Payment IDs can now be deterministic or non-deterministic

Also add a site salt to create them, so a given user ID will yield
different payment IDs for different sites.

README

@@ -12,7 +12,13 @@ Calling raw module functions is undocumented and subject to change.
 
  * Initialization:
 
-  monero=Monero(daemon_host,daemon_port,wallet_host,wallet_port,redis_host,redis_port)
+  monero=Monero(daemon_host,daemon_port,wallet_host,wallet_port,redis_host,redis_port,site_salt)
+
+  Site salt is a string that's specific to your particular use.
+  It should be random but constant. Its intent is to cause the
+  same recipient identifier to map to different payment IDs for
+  two different users of monero-python. It is recommended to
+  hard code some random string in the call.
 
  * Checking the current balance:
 
@@ -27,15 +33,16 @@ Calling raw module functions is undocumented and subject to change.
 
  * Create a new payment ID for a recipient:
 
-  payment_id=monero.GetPaymentID(recipient)
+  payment_id=monero.GetPaymentID(recipient,deterministic=True)
 
   recipient is a string representing a user, destination, etc. The
   semantics of it are left to the API user. Numbers can be used if
   they're passed as strings. CheckForDeposits and other such functions
   will return that recipient when the associated payment ID is found
   in a transaction.
-  Payment IDs are deterministic, so asking for a payment ID for a
-  given recipient will always yield the same payment ID.
+  Payment IDs can be deterministic (so asking for a payment ID for a
+  given recipient will always yield the same payment ID) or not (so
+  multiple calls to GetPaymentID will yield different Payment IDs).
 
  * Get the recipient corresponding to a payment ID:
 
@@ -43,7 +50,7 @@ Calling raw module functions is undocumented and subject to change.
 
   Returns the recipient associated with the given payment ID, or None
   if there is none. If there is one, it is the string that was passed
-  to a previous call to GetPaymentID.
+  to a previous call to GetPaymentID which returned this payment ID.
 
  * Check for new deposits:
 

monero/monero.py

@@ -33,18 +33,19 @@ import redisdb
 import payment
 
 class Monero:
-  def __init__(self,daemon_host,daemon_port,wallet_host,wallet_port,redis_host,redis_port):
+  def __init__(self,daemon_host,daemon_port,wallet_host,wallet_port,redis_host,redis_port,site_salt):
     redisdb.connect_to_redis(redis_host,redis_port)
     self.daemon_host=daemon_host
     self.daemon_port=daemon_port
     self.wallet_host=wallet_host
     self.wallet_port=wallet_port
+    self.site_salt=site_salt
 
   def GetWalletBalance(self):
     return utils.RetrieveWalletBalance(self.wallet_host,self.wallet_port)
 
-  def GetPaymentID(self,recipient):
-    return utils.GetPaymentIDFromUserID(recipient)
+  def GetPaymentID(self,recipient,deterministic=True):
+    return utils.GetPaymentIDFromUserID(recipient,deterministic,self.site_salt)
 
   def GetRecipient(self,payment_id):
     return utils.GetUserIDFromPaymentID(payment_id)

monero/utils.py

@@ -34,6 +34,7 @@ import json
 import httplib
 import time
 import string
+from Crypto.Random.random import getrandbits
 from decimal import *
 from log import log_error, log_warn, log_info, log_log
 from redisdb import *
@@ -45,11 +46,15 @@ cached_wallet_balance=None
 cached_wallet_unlocked_balance=None
 cached_wallet_balance_timestamp=None
 
-def GetPaymentIDFromUserID(user_id):
-  salt="nveuweaiirv-"
-  p = hashlib.sha256(salt+user_id).hexdigest()
+def GetPaymentIDFromUserID(user_id,deterministic,site_salt=''):
+  salt="nveuweaiirv-"+site_salt+'-'
+  if deterministic:
+    s = salt + user_id
+  else:
+    s = salt + str(getrandbits(128)) + '-' + user_id
+  p = hashlib.sha256(s).hexdigest()
   try:
-    redis_hset("paymentid",p,link.identity())
+    redis_hset("paymentid",p,user_id)
   except Exception,e:
     log_error('GetPaymentIDFromUserID: failed to set payment ID for %s to redis: %s' % (user_id,str(e)))
   return p