class Agent(object):
'''
Simulated claimchain user in the online deployment mode.
'''
def __init__(self, email):
self.email = email
self.params = LocalParams.generate()
self.chain_store = ObjectStore()
self.tree_store = ObjectStore()
self.chain = Chain(self.chain_store)
self.state = State()
# Stats
self.nb_sent_emails = 0
# Committed views and capabilities
self.committed_caps = {}
self.committed_views = {}
# ...and the ones queued to be committed.
self.queued_identity_info = None
self.queued_caps = defaultdict(set)
self.queued_views = {}
# Capabilities for unknown yet contacts
# and views that have no readers.
self.expected_caps = defaultdict(set)
self.expected_views = defaultdict(set)
# Known beliefs of other people about other people.
self.global_views = defaultdict(dict)
# Contacts that senders have made available to this agent.
self.contacts_by_sender = defaultdict(set)
# Objects that were sent to each recipient.
self.sent_object_keys_to_recipients = {}
# Objects that were received from other people.
self.gossip_store = ObjectStore()
# Generate initial encryption key, and add first block
# to the chain
self.update_key()
@property
def head(self):
return self.chain.head
@property
def current_enc_key(self):
"""
Current encryption key
"""
return self.state.identity_info
@staticmethod
def generate_public_key():
"""
Generate (fake) public encryption key
"""
# 4096 random bits in base64
return base64.b64encode(os.urandom(4096 // 8))
def add_expected_reader(self, reader, contacts):
"""
Add contacts to be accessible by the reader
No need to know the reader's DH key, and contact
views at this point. As soon as these will be learned,
expected capabilities will be moved to the queue.
"""
if isinstance(contacts, six.string_types):
warnings.warn("Contacts is a string type, an iterable of "
"identifiers is expected.")
if not contacts:
return
logger.debug('%s / expected cap / %s: %s', self.email, reader,
contacts)
self.expected_caps[reader].update(contacts)
def _update_buffer(self):
accepted_caps_by_reader = defaultdict(set)
for reader, contacts in self.expected_caps.items():
reader_view = self.get_latest_view(reader)
if reader_view is None and reader != PUBLIC_READER_LABEL:
continue
for contact in contacts:
contact_view = self.get_latest_view(contact)
if contact_view is not None:
# Copy expected cap into queue.
self.queued_caps[reader].add(contact)
# Move expected view into queue if needed.
if contact in self.expected_views:
self.queued_views[contact] = contact_view
del self.expected_views[contact]
accepted_caps_by_reader[reader].add(contact)
# Move reader view into queue if needed.
if accepted_caps_by_reader[reader]:
if reader in self.expected_views:
self.queued_views[reader] = reader_view
del self.expected_views[reader]
# Clean empty expected_caps entries.
for reader, contacts in accepted_caps_by_reader.items():
self.expected_caps[reader] -= contacts
if not self.expected_caps[reader]:
del self.expected_caps[reader]
def get_latest_view(self, contact, save=True):
"""
Resolve latest view for contact through social policy
The method gathers candidate views for contact across local state,
and runs social validation policy to decide on the best candidate.
As a side effect, puts the resolved view in the queue.
:param contact: Contact identifier
:param save: Whether to save the resolved view to the queue
"""
policy = AgentSettings.get_default().conflict_resolution_policy
# Collect possible candidates
candidate_views = set()
# ...starting with existing views of the contact.
if contact in self.committed_views:
candidate_views.add(self.committed_views[contact])
if contact in self.queued_views:
candidate_views.add(self.queued_views[contact])
if contact in self.expected_views:
candidate_views.add(self.expected_views[contact])
# Get a view of contact in question from every friend.
current_friends = set(self.committed_views.keys()) \
| set(self.queued_views.keys()) \
| set(self.expected_views.keys())
for friend in current_friends - {contact}:
candidate_view = self.global_views[friend].get(contact)
if candidate_view is not None:
candidate_views.add(candidate_view)
# If no candidates, return None.
if len(candidate_views) == 0:
return None
# Otherwise, resolve conflicts using a policy
view = policy(self, candidate_views)
# ...and add the resolved view to the queue.
self.expected_views[contact] = view
# Remove from queue if resolved view is the same as committed.
if save:
committed_view = self.committed_views.get(contact)
if view == committed_view:
del self.expected_views[contact]
return view
def send_message(self, recipients):
"""
Compute additional data to be sent to recipients
NOTE: May update the chain if required by the update policy
:param recipients: An iterable of recipient identifiers (emails)
:returns: ``MessageMetadata`` object
"""
logger.debug('%s -> %s', self.email, recipients)
if len(recipients) == 0:
return
if isinstance(recipients, six.string_types):
warnings.warn("Recipients is a string type, an iterable of "
"identifiers is expected.")
if not isinstance(recipients, set):
recipients = set(recipients)
with self.params.as_default():
intro_policy = AgentSettings.get_default().introduction_policy
# Grant accesses according to introduction policy.
intro_policy(self, recipients)
# Move expected views and caps into queue
self._update_buffer()
# Decide whether to update the encryption key.
# TODO: Make key update decision a policy.
nb_sent_emails_thresh = AgentSettings.get_default() \
.key_update_every_nb_sent_emails
if nb_sent_emails_thresh is not None and \
self.nb_sent_emails > nb_sent_emails_thresh:
self.update_key()
else:
# Decide whether to update the chain.
update_policy = AgentSettings.get_default().chain_update_policy
if update_policy(self, recipients):
self.update_chain()
local_object_keys = set()
global_object_keys = set()
# Add own chain blocks.
# NOTE: Requires that chain and tree use separate stores
local_object_keys.update(self.chain_store.keys())
# Add evidence for public claims.
public_contacts = self.committed_caps.get(PUBLIC_READER_LABEL) \
or set()
for contact in public_contacts:
object_keys = self.state.compute_evidence_keys(
PUBLIC_READER_PARAMS.dh.pk, contact)
local_object_keys.update(object_keys)
contact_view = self.committed_views.get(contact)
if contact_view is not None:
global_object_keys.add(contact_view.head)
# Compute evidence that needs to be sent to all recipients.
for recipient in recipients:
# NOTE: This assumes that claims contain heads
accessible_contacts = self.committed_caps.get(recipient) \
or set()
for contact in accessible_contacts:
recipient_view = self.committed_views.get(recipient)
if recipient_view is None:
continue
contact_view = self.committed_views.get(contact)
if contact_view is not None:
# Add evidence for cross-references.
recipient_dh_pk = recipient_view.params.dh.pk
evidence_keys = self.state.compute_evidence_keys(
recipient_dh_pk, contact)
local_object_keys.update(evidence_keys)
# Add contact's latest block.
global_object_keys.add(contact_view.head)
# Compute the minimal amount of objects that need to be sent in
# this message.
relevant_keys = local_object_keys | global_object_keys
object_keys_to_send = set()
for recipient in recipients:
if recipient not in self.sent_object_keys_to_recipients:
self.sent_object_keys_to_recipients[recipient] = \
relevant_keys
object_keys_to_send = relevant_keys
else:
object_keys_for_recipient = relevant_keys.difference(
self.sent_object_keys_to_recipients[recipient])
object_keys_to_send |= object_keys_for_recipient
# Gather the objects by keys.
message_store = {}
for key in local_object_keys.intersection(object_keys_to_send):
value = self.chain_store.get(key) or self.tree_store.get(key)
if value is not None:
message_store[key] = value
for key in global_object_keys.intersection(object_keys_to_send):
value = self.gossip_store.get(key)
if value is not None:
message_store[key] = value
self.nb_sent_emails += 1
return MessageMetadata(self.chain.head, public_contacts,
message_store)
def get_accessible_contacts(self,
sender,
message_metadata,
other_recipients=None):
"""
Get the contacts that are expected to be accessible on sender's chain
"""
# NOTE: Assumes other people's introduction policy is the same
contacts = self.contacts_by_sender[sender]
other_recipients = set(other_recipients) - {sender, self.email}
for recipient in other_recipients | message_metadata.public_contacts:
contacts.add(recipient)
return contacts
def receive_message(self, sender, message_metadata, other_recipients=None):
"""
Interpret incoming additional data
:param sender: Sender identifier
:param message_metadata: Additional data obtained by ``send_message``
:param other_recipients: Identifiers of other known recipients of the
message
"""
logger.debug('%s <- %s', self.email, sender)
if other_recipients is None:
other_recipients = set()
with self.params.as_default():
# Merge stores temporarily.
merged_store = ObjectStore(self.gossip_store)
for key, obj in message_metadata.store.items():
merged_store[key] = obj
sender_head = message_metadata.head
sender_latest_block = merged_store[sender_head]
self.gossip_store[sender_head] = \
sender_latest_block
self.expected_views[sender] = View(
Chain(self.gossip_store, root_hash=sender_head))
full_sender_view = View(Chain(merged_store, root_hash=sender_head))
logger.debug('%s / expected view / %s', self.email, sender)
# Add relevant objects from the message store.
contacts = self.get_accessible_contacts(sender, message_metadata,
other_recipients)
for contact in contacts - {self.email}:
contact_head = self.get_contact_head_from_view(
full_sender_view, contact)
if contact_head is None:
continue
contact_latest_block = message_metadata.store.get(contact_head)
if contact_latest_block is not None:
self.gossip_store[contact_head] = contact_latest_block
# NOTE: Assumes people send only contacts' latest blocks
contact_chain = Chain(self.gossip_store,
root_hash=contact_head)
self.global_views[sender][contact] = View(contact_chain)
# TODO: Needs a special check for contact==self.email.
# Recompute the latest beliefs.
for contact in {sender} | contacts:
self.get_latest_view(contact)
def get_contact_head_from_view(self, view, contact):
"""
Try accessing cross-reference claim as yourself, and as a public reader
:param view: View to query
:param contact: Contact of interest
:returns: Contacts head, or None
"""
with self.params.as_default():
claim = view.get(contact)
if claim is not None:
return claim
with PUBLIC_READER_PARAMS.as_default():
claim = view.get(contact)
return claim
def update_chain(self):
"""
Force chain update
Commits views and capabilities in the queues to the chain
"""
logger.debug('%s / chain update', self.email)
with self.params.as_default():
# Refresh views of all friends and contacts in queued capabilities.
for friend, contacts in self.queued_caps.items():
self.get_latest_view(friend)
for contact in contacts:
self.get_latest_view(contact)
# Add the latest own encryption key.
if self.queued_identity_info is not None:
self.state.identity_info = self.queued_identity_info
# Get heads of queued views into the claimchain state.
for friend, view in self.queued_views.items():
claim = view.chain.head
if claim is not None:
self.state[friend] = claim
self.committed_views[friend] = view
# Get capabilities in the capability queue into the claimchain
# state, for those subjects whose keys are known.
for friend, contacts in self.queued_caps.items():
if len(contacts) == 0:
continue
friend_dh_pk = None
# If the buffer is for the public 'reader':
if friend == PUBLIC_READER_LABEL:
friend_dh_pk = PUBLIC_READER_PARAMS.dh.pk
# Otherwise, try to find the DH key in views.
else:
view = self.get_latest_view(friend, save=False)
if view is not None:
friend_dh_pk = view.params.dh.pk
if friend_dh_pk is not None:
self.state.grant_access(friend_dh_pk, contacts)
if friend in self.committed_caps:
self.committed_caps[friend].update(contacts)
else:
self.committed_caps[friend] = set(contacts)
else:
# This should not happen
raise warnings.warn('Cap reader DH key not known at the '
'time of committing.')
# Commit state
head = self.state.commit(target_chain=self.chain,
tree_store=self.tree_store)
# Flush the view and caps queues
self.queued_views.clear()
self.queued_caps.clear()
def update_key(self):
"""
Force update of the encryption key, and the chain
"""
logger.debug('%s / key update', self.email)
self.queued_identity_info = Agent.generate_public_key()
self.update_chain()
def __repr__(self):
return 'Agent("%s")' % self.email
class Agent(object):
"""
Simulated ClaimChain user.
"""
def __init__(self, email):
self.email = email
self.params = LocalParams.generate()
self.chain_store = ObjectStore()
self.tree_store = ObjectStore()
self.chain = Chain(self.chain_store)
self.state = State()
# Stats
self.nb_sent_emails = 0
self.date_of_last_key_update = None
# Committed views and capabilities
self.committed_caps = {}
self.committed_views = {}
# ...and the ones queued to be committed.
self.queued_identity_info = None
self.queued_caps = defaultdict(set)
self.queued_views = {}
# Capabilities for unknown yet contacts
# and views that have no readers.
self.expected_caps = defaultdict(set)
self.expected_views = defaultdict(set)
# Known beliefs of other people about other people.
self.global_views = defaultdict(dict)
# Contacts that senders have made available to this agent.
self.contacts_by_sender = defaultdict(set)
# Objects that were sent to each recipient.
self.sent_object_keys_to_recipients = {}
# Objects that were received from other people.
self.gossip_store = ObjectStore()
# Generate initial encryption key, and add first block
# to the chain
self.update_key()
@property
def head(self):
"""Chain head."""
return self.chain.head
@property
def current_enc_key(self):
"""
Current encryption key.
"""
return self.state.identity_info
@staticmethod
def generate_public_key():
"""
Generate (fake) public encryption key.
"""
# 4096 random bits in base64
return base64.b64encode(os.urandom(4096 // 8))
def add_expected_reader(self, reader, contacts):
"""
Make contacts accessible to the reader.
No need to know the reader's DH key, and contact
views at this point. As soon as these will be learned,
expected capabilities will be moved to the queue.
"""
if isinstance(contacts, six.string_types):
# Quick check to prevent a silly bug.
warnings.warn("Contacts is a string type, an iterable of "
"identifiers is expected.")
if not contacts:
return
logger.debug('%s / expected cap / %s: %s', self.email, reader,
contacts)
self.expected_caps[reader].update(contacts)
def _update_buffer(self):
"""Update claim 'expected' and 'queued' buffers.
Traverses all claims in the 'expected' buffer, and checks if there
has been collected enough information to actually make the claims.
Those for which the information in the gossip store is sufficient,
are moved to the 'queued' buffer.
"""
accepted_caps_by_reader = defaultdict(set)
for reader, contacts in self.expected_caps.items():
reader_view = self.get_latest_view(reader)
if reader_view is None and reader != PUBLIC_READER_LABEL:
continue
for contact in contacts:
contact_view = self.get_latest_view(contact)
if contact_view is not None:
# Copy expected cap into queue.
self.queued_caps[reader].add(contact)
# Move the expected view into queue if needed.
if contact in self.expected_views:
self.queued_views[contact] = contact_view
del self.expected_views[contact]
accepted_caps_by_reader[reader].add(contact)
# Move the reader view into queue if needed.
if accepted_caps_by_reader[reader]:
if reader in self.expected_views:
self.queued_views[reader] = reader_view
del self.expected_views[reader]
# Clean empty expected_caps entries.
for reader, contacts in accepted_caps_by_reader.items():
self.expected_caps[reader] -= contacts
if not self.expected_caps[reader]:
del self.expected_caps[reader]
def get_social_evidence(self, contact):
"""Gather social evidence about the contact."""
# Collect possible candidates
own_views = set()
# ...starting with existing views of the contact.
if contact in self.committed_views:
own_views.add(self.committed_views[contact])
if contact in self.queued_views:
own_views.add(self.queued_views[contact])
if contact in self.expected_views:
own_views.add(self.expected_views[contact])
# Get a view of the contact in question from every friend.
current_friends = set(self.committed_views.keys()) \
| set(self.queued_views.keys()) \
| set(self.expected_views.keys())
views_by_friend = {}
for friend in current_friends - {contact, self.email}:
candidate_view = self.global_views[friend].get(contact)
if candidate_view is not None:
views_by_friend[friend] = candidate_view
return own_views, views_by_friend
def get_latest_view(self, contact, save=True):
"""Resolve latest view for contact through a social policy.
Gathers candidate views for contact across local state, and runs
a social validation policy to decide on the best candidate.
As a side effect, puts the resolved view in the 'expected' buffer.
:param contact: Contact identifier
:param bool save: Whether to save the resolved view to the queue
"""
own_views, views_by_friend = self.get_social_evidence(contact)
policy = AgentSettings.get_default().conflict_resolution_policy
candidate_views = own_views | set(views_by_friend.values())
if len(candidate_views) == 0:
return None
# Resolve conflicts using a policy
view = policy(self, candidate_views)
# ...and add the resolved view to the 'expected' buffer.
self.expected_views[contact] = view
# Remove from the buffer if the resolved view is the same as committed.
if save:
committed_view = self.committed_views.get(contact)
if view == committed_view:
del self.expected_views[contact]
return view
def send_message(self, recipients, mtime=0):
"""Build an ClaimChain embedded data packet.
NOTE: May update the chain if required by the update policy.
:param recipients: An iterable of recipient identifiers (emails)
:param mtime: Timestamp
:returns: ``MessageMetadata`` object
"""
logger.debug('%s -> %s', self.email, recipients)
if len(recipients) == 0:
return
if isinstance(recipients, six.string_types):
warnings.warn("Recipients is a string type, an iterable of "
"identifiers is expected.")
if not isinstance(recipients, set):
recipients = set(recipients)
with self.params.as_default():
intro_policy = AgentSettings.get_default().introduction_policy
# Grant accesses according to the introduction policy.
intro_policy(self, recipients)
# Move expected views and caps into the queue.
self._update_buffer()
# Decide whether to update the encryption key.
# TODO: Make key update decision a policy.
nb_sent_emails_thresh = AgentSettings.get_default() \
.key_update_every_nb_sent_emails
min_nb_days = AgentSettings.get_default() \
.key_update_every_nb_days
nb_sent_based_update = nb_sent_emails_thresh is not None and \
self.nb_sent_emails >= nb_sent_emails_thresh
time_based_update = False
sending_date = datetime.fromtimestamp(mtime)
if self.date_of_last_key_update is not None:
days_since_last_update = (sending_date -
self.date_of_last_key_update).days
if min_nb_days is not None:
time_based_update = days_since_last_update >= min_nb_days
time_based_update = min_nb_days is not None and (
days_since_last_update >= min_nb_days)
else:
self.date_of_last_key_update = sending_date
if nb_sent_based_update or time_based_update:
self.update_key(mtime)
self.nb_sent_emails = 0
else:
# Decide whether to update the chain.
update_policy = AgentSettings.get_default().chain_update_policy
if update_policy(self, recipients):
self.update_chain()
local_object_keys = set()
# Add own chain blocks.
# NOTE: Requires that chain and tree use separate stores
local_object_keys.update(self.chain_store.keys())
# Add authentication proofs for public claims.
public_contacts = self.committed_caps.get(PUBLIC_READER_LABEL) \
or set()
for contact in public_contacts:
object_keys = self.state.compute_evidence_keys(
PUBLIC_READER_PARAMS.dh.pk, contact)
local_object_keys.update(object_keys)
contact_view = self.committed_views.get(contact)
# Find a minimal amount of proof nodes that need to be included.
for recipient in recipients:
accessible_contacts = self.committed_caps.get(recipient) \
or set()
for contact in accessible_contacts:
recipient_view = self.committed_views.get(recipient)
if recipient_view is None:
continue
contact_view = self.committed_views.get(contact)
if contact_view is not None:
# Add the proof for the cross-reference.
recipient_dh_pk = recipient_view.params.dh.pk
proof_keys = self.state.compute_evidence_keys(
recipient_dh_pk, contact)
local_object_keys.update(proof_keys)
# Find the minimal amount of objects that need to be sent in
# this message.
relevant_keys = local_object_keys
object_keys_to_send = set()
for recipient in recipients:
if recipient not in self.sent_object_keys_to_recipients:
if AgentSettings.get_default().optimize_sent_objects:
self.sent_object_keys_to_recipients[recipient] = \
relevant_keys
object_keys_to_send = relevant_keys
else:
object_keys_for_recipient = relevant_keys.difference(
self.sent_object_keys_to_recipients[recipient])
object_keys_to_send |= object_keys_for_recipient
# Collect the objects by keys.
message_store = {}
# * Local (own) objects...
for key in local_object_keys.intersection(object_keys_to_send):
value = self.chain_store.get(key) or self.tree_store.get(key)
if value is not None:
message_store[key] = value
self.nb_sent_emails += 1
return MessageMetadata(self.chain.head, public_contacts,
message_store)
def get_accessible_contacts(self,
sender,
message_metadata,
other_recipients=None):
"""
Get the contacts that are expected to be accessible on sender's chain.
"""
# NOTE: Assumes other people's introduction policy is the same
contacts = self.contacts_by_sender[sender]
other_recipients = set(other_recipients) - {sender, self.email}
for recipient in other_recipients | message_metadata.public_contacts:
contacts.add(recipient)
return contacts
def receive_message(self, sender, message_metadata, other_recipients=None):
"""Interpret an incoming data packet.
:param sender: Sender identifier
:param message_metadata: Additional data obtained by ``send_message``
:param other_recipients: Identifiers of other known recipients of the
message
"""
logger.debug('%s <- %s', self.email, sender)
if other_recipients is None:
other_recipients = set()
with self.params.as_default():
# Merge stores temporarily.
merged_store = ObjectStore(self.gossip_store)
for key, obj in message_metadata.store.items():
merged_store[key] = obj
sender_head = message_metadata.head
sender_latest_block = merged_store[sender_head]
self.gossip_store[sender_head] = \
sender_latest_block
self.expected_views[sender] = View(
Chain(self.gossip_store, root_hash=sender_head))
full_sender_view = View(Chain(merged_store, root_hash=sender_head))
logger.debug('%s / expected view / %s', self.email, sender)
# Add relevant objects from the message store.
contacts = self.get_accessible_contacts(sender, message_metadata,
other_recipients)
for contact in contacts - {self.email}:
contact_latest_block = self.get_contact_head_from_view(
full_sender_view, contact)
if contact_latest_block is not None:
contact_head_hash = contact_latest_block.hid
self.gossip_store[contact_head_hash] = contact_latest_block
# NOTE: Assumes people send only contacts' latest blocks
contact_chain = Chain(self.gossip_store,
root_hash=contact_head_hash)
self.global_views[sender][contact] = View(contact_chain)
# TODO: Needs a special check for contact==self.email.
# Recompute the latest beliefs.
for contact in {sender} | contacts:
self.get_latest_view(contact)
def get_contact_head_from_view(self, view, contact):
"""
Try accessing a claim as oneself, and fall back to a public reader.
:param view: View to query
:param contact: Contact of interest
:returns: Contact's head block, or None
"""
with self.params.as_default():
claim = view.get(contact)
if claim is not None:
return deserialize_block(claim)
with PUBLIC_READER_PARAMS.as_default():
claim = view.get(contact)
if claim is not None:
return deserialize_block(claim)
def update_chain(self):
"""Force a chain update.
Commits views and capabilities in the queues to the chain.
"""
logger.debug('%s / chain update', self.email)
with self.params.as_default():
# Refresh views of all friends and contacts in queued capabilities.
for friend, contacts in self.queued_caps.items():
self.get_latest_view(friend)
for contact in contacts:
self.get_latest_view(contact)
# Add the latest own encryption key.
if self.queued_identity_info is not None:
self.state.identity_info = self.queued_identity_info
# Mark queued views as committed.
for friend, view in self.queued_views.items():
self.committed_views[friend] = view
# Put heads of previously committed views into the state.
for friend, view in self.committed_views.items():
latest_block = view.chain.store.get(view.head)
self.state[friend] = serialize_block(latest_block)
self.committed_views[friend] = view
# Collect DH keys for all readers.
dh_pk_by_reader = {}
readers = set(self.queued_caps.keys()) | self.committed_caps.keys()
for reader in readers:
reader_dh_pk = None
# If the buffer is for the public reader:
if reader == PUBLIC_READER_LABEL:
reader_dh_pk = PUBLIC_READER_PARAMS.dh.pk
# Otherwise, try to find the DH key in views.
else:
view = self.get_latest_view(reader, save=False)
if view is not None:
reader_dh_pk = view.params.dh.pk
if reader_dh_pk is not None:
dh_pk_by_reader[reader] = reader_dh_pk
# Grant the accesses.
for reader, contacts in self.queued_caps.items():
if len(contacts) == 0:
continue
if reader in self.committed_caps:
self.committed_caps[reader].update(contacts)
else:
self.committed_caps[reader] = set(contacts)
for reader, reader_dh_pk in dh_pk_by_reader.items():
contacts = self.committed_caps.get(reader)
if contacts:
self.state.grant_access(reader_dh_pk, contacts)
# Commit state.
head = self.state.commit(target_chain=self.chain,
tree_store=self.tree_store)
# Flush the view and caps queues.
self.queued_views.clear()
self.queued_caps.clear()
def update_key(self, mtime=None):
"""
Force update of the encryption key, and the chain.
"""
logger.debug('%s / key update', self.email)
self.queued_identity_info = Agent.generate_public_key()
self.update_chain()
if mtime is not None:
self.date_of_last_key_update = datetime.fromtimestamp(mtime)
def __repr__(self):
return 'Agent("%s")' % self.email