Debug ssh key gen
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30
build.zig
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30
build.zig
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const std = @import("std");
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pub fn build(b: *std.Build) void {
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const target = b.standardTargetOptions(.{});
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const optimize = b.standardOptimizeOption(.{});
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const exe = b.addExecutable(.{
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.name = "crypto",
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.root_module = b.createModule(.{
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.root_source_file = b.path("src/main.zig"),
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.target = target,
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.optimize = optimize,
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}),
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});
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b.installArtifact(exe);
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const run_step = b.step("run", "Run the app");
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const run_cmd = b.addRunArtifact(exe);
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run_step.dependOn(&run_cmd.step);
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run_cmd.step.dependOn(b.getInstallStep());
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if (b.args) |args| {
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run_cmd.addArgs(args);
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}
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}
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82
build.zig.zon
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82
build.zig.zon
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.{
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// This is the default name used by packages depending on this one. For
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// example, when a user runs `zig fetch --save <url>`, this field is used
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// as the key in the `dependencies` table. Although the user can choose a
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// different name, most users will stick with this provided value.
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//
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// It is redundant to include "zig" in this name because it is already
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// within the Zig package namespace.
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.name = .crypto,
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// This is a [Semantic Version](https://semver.org/).
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// In a future version of Zig it will be used for package deduplication.
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.version = "0.0.0",
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// Together with name, this represents a globally unique package
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// identifier. This field is generated by the Zig toolchain when the
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// package is first created, and then *never changes*. This allows
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// unambiguous detection of one package being an updated version of
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// another.
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//
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// When forking a Zig project, this id should be regenerated (delete the
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// field and run `zig build`) if the upstream project is still maintained.
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// Otherwise, the fork is *hostile*, attempting to take control over the
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// original project's identity. Thus it is recommended to leave the comment
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// on the following line intact, so that it shows up in code reviews that
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// modify the field.
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.fingerprint = 0x6828288510fff01f,
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// Changing this has security and trust implications.
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// Tracks the earliest Zig version that the package considers to be a
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// supported use case.
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.minimum_zig_version = "0.15.2",
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// This field is optional.
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// Each dependency must either provide a `url` and `hash`, or a `path`.
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// `zig build --fetch` can be used to fetch all dependencies of a package, recursively.
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// Once all dependencies are fetched, `zig build` no longer requires
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// internet connectivity.
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.dependencies = .{
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// See `zig fetch --save <url>` for a command-line interface for adding dependencies.
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//.example = .{
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// // When updating this field to a new URL, be sure to delete the corresponding
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// // `hash`, otherwise you are communicating that you expect to find the old hash at
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// // the new URL. If the contents of a URL change this will result in a hash mismatch
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// // which will prevent zig from using it.
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// .url = "https://example.com/foo.tar.gz",
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//
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// // This is computed from the file contents of the directory of files that is
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// // obtained after fetching `url` and applying the inclusion rules given by
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// // `paths`.
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// //
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// // This field is the source of truth; packages do not come from a `url`; they
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// // come from a `hash`. `url` is just one of many possible mirrors for how to
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// // obtain a package matching this `hash`.
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// //
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// // Uses the [multihash](https://multiformats.io/multihash/) format.
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// .hash = "...",
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//
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// // When this is provided, the package is found in a directory relative to the
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// // build root. In this case the package's hash is irrelevant and therefore not
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// // computed. This field and `url` are mutually exclusive.
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// .path = "foo",
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//
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// // When this is set to `true`, a package is declared to be lazily
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// // fetched. This makes the dependency only get fetched if it is
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// // actually used.
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// .lazy = false,
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//},
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},
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// Specifies the set of files and directories that are included in this package.
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// Only files and directories listed here are included in the `hash` that
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// is computed for this package. Only files listed here will remain on disk
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// when using the zig package manager. As a rule of thumb, one should list
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// files required for compilation plus any license(s).
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// Paths are relative to the build root. Use the empty string (`""`) to refer to
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// the build root itself.
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// A directory listed here means that all files within, recursively, are included.
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.paths = .{
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"build.zig",
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"build.zig.zon",
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"src",
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// For example...
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//"LICENSE",
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//"README.md",
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},
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}
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197
src/main.zig
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197
src/main.zig
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@@ -0,0 +1,197 @@
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const std = @import("std");
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const p: u256 = (1 << 255) - 19;
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const Bx: u256 = 15112221349535807912866137220509078750507884956996801852099526895779190960831;
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const By: u256 = 46316835694926478169428394003475163141307993866256225615783033011972563869189;
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const d: u256 = 37095705934669439343138083508754565189542113879843219016388785533085940283555;
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const Point = struct {
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x: u256,
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y: u256,
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z: u256,
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t: u256,
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};
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const ident = Point{ .x = 0, .y = 1, .z = 1, .t = 0 };
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pub fn main() !void {
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var seed: [32]u8 = undefined;
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std.crypto.random.bytes(&seed);
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var hash = std.crypto.hash.sha2.Sha512.init(.{});
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hash.update(&seed);
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const digest = hash.finalResult();
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var scalar = digest[0..32].*;
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scalar[0] &= 0b11111100;
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scalar[31] &= 0b01111111;
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scalar[31] |= 0b01000000;
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const int_num: u256 = std.mem.readInt(u256, &scalar, .little);
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const B = Point{ .x = Bx, .y = By, .z = 1, .t = mul(Bx, By) };
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const product = scalar_mult(B, int_num);
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const final = compress(product);
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var gpa: std.heap.DebugAllocator(.{}) = .init;
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const alloc = gpa.allocator();
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defer {
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_ = gpa.deinit();
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}
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var args_it = try std.process.argsWithAllocator(alloc);
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defer args_it.deinit();
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_ = args_it.next();
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const user = args_it.next().?;
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const pub_pem = try encodePublicKey(alloc, final, user);
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const priv_pem = try encodePrivateKey(alloc, seed, final, user);
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defer alloc.free(pub_pem);
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defer alloc.free(priv_pem);
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std.debug.print("{s}", .{priv_pem});
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std.debug.print("{s}", .{pub_pem});
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}
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fn scalar_mult(pon: Point, scalar: u256) Point {
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var result = ident;
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var current = pon;
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var s = scalar;
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while (s > 0) : (s >>= 1) {
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if (s & 1 == 1) {
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result = add_points(result, current);
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}
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current = add_points(current, current);
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}
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return result;
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}
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fn add_points(p1: Point, p2: Point) Point {
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const a = mul(sub(p1.y, p1.x), sub(p2.y, p2.x));
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const b = mul(add(p1.y, p1.x), add(p2.y, p2.x));
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const c = mul(mul(mul(p1.t, 2), d), p2.t);
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const d_in = mul(mul(p1.z, 2), p2.z);
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const e = sub(b, a);
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const f = sub(d_in, c);
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const g = add(d_in, c);
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const h = add(b, a);
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const x3 = mul(e, f);
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const y3 = mul(g, h);
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const t3 = mul(e, h);
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const z3 = mul(f, g);
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return Point{ .x = x3, .y = y3, .t = t3, .z = z3 };
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}
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fn add(a: u256, b: u256) u256 {
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return (a + b) % p;
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}
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fn sub(a: u256, b: u256) u256 {
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return (a + p - b) % p;
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}
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fn mul(a: u256, b: u256) u256 {
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const wide = @as(u512, a) * @as(u512, b);
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return @intCast(wide % @as(u512, p));
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}
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fn modInv(a: u256) u256 {
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return modPow(a, p - 2);
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}
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fn modPow(base: u256, exp: u256) u256 {
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var result: u256 = 1;
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var b = base % p;
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var e = exp;
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while (e > 0) : (e >>= 1) {
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if (e & 1 == 1) result = mul(result, b);
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b = mul(b, b);
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}
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return result;
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}
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fn compress(point: Point) [32]u8 {
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const zinv = modInv(point.z);
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const x = mul(point.x, zinv);
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const y = mul(point.y, zinv);
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var bytes: [32]u8 = undefined;
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std.mem.writeInt(u256, &bytes, y, .little);
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bytes[31] |= @as(u8, @intCast(x & 1)) << 7;
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return bytes;
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}
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fn writeU32(buf: *std.Io.Writer, value: u32) !void {
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var bytes: [4]u8 = undefined;
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std.mem.writeInt(u32, &bytes, value, .big);
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_ = try buf.write(&bytes);
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}
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fn writeBytes(buf: *std.Io.Writer, data: []const u8) !void {
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try writeU32(buf, @intCast(data.len));
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_ = try buf.write(data);
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}
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pub fn encodePublicKey(
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allocator: std.mem.Allocator,
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public_key: [32]u8,
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comment: []const u8,
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) ![]u8 {
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var wire = std.Io.Writer.Allocating.init(allocator);
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defer wire.deinit();
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try writeBytes(&wire.writer, "ssh-ed25519");
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try writeBytes(&wire.writer, &public_key);
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const enc = std.base64.standard.Encoder;
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const b64_len = enc.calcSize(wire.writer.buffered().len);
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const b64_buf = try allocator.alloc(u8, b64_len);
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defer allocator.free(b64_buf);
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_ = enc.encode(b64_buf, wire.writer.buffered());
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return std.fmt.allocPrint(allocator, "ssh-ed25519 {s} {s}\n", .{ b64_buf, comment });
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}
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pub fn encodePrivateKey(
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allocator: std.mem.Allocator,
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seed: [32]u8,
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public_key: [32]u8,
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comment: []const u8,
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) ![]u8 {
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var pubkey_wire = std.Io.Writer.Allocating.init(allocator);
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defer pubkey_wire.deinit();
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try writeBytes(&pubkey_wire.writer, "ssh-ed25519");
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try writeBytes(&pubkey_wire.writer, &public_key);
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var private_blob: [64]u8 = undefined;
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@memcpy(private_blob[0..32], &seed);
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@memcpy(private_blob[32..64], &public_key);
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var check_bytes: [4]u8 = undefined;
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std.crypto.random.bytes(&check_bytes);
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const check = std.mem.readInt(u32, &check_bytes, .big);
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var priv = std.Io.Writer.Allocating.init(allocator);
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defer priv.deinit();
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try writeU32(&priv.writer, check);
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try writeU32(&priv.writer, check);
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try writeBytes(&priv.writer, "ssh-ed25519");
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try writeBytes(&priv.writer, &public_key);
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try writeBytes(&priv.writer, &private_blob);
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try writeBytes(&priv.writer, comment);
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var pad: u8 = 1;
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while (priv.writer.end % 8 != 0) : (pad += 1) {
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try priv.writer.writeByte(pad);
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}
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var outer = std.Io.Writer.Allocating.init(allocator);
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defer outer.deinit();
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_ = try outer.writer.write("openssh-key-v1\x00");
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try writeBytes(&outer.writer, "none");
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try writeBytes(&outer.writer, "none");
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try writeBytes(&outer.writer, "");
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try writeU32(&outer.writer, 1);
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try writeBytes(&outer.writer, pubkey_wire.writer.buffered());
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try writeBytes(&outer.writer, priv.writer.buffered());
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const enc = std.base64.standard.Encoder;
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const b64_len = enc.calcSize(outer.writer.buffered().len);
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const b64_buf = try allocator.alloc(u8, b64_len);
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defer allocator.free(b64_buf);
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_ = enc.encode(b64_buf, outer.writer.buffered());
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var result = std.Io.Writer.Allocating.init(allocator);
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_ = try result.writer.write("-----BEGIN OPENSSH PRIVATE KEY-----\n");
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var i: usize = 0;
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while (i < b64_buf.len) : (i += 70) {
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const end = @min(i + 70, b64_buf.len);
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_ = try result.writer.write(b64_buf[i..end]);
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_ = try result.writer.write("\n");
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}
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_ = try result.writer.write("-----END OPENSSH PRIVATE KEY-----\n");
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return result.toOwnedSlice();
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}
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