def verify(self, commitment, index_range):
"""For an object created without a private key,
check that the opened commitment verifies for at least
one NUMS point as defined by the range in index_range
"""
if not all([self.P, self.P2, self.s, self.e]):
raise PoDLEError("Verify called without sufficient data")
if not self.get_commitment() == commitment:
return False
for J in [getNUMS(i) for i in index_range]:
sig_priv = podle_PrivateKey(self.s)
sG = sig_priv.pubkey
sJ = multiply(self.s, J.serialize(), False)
e_int = decode(self.e, 256)
minus_e = encode(-e_int % N, 256, minlen=32)
minus_e_P = multiply(minus_e, self.P.serialize(), False)
minus_e_P2 = multiply(minus_e, self.P2.serialize(), False)
KGser = add_pubkeys([sG.serialize(), minus_e_P], False)
KJser = add_pubkeys([sJ, minus_e_P2], False)
#check 2: e =?= H(K_G || K_J || P || P2)
e_check = hashlib.sha256(KGser + KJser + self.P.serialize() +
self.P2.serialize()).digest()
if e_check == self.e:
return True
#commitment fails for any NUMS in the provided range
return False
def generate_podle(self, index=0, k=None):
"""Given a raw private key, in hex format,
construct a commitment sha256(P2), which is
the hash of the value x*J, where x is the private
key as a raw scalar, and J is a NUMS alternative
basepoint on the Elliptic Curve; we use J(i) where i
is an index, so as to be able to create multiple
commitments against the same privkey. The procedure
for generating the J(i) value is shown in getNUMS().
Also construct a signature (s,e) of Schnorr type,
which will serve as a zero knowledge proof that the
private key of P2 is the same as the private key of P (=x*G).
Signature is constructed as:
s = k + x*e
where k is a standard 32 byte nonce and:
e = sha256(k*G || k*J || P || P2)
Possibly Joinmarket specific comment:
Users *should* generate with lower indices first,
since verifiers will give preference to lower indices
(each verifier may have their own policy about how high
an index to allow, which really means how many reuses of utxos
to allow in Joinmarket).
Returns a commitment of form H(P2) which, note, will depend
on the index choice. Repeated calls will reset the commitment
and the associated signature data that can be used to open
the commitment.
"""
#TODO nonce could be rfc6979?
if not k:
k = os.urandom(32)
J = getNUMS(index)
KG = podle_PrivateKey(k).pubkey
KJ = multiply(k, J.serialize(), False, return_serialized=False)
self.P2 = getP2(self.priv, J)
self.get_commitment()
self.e = hashlib.sha256(''.join(
[x.serialize() for x in [KG, KJ, self.P, self.P2]])).digest()
k_int = decode(k, 256)
priv_int = decode(self.priv.private_key, 256)
e_int = decode(self.e, 256)
sig_int = (k_int + priv_int * e_int) % N
self.s = encode(sig_int, 256, minlen=32)
return self.reveal()
def __init__(self,
u=None,
priv=None,
P=None,
P2=None,
s=None,
e=None,
used=False):
#This class allows storing of utxo in format "txid:n" only for
#convenience of storage/access; it doesn't check or use the data.
#Arguments must be provided in hex.
self.u = u
if not priv:
if P:
#Construct a pubkey from raw hex
self.P = podle_PublicKey(binascii.unhexlify(P))
else:
self.P = None
else:
if P:
raise PoDLEError("Pubkey should not be provided with privkey")
#any other formatting abnormality will just throw in PrivateKey
if len(priv) == 66 and priv[-2:] == '01':
priv = priv[:-2]
self.priv = podle_PrivateKey(binascii.unhexlify(priv))
self.P = self.priv.pubkey
if P2:
self.P2 = podle_PublicKey(binascii.unhexlify(P2))
else:
self.P2 = None
#These sig values should be passed in hex.
self.s = None
self.e = None
if s:
self.s = binascii.unhexlify(s)
if e:
self.e = binascii.unhexlify(e)
#Optionally maintain usage state (boolean)
self.used = used
#the H(P2) value
self.commitment = None