From 12e678a9ce547c77f4a0efaa184e13f17da41cdc Mon Sep 17 00:00:00 2001
From: Berry Schoenmakers <l.a.m.schoenmakers@tue.nl>
Date: Sun, 25 Feb 2024 12:53:59 +0100
Subject: [PATCH] PRSS details from asyncoro to runtime.

---
 mpyc/__init__.py |  2 +-
 mpyc/asyncoro.py | 24 +++++-------------------
 mpyc/mpctools.py |  7 ++++---
 mpyc/runtime.py  | 25 +++++++++++++++++++++++++
 4 files changed, 35 insertions(+), 23 deletions(-)

diff --git a/mpyc/__init__.py b/mpyc/__init__.py
index f8f421c..06ce6c1 100644
--- a/mpyc/__init__.py
+++ b/mpyc/__init__.py
@@ -29,7 +29,7 @@
 and statistics (securely mimicking Python’s statistics module).
 """
 
-__version__ = '0.9.8'
+__version__ = '0.9.9'
 __license__ = 'MIT License'
 
 import os
diff --git a/mpyc/asyncoro.py b/mpyc/asyncoro.py
index 9bfee6e..59b0f56 100644
--- a/mpyc/asyncoro.py
+++ b/mpyc/asyncoro.py
@@ -5,7 +5,6 @@
 import sys
 import traceback
 from struct import pack, unpack_from
-import itertools
 import functools
 import typing
 from asyncio import Protocol, Future, Task
@@ -54,11 +53,7 @@ def connection_made(self, transport):
             rt = self.runtime
             pid_keys = [rt.pid.to_bytes(2, 'little')]  # send pid
             if not rt.options.no_prss:
-                m = len(rt.parties)
-                t = rt.threshold
-                for subset in itertools.combinations(range(m), m - t):
-                    if subset[0] == rt.pid and self.peer_pid in subset:
-                        pid_keys.append(rt._prss_keys[subset])  # send PRSS keys
+                pid_keys.extend(rt._prss_keys_to_peer(self.peer_pid))  # send PRSS keys
             transport.writelines(pid_keys)
             self._key_transport_done()
 
@@ -89,27 +84,18 @@ def data_received(self, data):
                 return
 
             peer_pid = int.from_bytes(data[:2], 'little')
-            len_packet = 2
+            del data[:2]
             rt = self.runtime
             if not rt.options.no_prss:
-                m = len(rt.parties)
-                t = rt.threshold
-                for subset in itertools.combinations(range(m), m - t):
-                    if subset[0] == peer_pid and rt.pid in subset:
-                        len_packet += 16
+                len_packet = rt._prss_keys_from_peer(peer_pid)
                 if len(data) < len_packet:
                     return
 
             # record new protocol peer
             self.peer_pid = peer_pid
             if not rt.options.no_prss:
-                # store keys received from peer
-                len_packet = 2
-                for subset in itertools.combinations(range(m), m - t):
-                    if subset[0] == peer_pid and rt.pid in subset:
-                        rt._prss_keys[subset] = data[len_packet:len_packet + 16]
-                        len_packet += 16
-            del data[:len_packet]
+                rt._prss_keys_from_peer(peer_pid, data)  # store PRSS keys from peer
+                del data[:len_packet]
             self._key_transport_done()
 
         while len(data) >= 12:
diff --git a/mpyc/mpctools.py b/mpyc/mpctools.py
index 870e561..e8b4f93 100644
--- a/mpyc/mpctools.py
+++ b/mpyc/mpctools.py
@@ -12,7 +12,8 @@
 
 runtime = None
 
-_no_value = type('', (object,), {'__repr__': lambda self: '<no value>'})
+_no_value = type('mpyc.mpctools.NoValueType', (object,), {'__repr__': lambda self: '<no value>'})()
+_no_value.__doc__ = 'Represents "empty" value, different from any other object including None.'
 
 
 def reduce(f, x, initial=_no_value):
@@ -27,8 +28,8 @@ def reduce(f, x, initial=_no_value):
     may even be of different types.
 
     If initial is provided (possibly equal to None), it is placed before the
-    items of x (hence effectively serves as a default when x is empty). If
-    initial is not given and x contains only one item, that item is returned.
+    items of x (hence effectively serves as a default when x is empty). If no
+    initial value is given and x contains only one item, that item is returned.
    """
     x = list(x)
     if initial is not _no_value:
diff --git a/mpyc/runtime.py b/mpyc/runtime.py
index 12568e8..1169795 100644
--- a/mpyc/runtime.py
+++ b/mpyc/runtime.py
@@ -108,6 +108,31 @@ def threshold(self, t):
                 keys[subset] = secrets.token_bytes(16)  # 128-bit key
         self._prss_keys = keys
 
+    def _prss_keys_to_peer(self, peer_pid):
+        """Return PRSS keys to be sent to peer."""
+        m = len(self.parties)
+        t = self.threshold
+        keys = []
+        for subset in itertools.combinations(range(m), m - t):
+            if subset[0] == self.pid and peer_pid in subset:
+                keys.append(self._prss_keys[subset])
+        return keys
+
+    def _prss_keys_from_peer(self, peer_pid, data=None):
+        """Store PRSS keys received from peer.
+
+        If data is not given, return the size of PRSS keys to be stored.
+        """
+        m = len(self.parties)
+        t = self.threshold
+        len_packet = 0
+        for subset in itertools.combinations(range(m), m - t):
+            if subset[0] == peer_pid and self.pid in subset:
+                if data is not None:
+                    self._prss_keys[subset] = data[len_packet:len_packet + 16]
+                len_packet += 16
+        return len_packet
+
     @functools.cache
     def prfs(self, bound):
         """PRFs with codomain range(bound) for pseudorandom secret sharing.