diff --git a/src/nostr/client.py b/src/nostr/client.py
index 68a5059..17d2715 100644
--- a/src/nostr/client.py
+++ b/src/nostr/client.py
@@ -11,9 +11,15 @@ import concurrent.futures
 from typing import List, Optional, Callable
 from pathlib import Path
 
-from monstr.client.client import ClientPool
-from monstr.encrypt import Keys, NIP4Encrypt
-from monstr.event.event import Event
+try:
+    from monstr.client.client import ClientPool
+    from monstr.encrypt import Keys, NIP4Encrypt
+    from monstr.event.event import Event
+except ImportError:  # Fallback placeholders when monstr is unavailable
+    ClientPool = None
+    NIP4Encrypt = None
+    Event = None
+    from .coincurve_keys import Keys
 
 import threading
 import uuid
@@ -102,6 +108,8 @@ class NostrClient:
         """
         try:
             logger.debug("Initializing ClientPool with relays.")
+            if ClientPool is None:
+                raise ImportError("monstr library is required for ClientPool")
             self.client_pool = ClientPool(self.relays)
 
             # Start the ClientPool in a separate thread
@@ -256,6 +264,8 @@ class NostrClient:
                 content_base64 = event.content
 
                 if event.kind == Event.KIND_ENCRYPT:
+                    if NIP4Encrypt is None:
+                        raise ImportError("monstr library required for NIP4 encryption")
                     nip4_encrypt = NIP4Encrypt(self.key_manager.keys)
                     content_base64 = nip4_encrypt.decrypt_message(
                         event.content, event.pub_key
@@ -500,6 +510,8 @@ class NostrClient:
             event.created_at = int(time.time())
 
             if to_pubkey:
+                if NIP4Encrypt is None:
+                    raise ImportError("monstr library required for NIP4 encryption")
                 nip4_encrypt = NIP4Encrypt(self.key_manager.keys)
                 event.content = nip4_encrypt.encrypt_message(event.content, to_pubkey)
                 event.kind = Event.KIND_ENCRYPT
diff --git a/src/nostr/coincurve_keys.py b/src/nostr/coincurve_keys.py
new file mode 100644
index 0000000..99604ac
--- /dev/null
+++ b/src/nostr/coincurve_keys.py
@@ -0,0 +1,45 @@
+from __future__ import annotations
+
+from bech32 import bech32_encode, bech32_decode, convertbits
+from coincurve import PrivateKey, PublicKey
+
+
+class Keys:
+    """Minimal replacement for monstr.encrypt.Keys using coincurve."""
+
+    def __init__(self, priv_k: str | None = None, pub_k: str | None = None):
+        if priv_k is not None:
+            if priv_k.startswith("nsec"):
+                priv_k = self.bech32_to_hex(priv_k)
+            self._priv_k = priv_k
+            priv = PrivateKey(bytes.fromhex(priv_k))
+        else:
+            priv = PrivateKey()
+            self._priv_k = priv.to_hex()
+
+        pub = priv.public_key.format(compressed=True).hex()[2:]
+        if pub_k:
+            if pub_k.startswith("npub"):
+                pub_k = self.bech32_to_hex(pub_k)
+            self._pub_k = pub_k
+        else:
+            self._pub_k = pub
+
+    @staticmethod
+    def hex_to_bech32(key_str: str, prefix: str = "npub") -> str:
+        data = convertbits(bytes.fromhex(key_str), 8, 5)
+        return bech32_encode(prefix, data)
+
+    @staticmethod
+    def bech32_to_hex(key: str) -> str:
+        hrp, data = bech32_decode(key)
+        if data is None:
+            raise ValueError("Invalid bech32 key")
+        decoded = convertbits(data, 5, 8, False)
+        return bytes(decoded).hex()
+
+    def private_key_hex(self) -> str:
+        return self._priv_k
+
+    def public_key_hex(self) -> str:
+        return self._pub_k
diff --git a/src/nostr/key_manager.py b/src/nostr/key_manager.py
index 2aab346..71f8973 100644
--- a/src/nostr/key_manager.py
+++ b/src/nostr/key_manager.py
@@ -7,7 +7,7 @@ from bech32 import bech32_encode, convertbits
 
 from local_bip85.bip85 import BIP85
 from bip_utils import Bip39SeedGenerator
-from monstr.encrypt import Keys
+from .coincurve_keys import Keys
 
 logger = logging.getLogger(__name__)
 
diff --git a/src/requirements.txt b/src/requirements.txt
index 690ee04..647ce21 100644
--- a/src/requirements.txt
+++ b/src/requirements.txt
@@ -3,7 +3,7 @@ termcolor>=1.1.0
 cryptography>=40.0.2
 bip-utils>=2.5.0
 bech32==1.2.0
-monstr @ git+https://github.com/monty888/monstr.git@master#egg=monstr
+coincurve>=18.0.0
 mnemonic
 aiohttp
 bcrypt