pubkey.c, ...: Support Bernstein's `X25519' key-agreement algorithm.

[catacomb-python] / catacomb / __init__.py

diff --git a/catacomb/__init__.py b/catacomb/__init__.py
index 9963572765f8882d7e11ffc8736dbea8374599be..115e8fe785cec67af3ce5d46b0480ad4866cea08 100644 (file)
--- a/catacomb/__init__.py
+++ b/catacomb/__init__.py
@@ -458,6 +458,43 @@ class _tmp:
   def sign(me, msg, enc): return me.privop(enc.encode(msg, me.n.nbits))
 _augment(RSAPriv, _tmp)
 
+###--------------------------------------------------------------------------
+### Bernstein's elliptic curve crypto.
+
+X25519_BASE = \
+  bytes('0900000000000000000000000000000000000000000000000000000000000000')
+
+Z128 = bytes('00000000000000000000000000000000')
+
+class _BoxyPub (object):
+  def __init__(me, pub, *kw, **kwargs):
+    if len(pub) != me._PUBSZ: raise ValueError, 'bad public key'
+    super(_BoxyPub, me).__init__(*kw, **kwargs)
+    me.pub = pub
+
+class _BoxyPriv (_BoxyPub):
+  def __init__(me, priv, pub = None, *kw, **kwargs):
+    if len(priv) != me._KEYSZ: raise ValueError, 'bad private key'
+    if pub is None: pub = me._op(priv, me._BASE)
+    super(_BoxyPriv, me).__init__(pub = pub, *kw, **kwargs)
+    me.priv = priv
+  def agree(me, you): return me._op(me.priv, you.pub)
+  def boxkey(me, recip):
+    return me._hashkey(me.agree(recip))
+  def box(me, recip, n, m):
+    return secret_box(me.boxkey(recip), n, m)
+  def unbox(me, recip, n, c):
+    return secret_unbox(me.boxkey(recip, n, c))
+
+class X25519Pub (_BoxyPub):
+  _PUBSZ = X25519_PUBSZ
+  _BASE = X25519_BASE
+
+class X25519Priv (_BoxyPriv, X25519Pub):
+  _KEYSZ = X25519_KEYSZ
+  def _op(me, k, X): return x25519(k, X)
+  def _hashkey(me, z): return hsalsa20_prf(z, Z128)
+
 ###--------------------------------------------------------------------------
 ### Built-in named curves and prime groups.