prime finite base field with test cases, add, sub, and partial mul (#9)

* feat: optimized modular addition

* feat: implement optimized sub

* test: addition and subtraction

* chore: docs

* tests: red green tests for adding mul, div, neg, inv

* docs: add explainer on purpose of finite field

* feat: additive inverse

* feat: montgomery multiplication

* fix: favor const implementations

* fix: constant time montgomery multiply

* fix: clean up comment

Cargo.toml

@@ -14,7 +14,10 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+hex-literal = "0.4.1"
+num-traits = "0.2.19"
+subtle = "2.6.1"
 
 [lib]
 
-[dev-dependencies]
+[dev-dependencies]