it's a flake now

.direnv/bin/nix-direnv-reload

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+set -e
+if [[ ! -d "/Users/clark/Aims/rust/diffie-hellman" ]]; then
+  echo "Cannot find source directory; Did you move it?"
+  echo "(Looking for "/Users/clark/Aims/rust/diffie-hellman")"
+  echo 'Cannot force reload with this script - use "direnv reload" manually and then try again'
+  exit 1
+fi
+
+# rebuild the cache forcefully
+_nix_direnv_force_reload=1 direnv exec "/Users/clark/Aims/rust/diffie-hellman" true
+
+# Update the mtime for .envrc.
+# This will cause direnv to reload again - but without re-building.
+touch "/Users/clark/Aims/rust/diffie-hellman/.envrc"
+
+# Also update the timestamp of whatever profile_rc we have.
+# This makes sure that we know we are up to date.
+touch -r "/Users/clark/Aims/rust/diffie-hellman/.envrc" "/Users/clark/Aims/rust/diffie-hellman/.direnv"/*.rc

Cargo.toml

@@ -2,6 +2,8 @@
 name = "diffie-hellman"
 version = "0.1.0"
 edition = "2024"
+description = "toy implementation of diffie-hellman key exchange"
+homepage = "https://g.pyrope.net/diffie-hellman"
 
 [dependencies]
 ntt = "0.1.9"

default.nix

@@ -0,0 +1,55 @@
+{ lib
+, naersk
+, stdenv
+, clangStdenv
+, hostPlatform
+, targetPlatform
+, pkg-config
+, libiconv
+, rustfmt
+, cargo
+, rustc
+  # , llvmPackages # Optional
+  # , protobuf     # Optional
+}:
+
+let
+  cargoToml = (builtins.fromTOML (builtins.readFile ./Cargo.toml));
+in
+
+naersk.lib."${targetPlatform.system}".buildPackage rec {
+  src = ./.;
+
+  buildInputs = [
+    rustfmt
+    pkg-config
+    cargo
+    rustc
+    libiconv
+  ];
+  checkInputs = [ cargo rustc ];
+
+  doCheck = true;
+  CARGO_BUILD_INCREMENTAL = "false";
+  RUST_BACKTRACE = "full";
+  copyLibs = true;
+
+  # Optional things you might need:
+  #
+  # If you depend on `libclang`:
+  # LIBCLANG_PATH = "${llvmPackages.libclang}/lib";
+  #
+  # If you depend on protobuf:
+  # PROTOC = "${protobuf}/bin/protoc";
+  # PROTOC_INCLUDE = "${protobuf}/include";
+
+  name = cargoToml.package.name;
+  version = cargoToml.package.version;
+
+  meta = with lib; {
+    description = cargoToml.package.description;
+    homepage = cargoToml.package.homepage;
+    license = with licenses; [ mit ];
+    maintainers = with maintainers; [ ];
+  };
+}

flake.lock

@@ -0,0 +1,88 @@
+{
+  "nodes": {
+    "fenix": {
+      "inputs": {
+        "nixpkgs": [
+          "naersk",
+          "nixpkgs"
+        ],
+        "rust-analyzer-src": "rust-analyzer-src"
+      },
+      "locked": {
+        "lastModified": 1752475459,
+        "narHash": "sha256-z6QEu4ZFuHiqdOPbYss4/Q8B0BFhacR8ts6jO/F/aOU=",
+        "owner": "nix-community",
+        "repo": "fenix",
+        "rev": "bf0d6f70f4c9a9cf8845f992105652173f4b617f",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "fenix",
+        "type": "github"
+      }
+    },
+    "naersk": {
+      "inputs": {
+        "fenix": "fenix",
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1776200608,
+        "narHash": "sha256-broZ6RFQr4Fv0wT73gGmzNX14A43TmTFF8g4wDKlNss=",
+        "owner": "nmattia",
+        "repo": "naersk",
+        "rev": "8b23250ab45c2a38cd91031aee26478ca4d0a28e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nmattia",
+        "repo": "naersk",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1776329215,
+        "narHash": "sha256-a8BYi3mzoJ/AcJP8UldOx8emoPRLeWqALZWu4ZvjPXw=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "b86751bc4085f48661017fa226dee99fab6c651b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "naersk": "naersk",
+        "nixpkgs": "nixpkgs"
+      }
+    },
+    "rust-analyzer-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1752428706,
+        "narHash": "sha256-EJcdxw3aXfP8Ex1Nm3s0awyH9egQvB2Gu+QEnJn2Sfg=",
+        "owner": "rust-lang",
+        "repo": "rust-analyzer",
+        "rev": "591e3b7624be97e4443ea7b5542c191311aa141d",
+        "type": "github"
+      },
+      "original": {
+        "owner": "rust-lang",
+        "ref": "nightly",
+        "repo": "rust-analyzer",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,79 @@
+# https://hoverbear.org/blog/a-flake-for-your-crate/
+{
+  description = "Diffie hellman";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    naersk.url = "github:nmattia/naersk";
+    naersk.inputs.nixpkgs.follows = "nixpkgs";
+  };
+
+  outputs = { self, nixpkgs, naersk }:
+    let
+      cargoToml = (builtins.fromTOML (builtins.readFile ./Cargo.toml));
+      supportedSystems = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];
+      forAllSystems = f: nixpkgs.lib.genAttrs supportedSystems (system: f system);
+    in
+    {
+      overlay = final: prev: {
+        "${cargoToml.package.name}" = final.callPackage ./. { inherit naersk; };
+      };
+
+      packages = forAllSystems (system:
+        let
+          pkgs = import nixpkgs {
+            inherit system;
+            overlays = [
+              self.overlay
+            ];
+          };
+        in
+        {
+          "${cargoToml.package.name}" = pkgs."${cargoToml.package.name}";
+        });
+
+
+      defaultPackage = forAllSystems (system: (import nixpkgs {
+        inherit system;
+        overlays = [ self.overlay ];
+      })."${cargoToml.package.name}");
+
+      checks = forAllSystems (system:
+        let
+          pkgs = import nixpkgs {
+            inherit system;
+            overlays = [
+              self.overlay
+            ];
+          };
+        in
+        {
+          format = pkgs.runCommand "check-format"
+            {
+              buildInputs = with pkgs; [ rustfmt cargo ];
+            } ''
+            ${pkgs.rustfmt}/bin/cargo-fmt fmt --manifest-path ${./.}/Cargo.toml -- --check
+            ${pkgs.nixpkgs-fmt}/bin/nixpkgs-fmt --check ${./.}
+            touch $out # it worked!
+          '';
+          "${cargoToml.package.name}" = pkgs."${cargoToml.package.name}";
+        });
+      devShells = forAllSystems (system:
+        let
+          pkgs = import nixpkgs {
+            inherit system;
+            overlays = [ self.overlay ];
+          };
+        in
+        pkgs.mkShell {
+          inputsFrom = with pkgs; [
+            pkgs."${cargoToml.package.name}"
+          ];
+          buildInputs = with pkgs; [
+            rustfmt
+            nixpkgs-fmt
+          ];
+          LIBCLANG_PATH = "${pkgs.llvmPackages.libclang.lib}/lib";
+        });
+    };
+}

src/main.rs

@@ -11,7 +11,7 @@ fn main() {
         let a = rpassword::prompt_password("a = ").unwrap();
         let a = a.parse::<u32>().unwrap();
 
-        println!("{}", mod_exp(i64::from(g), i64::from(a), i64::from(p)));
+        println!("gª mod p = {}", mod_exp(i64::from(g), i64::from(a), i64::from(p)));
     } else {
         let rng = rand::rng();