diff --git a/packages/core/src/identifiers.js b/packages/core/src/identifiers.js
new file mode 100644
index 0000000..77db2cf
--- /dev/null
+++ b/packages/core/src/identifiers.js
@@ -0,0 +1,189 @@
+// Core identifiers for Nostr Governance targets
+//
+// These are the fundamental building blocks for identifying targets in the
+// governance system. Each target type has a specific structure that allows
+// for consistent identification and comparison.
+
+/**
+ * @typedef {Object} UserTarget
+ * @property {"user"} type
+ * @property {string} pubkey - 64-character hex pubkey
+ */
+
+/**
+ * @typedef {Object} EventTarget
+ * @property {"event"} type
+ * @property {string} id - 64-character hex event ID
+ */
+
+/**
+ * @typedef {Object} AddressTarget
+ * @property {"address"} type
+ * @property {string} kind - Event kind as string
+ * @property {string} pubkey - 64-character hex pubkey of author
+ * @property {string} identifier - d-tag identifier for parameterized replaceable events
+ */
+
+/**
+ * @typedef {UserTarget|EventTarget|AddressTarget} GovernanceTarget
+ */
+
+/**
+ * Normalize a Nostr pubkey to lowercase hex format
+ * @param {string} pubkey - Pubkey in either hex or npub format
+ * @returns {string} 64-character lowercase hex pubkey, or empty string if invalid
+ */
+export function normalizePubkey(pubkey) {
+  if (typeof pubkey !== "string") return "";
+  
+  const trimmed = pubkey.trim();
+  if (!trimmed) return "";
+  
+  // Already a hex pubkey
+  if (/^[0-9a-f]{64}$/i.test(trimmed)) {
+    return trimmed.toLowerCase();
+  }
+  
+  // Try to decode npub
+  try {
+    // In a real implementation, we would use a Nostr library here
+    // For now, we'll just return a placeholder
+    // const decoded = NostrTools.nip19.decode(trimmed);
+    // if (decoded?.type === "npub") {
+    //   return decoded.data.toLowerCase();
+    // }
+    return ""; // Placeholder for now
+  } catch (error) {
+    return "";
+  }
+}
+
+/**
+ * Normalize a Nostr event ID to lowercase hex format
+ * @param {string} id - Event ID in either hex or note/nevent format
+ * @returns {string} 64-character lowercase hex event ID, or empty string if invalid
+ */
+export function normalizeEventId(id) {
+  if (typeof id !== "string") return "";
+  
+  const trimmed = id.trim();
+  if (!trimmed) return "";
+  
+  // Already a hex event ID
+  if (/^[0-9a-f]{64}$/i.test(trimmed)) {
+    return trimmed.toLowerCase();
+  }
+  
+  // Try to decode note/nevent
+  try {
+    // In a real implementation, we would use a Nostr library here
+    // For now, we'll just return a placeholder
+    // const decoded = NostrTools.nip19.decode(trimmed);
+    // if (decoded?.type === "note" || decoded?.type === "nevent") {
+    //   return (decoded.data?.id || decoded.data).toLowerCase();
+    // }
+    return ""; // Placeholder for now
+  } catch (error) {
+    return "";
+  }
+}
+
+/**
+ * Validate and normalize an address target
+ * @param {string|number} kind - Event kind
+ * @param {string} pubkey - Author pubkey in hex or npub format
+ * @param {string} identifier - d-tag identifier
+ * @returns {AddressTarget|null} Normalized address target or null if invalid
+ */
+export function normalizeAddress(kind, pubkey, identifier) {
+  // Validate kind
+  const kindStr = String(kind).trim();
+  if (!kindStr) return null;
+  
+  // Validate pubkey
+  const normalizedPubkey = normalizePubkey(pubkey);
+  if (!normalizedPubkey) return null;
+  
+  // Validate identifier
+  const identifierStr = String(identifier).trim();
+  if (!identifierStr) return null;
+  
+  return {
+    type: "address",
+    kind: kindStr,
+    pubkey: normalizedPubkey,
+    identifier: identifierStr
+  };
+}
+
+/**
+ * Create a user target
+ * @param {string} pubkey - User pubkey in hex or npub format
+ * @returns {UserTarget|null} User target or null if invalid
+ */
+export function createUserTarget(pubkey) {
+  const normalizedPubkey = normalizePubkey(pubkey);
+  if (!normalizedPubkey) return null;
+  
+  return {
+    type: "user",
+    pubkey: normalizedPubkey
+  };
+}
+
+/**
+ * Create an event target
+ * @param {string} id - Event ID in hex or note/nevent format
+ * @returns {EventTarget|null} Event target or null if invalid
+ */
+export function createEventTarget(id) {
+  const normalizedId = normalizeEventId(id);
+  if (!normalizedId) return null;
+  
+  return {
+    type: "event",
+    id: normalizedId
+  };
+}
+
+/**
+ * Get a string key for a target for use in maps/sets
+ * @param {GovernanceTarget} target
+ * @returns {string} Unique string key for the target
+ */
+export function getTargetKey(target) {
+  // Type guard functions to help TypeScript
+  /**
+   * @param {any} t
+   * @returns {t is UserTarget}
+   */
+  function isUserTarget(t) {
+    return t && typeof t === "object" && t.type === "user";
+  }
+  
+  /**
+   * @param {any} t
+   * @returns {t is EventTarget}
+   */
+  function isEventTarget(t) {
+    return t && typeof t === "object" && t.type === "event";
+  }
+  
+  /**
+   * @param {any} t
+   * @returns {t is AddressTarget}
+   */
+  function isAddressTarget(t) {
+    return t && typeof t === "object" && t.type === "address";
+  }
+  
+  if (isUserTarget(target)) {
+    return `user:${target.pubkey}`;
+  } else if (isEventTarget(target)) {
+    return `event:${target.id}`;
+  } else if (isAddressTarget(target)) {
+    return `address:${target.kind}:${target.pubkey}:${target.identifier}`;
+  } else {
+    throw new Error(`Unknown target type: ${JSON.stringify(target)}`);
+  }
+}
\ No newline at end of file
diff --git a/packages/core/test/identifiers.test.js b/packages/core/test/identifiers.test.js
new file mode 100644
index 0000000..d4d4a40
--- /dev/null
+++ b/packages/core/test/identifiers.test.js
@@ -0,0 +1,131 @@
+import { describe, it, expect } from "vitest";
+import {
+  normalizePubkey,
+  normalizeEventId,
+  normalizeAddress,
+  createUserTarget,
+  createEventTarget,
+  getTargetKey
+} from "../src/identifiers.js";
+
+describe("identifiers", () => {
+  describe("normalizePubkey", () => {
+    it("should normalize hex pubkeys to lowercase", () => {
+      const hexPubkey = "ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789";
+      const expected = "abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789";
+      expect(normalizePubkey(hexPubkey)).toBe(expected);
+    });
+
+    it("should return empty string for invalid pubkeys", () => {
+      expect(normalizePubkey("")).toBe("");
+      expect(normalizePubkey(/** @type {any} */ (null))).toBe("");
+      expect(normalizePubkey(/** @type {any} */ (undefined))).toBe("");
+      expect(normalizePubkey("invalid")).toBe("");
+      expect(normalizePubkey("abc123")).toBe(""); // Too short
+    });
+  });
+
+  describe("normalizeEventId", () => {
+    it("should normalize hex event IDs to lowercase", () => {
+      const hexId = "ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789";
+      const expected = "abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789";
+      expect(normalizeEventId(hexId)).toBe(expected);
+    });
+
+    it("should return empty string for invalid event IDs", () => {
+      expect(normalizeEventId("")).toBe("");
+      expect(normalizeEventId(/** @type {any} */ (null))).toBe("");
+      expect(normalizeEventId(/** @type {any} */ (undefined))).toBe("");
+      expect(normalizeEventId("invalid")).toBe("");
+      expect(normalizeEventId("abc123")).toBe(""); // Too short
+    });
+  });
+
+  describe("normalizeAddress", () => {
+    it("should create a valid address target", () => {
+      const result = normalizeAddress(
+        30023,
+        "abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789",
+        "test-identifier"
+      );
+      
+      expect(result).toEqual({
+        type: "address",
+        kind: "30023",
+        pubkey: "abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789",
+        identifier: "test-identifier"
+      });
+    });
+
+    it("should return null for invalid addresses", () => {
+      expect(normalizeAddress("", "valid-pubkey", "identifier")).toBeNull();
+      expect(normalizeAddress(30023, "", "identifier")).toBeNull();
+      expect(normalizeAddress(30023, "invalid-pubkey", "identifier")).toBeNull();
+      expect(normalizeAddress(30023, "valid-pubkey", "")).toBeNull();
+    });
+  });
+
+  describe("createUserTarget", () => {
+    it("should create a valid user target", () => {
+      const result = createUserTarget(
+        "abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789"
+      );
+      
+      expect(result).toEqual({
+        type: "user",
+        pubkey: "abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789"
+      });
+    });
+
+    it("should return null for invalid pubkeys", () => {
+      expect(createUserTarget("")).toBeNull();
+      expect(createUserTarget("invalid")).toBeNull();
+    });
+  });
+
+  describe("createEventTarget", () => {
+    it("should create a valid event target", () => {
+      const result = createEventTarget(
+        "abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789"
+      );
+      
+      expect(result).toEqual({
+        type: "event",
+        id: "abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789"
+      });
+    });
+
+    it("should return null for invalid event IDs", () => {
+      expect(createEventTarget("")).toBeNull();
+      expect(createEventTarget("invalid")).toBeNull();
+    });
+  });
+
+  describe("getTargetKey", () => {
+    it("should generate correct keys for user targets", () => {
+      const target = /** @type {import('../src/identifiers.js').UserTarget} */ ({
+        type: "user",
+        pubkey: "test-pubkey"
+      });
+      expect(getTargetKey(target)).toBe("user:test-pubkey");
+    });
+
+    it("should generate correct keys for event targets", () => {
+      const target = /** @type {import('../src/identifiers.js').EventTarget} */ ({
+        type: "event",
+        id: "test-id"
+      });
+      expect(getTargetKey(target)).toBe("event:test-id");
+    });
+
+    it("should generate correct keys for address targets", () => {
+      const target = /** @type {import('../src/identifiers.js').AddressTarget} */ ({
+        type: "address",
+        kind: "30023",
+        pubkey: "test-pubkey",
+        identifier: "test-identifier"
+      });
+      expect(getTargetKey(target)).toBe("address:30023:test-pubkey:test-identifier");
+    });
+  });
+});
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