Merge pull request #6 from daira/daira-misc-improvements

Additions to .gitignore; rename CRS to URS; add test vectors for Pedersen generators

.gitignore

@@ -1 +1,8 @@
-env
+env/
+__pycache__/
+
+.*.swp
+*.*~*
+*.bak
+*.pyc
+*.pyo

sapling_generators.py

@@ -3,12 +3,13 @@ from pyblake2 import blake2s
 
 from sapling_jubjub import Point, JUBJUB_COFACTOR
 from tv_output import render_args, render_tv
+from sapling_utils import i2leosp
 
 # First 64 bytes of the BLAKE2s input during group hash.
 # This is chosen to be some random string that we couldn't have
 # anticipated when we designed the algorithm, for rigidity purposes.
 # We deliberately use an ASCII hex string of 32 bytes here.
-CRS = b'096b36a5804bfacef1691e173c366a47ff5ba84a44f26ddd7e8d9f79d5b42df0'
+URS = b'096b36a5804bfacef1691e173c366a47ff5ba84a44f26ddd7e8d9f79d5b42df0'
 
 
 #
@@ -17,7 +18,7 @@ CRS = b'096b36a5804bfacef1691e173c366a47ff5ba84a44f26ddd7e8d9f79d5b42df0'
 
 def group_hash(D, M):
     digest = blake2s(person=D)
-    digest.update(CRS)
+    digest.update(URS)
     digest.update(M)
     p = Point.from_bytes(digest.digest())
     if not p:
@@ -48,6 +49,9 @@ WINDOWED_PEDERSEN_RANDOMNESS_BASE = find_group_hash(b'Zcash_PH', b'r')
 VALUE_COMMITMENT_VALUE_BASE = find_group_hash(b'Zcash_cv', b'v')
 VALUE_COMMITMENT_RANDOMNESS_BASE = find_group_hash(b'Zcash_cv', b'r')
 
+required_bases = 4
+PEDERSEN_BASES = [find_group_hash(b'Zcash_PH', i2leosp(32, iminus1))
+                  for iminus1 in range(0, required_bases)]
 
 def main():
     render_tv(
@@ -60,6 +64,10 @@ def main():
             ('wprb', '[u8; 32]'),
             ('vcvb', '[u8; 32]'),
             ('vcrb', '[u8; 32]'),
+            ('pb0', '[u8; 32]'),
+            ('pb1', '[u8; 32]'),
+            ('pb2', '[u8; 32]'),
+            ('pb3', '[u8; 32]'),
         ),
         {
             'skb': bytes(SPENDING_KEY_BASE),
@@ -68,6 +76,10 @@ def main():
             'wprb': bytes(WINDOWED_PEDERSEN_RANDOMNESS_BASE),
             'vcvb': bytes(VALUE_COMMITMENT_VALUE_BASE),
             'vcrb': bytes(VALUE_COMMITMENT_RANDOMNESS_BASE),
+            'pb0': bytes(PEDERSEN_BASES[0]),
+            'pb1': bytes(PEDERSEN_BASES[1]),
+            'pb2': bytes(PEDERSEN_BASES[2]),
+            'pb3': bytes(PEDERSEN_BASES[3]),
         },
     )
 

tv_output.py

@@ -4,8 +4,8 @@ import json
 
 
 def chunk(h):
-    h = str(h, 'utf-8')
-    return '0x' + ', 0x'.join([h[i:i+2] for i in range(0, len(h), 2)])
+    hstr = str(h, 'utf-8')
+    return '0x' + ', 0x'.join([hstr[i:i+2] for i in range(0, len(hstr), 2)])
 
 
 #