Allow instantiation of PublicKey from bech32/npub format

nostr/key.py

@@ -10,6 +10,13 @@ class PublicKey:
     def __init__(self, raw_bytes: bytes) -> None:
         self.raw_bytes = raw_bytes
 
+    @classmethod
+    def from_npub(cls, npub: str):
+        """Load a PublicKey from its bech32/npub form"""
+        hrp, data, spec = bech32.bech32_decode(npub)
+        raw_public = bech32.convertbits(data, 5, 8)[:-1]
+        return cls(bytes(raw_public))
+
     def bech32(self) -> str:
         converted_bits = bech32.convertbits(self.raw_bytes, 8, 5)
         return bech32.bech32_encode("npub", converted_bits, bech32.Encoding.BECH32)
@@ -85,7 +92,7 @@ def sign_message_hash(self, hash: bytes) -> str:
         sk = secp256k1.PrivateKey(self.raw_secret)
         sig = sk.schnorr_sign(hash, None, raw=True)
         return sig.hex()
-    
+
     def __eq__(self, other):
         return self.raw_secret == other.raw_secret
 
@@ -94,4 +101,4 @@ def __eq__(self, other):
 @ffi.callback("int (unsigned char *, const unsigned char *, const unsigned char *, void *)")
 def copy_x(output, x32, y32, data):
     ffi.memmove(output, x32, 32)
-    return 1
+    return 1

test/test_key.py

@@ -1,4 +1,4 @@
-from nostr.key import PrivateKey
+from nostr.key import PrivateKey, PublicKey
 
 
 def test_eq_true():
@@ -21,3 +21,9 @@ def test_from_nsec():
     pk1 = PrivateKey()
     pk2 = PrivateKey.from_nsec(pk1.bech32())
     assert pk1.raw_secret == pk2.raw_secret
+
+def test_from_npub():
+    """ PublicKey.from_npub should yield the source's raw_bytes """
+    pk1 = PrivateKey()
+    pk2 = PublicKey.from_npub(pk1.public_key.bech32())
+    assert pk1.public_key.raw_bytes == pk2.raw_bytes