From 8371df4d8a0fa81fd79577e6085929449a568e84 Mon Sep 17 00:00:00 2001
From: Jay <wisehodl@pm.me>
Date: Fri, 24 Oct 2025 10:34:48 -0400
Subject: [PATCH] Converted sign module.

---
 src/sign.test.ts | 24 ++++++++++++++++++++++--
 src/sign.ts      | 36 ++++++++++++++++++++++++++++++++++++
 src/util.test.ts | 15 ++++++++++++++-
 3 files changed, 72 insertions(+), 3 deletions(-)

diff --git a/src/sign.test.ts b/src/sign.test.ts
index b0b0462..4e51209 100644
--- a/src/sign.test.ts
+++ b/src/sign.test.ts
@@ -1,2 +1,22 @@
-import { test } from "vitest";
-test("placeholder", () => {});
+import { describe, test, expect } from "vitest";
+import { Sign } from "./sign";
+import { testSK, testEvent } from "./util.test";
+
+describe("Sign.sign", () => {
+  test("produces correct signature", () => {
+    const signature = Sign.sign(testEvent.id, testSK);
+    expect(signature).toBe(testEvent.sig);
+  });
+
+  test("throws on invalid event ID", () => {
+    expect(() => Sign.sign("thisisabadeventid", testSK)).toThrow(
+      "event id must be 64 hex characters",
+    );
+  });
+
+  test("throws on invalid private key", () => {
+    expect(() => Sign.sign(testEvent.id, "thisisabadsecretkey")).toThrow(
+      "private key must be 64 lowercase hex characters",
+    );
+  });
+});
diff --git a/src/sign.ts b/src/sign.ts
index e69de29..ece5344 100644
--- a/src/sign.ts
+++ b/src/sign.ts
@@ -0,0 +1,36 @@
+import * as secp from "@noble/secp256k1";
+import { schnorr } from "@noble/secp256k1";
+import { hmac } from "@noble/hashes/hmac.js";
+import { sha256 } from "@noble/hashes/sha2.js";
+import { MalformedIDError, MalformedPrivKeyError } from "./errors";
+
+secp.hashes.hmacSha256 = (key, msg) => hmac(sha256, key, msg);
+secp.hashes.sha256 = sha256;
+
+/**
+ * Generates a Schnorr signature for the given event ID using the provided private key.
+ * @param eventID - 64-character lowercase hexadecimal event ID
+ * @param privateKey - 64-character lowercase hexadecimal private key
+ * @returns 128-character lowercase hexadecimal signature
+ * @throws {MalformedIDError} If event ID is not 64 hex characters
+ * @throws {MalformedPrivKeyError} If private key is not 64 lowercase hex characters
+ */
+function sign(eventID: string, privateKey: string): string {
+  const privateKeyBytes = Buffer.from(privateKey, "hex");
+  if (privateKeyBytes.length !== 32) {
+    throw new MalformedPrivKeyError();
+  }
+
+  const idBytes = Buffer.from(eventID, "hex");
+  if (idBytes.length !== 32) {
+    throw new MalformedIDError();
+  }
+
+  const auxRand = sha256(privateKeyBytes);
+  const signature = schnorr.sign(idBytes, privateKeyBytes, auxRand);
+  return Buffer.from(signature).toString("hex");
+}
+
+export const Sign = {
+  sign,
+};
diff --git a/src/util.test.ts b/src/util.test.ts
index 2cc7a3a..2677400 100644
--- a/src/util.test.ts
+++ b/src/util.test.ts
@@ -1,8 +1,21 @@
 import { test } from "vitest";
+import type { Event } from "./types";
+
+test("placeholder", () => {});
 
 export const testSK =
   "f43a0435f69529f310bbd1d6263d2fbf0977f54bfe2310cc37ae5904b83bb167";
 export const testPK =
   "cfa87f35acbde29ba1ab3ee42de527b2cad33ac487e80cf2d6405ea0042c8fef";
 
-test("placeholder", () => {});
+export const testEvent: Event = {
+  id: "c7a702e6158744ca03508bbb4c90f9dbb0d6e88fefbfaa511d5ab24b4e3c48ad",
+  pubkey: testPK,
+  created_at: 1760740551,
+  kind: 1,
+  tags: [],
+  content: "hello world",
+  sig: "0fb7c1eaa867c4d16000587f2fb26c0b67e7e069f35d1acbb2d385a7813eb342418714a4c4fd4c04b9d7e2477e7a2208102ef536df09b79b84b8f3c41e8e5708",
+};
+
+export const testEventJSON = `{"id":"c7a702e6158744ca03508bbb4c90f9dbb0d6e88fefbfaa511d5ab24b4e3c48ad","pubkey":"cfa87f35acbde29ba1ab3ee42de527b2cad33ac487e80cf2d6405ea0042c8fef","created_at":1760740551,"kind":1,"tags":[],"content":"hello world","sig":"0fb7c1eaa867c4d16000587f2fb26c0b67e7e069f35d1acbb2d385a7813eb342418714a4c4fd4c04b9d7e2477e7a2208102ef536df09b79b84b8f3c41e8e5708"}`;