PRE reencryption to pubkey

nkms/crypto/pre/bbs98.py

@@ -1,3 +1,39 @@
-from npre.bbs98 import PRE  # noqa
+import base64
+import msgpack
+from nkms import crypto
+from npre.bbs98 import PRE as BasePRE
 
-# This is just to develop the interface, some more secure algos should be used
+
+def convert_priv(sk):
+    return b'0:' + base64.encodebytes(sk).strip()
+
+
+class PRE(BasePRE):
+    """
+    Public key based single-hop version of BBS98.
+    """
+    KEY_SIZE = 32
+
+    def priv2pub(self, priv):
+        """
+        Private key isa pure 32-bytes random number
+        """
+        if type(priv) is str:
+            priv = priv.encode()
+        if type(priv) is bytes:
+            priv = convert_priv(priv)
+        return super(PRE, self).priv2pub(priv)
+
+    def rekey(self, priv1, pub2):
+        priv_to = crypto.random(self.KEY_SIZE)
+        rk = self.rekey(convert_priv(priv1), convert_priv(priv_to), dtype=bytes)
+        epriv_to = self.encrypt(pub2, priv_to)
+        return msgpack.dumps([rk, epriv_to])
+
+    def reencrypt(self, rekey, emsg):
+        rk, epriv = msgpack.loads(rekey)
+        remsg = super(PRE, self).reencrypt(rk, emsg)
+        return msgpack.dumps([2, epriv, remsg])  # type 2 emsg
+
+    def decrypt(self, priv, emsg, padding=True):
+        pass

tests/test_default_crypto.py

@@ -1,5 +1,6 @@
 from nkms.crypto import default_algorithm
 from nkms.crypto import symmetric_from_algorithm
+from nkms.crypto import pre_from_algorithm
 from nkms import crypto
 
 
@@ -12,3 +13,7 @@ def test_symmetric():
     edata = cipher.encrypt(data)
     assert edata != data
     assert cipher.decrypt(edata) == data
+
+
+def test_pre():
+    pre = pre_from_algorithm(default_algorithm)