Imported Upstream version 0.9.2upstream/0.9.2

1 files changed, 1497 insertions, 0 deletions

diff --git a/src/nse/gnunet-service-nse.c b/src/nse/gnunet-service-nse.c
new file mode 100644
index 0000000..3af9bb7
--- /dev/null
+++ b/src/nse/gnunet-service-nse.c
@@ -0,0 +1,1497 @@
+/*
+  This file is part of GNUnet.
+  (C) 2009, 2010, 2011 Christian Grothoff (and other contributing authors)
+
+  GNUnet is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published
+  by the Free Software Foundation; either version 3, or (at your
+  option) any later version.
+
+  GNUnet is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with GNUnet; see the file COPYING.  If not, write to the
+  Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+  Boston, MA 02111-1307, USA.
+ */
+
+/**
+ * @file nse/gnunet-service-nse.c
+ * @brief network size estimation service
+ * @author Nathan Evans
+ * @author Christian Grothoff
+ *
+ * The purpose of this service is to estimate the size of the network.
+ * Given a specified interval, each peer hashes the most recent
+ * timestamp which is evenly divisible by that interval.  This hash is
+ * compared in distance to the peer identity to choose an offset.  The
+ * closer the peer identity to the hashed timestamp, the earlier the
+ * peer sends out a "nearest peer" message.  The closest peer's
+ * message should thus be received before any others, which stops
+ * those peer from sending their messages at a later duration.  So
+ * every peer should receive the same nearest peer message, and from
+ * this can calculate the expected number of peers in the network.
+ */
+#include "platform.h"
+#include <math.h>
+#include "gnunet_util_lib.h"
+#include "gnunet_constants.h"
+#include "gnunet_protocols.h"
+#include "gnunet_signatures.h"
+#include "gnunet_statistics_service.h"
+#include "gnunet_core_service.h"
+#include "gnunet_nse_service.h"
+#include "nse.h"
+
+/**
+ * Should messages be delayed randomly?  This option should be set to
+ * GNUNET_NO only for experiments, not in production.  It should also
+ * be removed once the initial experiments have been completed.
+ */
+#define USE_RANDOM_DELAYS GNUNET_YES
+
+/**
+ * Should we generate a histogram with the time stamps of when we received
+ * NSE messages to disk? (for performance evaluation only, not useful in
+ * production).  The associated code should also probably be removed
+ * once we're done with experiments.
+ */
+#define ENABLE_HISTOGRAM GNUNET_NO
+
+/**
+ * Over how many values do we calculate the weighted average?
+ */
+#define HISTORY_SIZE 64
+
+/**
+ * Message priority to use.
+ */
+#define NSE_PRIORITY 5
+
+#if FREEBSD
+#define log2(a) (log(a)/log(2))
+#endif
+
+/**
+ * Amount of work required (W-bit collisions) for NSE proofs, in collision-bits.
+ */
+static unsigned long long nse_work_required;
+
+/**
+ * Interval for sending network size estimation flood requests.
+ */
+static struct GNUNET_TIME_Relative gnunet_nse_interval;
+
+/**
+ * Interval between proof find runs.
+ */
+static struct GNUNET_TIME_Relative proof_find_delay;
+
+#if ENABLE_HISTOGRAM
+/**
+ * Handle for writing when we received messages to disk.
+ */
+static struct GNUNET_BIO_WriteHandle *wh;
+#endif
+
+
+/**
+ * Per-peer information.
+ */
+struct NSEPeerEntry
+{
+
+  /**
+   * Core handle for sending messages to this peer.
+   */
+  struct GNUNET_CORE_TransmitHandle *th;
+
+  /**
+   * What is the identity of the peer?
+   */
+  struct GNUNET_PeerIdentity id;
+
+  /**
+   * Task scheduled to send message to this peer.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier transmit_task;
+
+  /**
+   * Did we receive or send a message about the previous round
+   * to this peer yet?   GNUNET_YES if the previous round has
+   * been taken care of.
+   */
+  int previous_round;
+
+#if ENABLE_HISTOGRAM
+
+  /**
+   * Amount of messages received from this peer on this round.
+   */
+  unsigned int received_messages;
+
+  /**
+   * Amount of messages transmitted to this peer on this round.
+   */
+  unsigned int transmitted_messages;
+
+  /**
+   * Which size did we tell the peer the network is?
+   */
+  unsigned int last_transmitted_size;
+
+#endif
+
+};
+
+
+GNUNET_NETWORK_STRUCT_BEGIN
+
+/**
+ * Network size estimate reply; sent when "this"
+ * peer's timer has run out before receiving a
+ * valid reply from another peer.
+ */
+struct GNUNET_NSE_FloodMessage
+{
+  /**
+   * Type: GNUNET_MESSAGE_TYPE_NSE_P2P_FLOOD
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Number of hops this message has taken so far.
+   */
+  uint32_t hop_count GNUNET_PACKED;
+
+  /**
+   * Purpose.
+   */
+  struct GNUNET_CRYPTO_RsaSignaturePurpose purpose;
+
+  /**
+   * The current timestamp value (which all
+   * peers should agree on).
+   */
+  struct GNUNET_TIME_AbsoluteNBO timestamp;
+
+  /**
+   * Number of matching bits between the hash
+   * of timestamp and the initiator's public
+   * key.
+   */
+  uint32_t matching_bits GNUNET_PACKED;
+
+  /**
+   * Public key of the originator.
+   */
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded pkey;
+
+  /**
+   * Proof of work, causing leading zeros when hashed with pkey.
+   */
+  uint64_t proof_of_work GNUNET_PACKED;
+
+  /**
+   * Signature (over range specified in purpose).
+   */
+  struct GNUNET_CRYPTO_RsaSignature signature;
+};
+GNUNET_NETWORK_STRUCT_END
+
+/**
+ * Handle to our current configuration.
+ */
+static const struct GNUNET_CONFIGURATION_Handle *cfg;
+
+/**
+ * Handle to the statistics service.
+ */
+static struct GNUNET_STATISTICS_Handle *stats;
+
+/**
+ * Handle to the core service.
+ */
+static struct GNUNET_CORE_Handle *coreAPI;
+
+/**
+ * Map of all connected peers.
+ */
+static struct GNUNET_CONTAINER_MultiHashMap *peers;
+
+/**
+ * The current network size estimate.  Number of bits matching on
+ * average thus far.
+ */
+static double current_size_estimate;
+
+/**
+ * The standard deviation of the last HISTORY_SIZE network
+ * size estimates.
+ */
+static double current_std_dev = NAN;
+
+/**
+ * Current hop counter estimate (estimate for network diameter).
+ */
+static uint32_t hop_count_max;
+
+/**
+ * Message for the next round, if we got any.
+ */
+static struct GNUNET_NSE_FloodMessage next_message;
+
+/**
+ * Array of recent size estimate messages.
+ */
+static struct GNUNET_NSE_FloodMessage size_estimate_messages[HISTORY_SIZE];
+
+/**
+ * Index of most recent estimate.
+ */
+static unsigned int estimate_index;
+
+/**
+ * Number of valid entries in the history.
+ */
+static unsigned int estimate_count;
+
+/**
+ * Task scheduled to update our flood message for the next round.
+ */
+static GNUNET_SCHEDULER_TaskIdentifier flood_task;
+
+/**
+ * Task scheduled to compute our proof.
+ */
+static GNUNET_SCHEDULER_TaskIdentifier proof_task;
+
+/**
+ * Notification context, simplifies client broadcasts.
+ */
+static struct GNUNET_SERVER_NotificationContext *nc;
+
+/**
+ * The next major time.
+ */
+static struct GNUNET_TIME_Absolute next_timestamp;
+
+/**
+ * The current major time.
+ */
+static struct GNUNET_TIME_Absolute current_timestamp;
+
+/**
+ * The public key of this peer.
+ */
+static struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded my_public_key;
+
+/**
+ * The private key of this peer.
+ */
+static struct GNUNET_CRYPTO_RsaPrivateKey *my_private_key;
+
+/**
+ * The peer identity of this peer.
+ */
+static struct GNUNET_PeerIdentity my_identity;
+
+/**
+ * Proof of work for this peer.
+ */
+static uint64_t my_proof;
+
+
+/**
+ * Initialize a message to clients with the current network
+ * size estimate.
+ *
+ * @param em message to fill in
+ */
+static void
+setup_estimate_message (struct GNUNET_NSE_ClientMessage *em)
+{
+  unsigned int i;
+  unsigned int j;
+  double mean;
+  double sum;
+  double std_dev;
+  double variance;
+  double val;
+  double nsize;
+
+#define WEST 1
+  /* Weighted incremental algorithm for stddev according to West (1979) */
+#if WEST
+  double sumweight;
+  double weight;
+  double q;
+  double r;
+  double temp;
+
+  mean = 0.0;
+  sum = 0.0;
+  sumweight = 0.0;
+  variance = 0.0;
+  for (i = 0; i < estimate_count; i++)
+  {
+    j = (estimate_index - i + HISTORY_SIZE) % HISTORY_SIZE;
+    val = htonl (size_estimate_messages[j].matching_bits);
+    weight = estimate_count + 1 - i;
+
+    temp = weight + sumweight;
+    q = val - mean;
+    r = q * weight / temp;
+    mean += r;
+    sum += sumweight * q * r;
+    sumweight = temp;
+  }
+  if (estimate_count > 0)
+    variance = (sum / sumweight) * estimate_count / (estimate_count - 1.0);
+#else
+  /* trivial version for debugging */
+  double vsq;
+
+  /* non-weighted trivial version */
+  sum = 0.0;
+  vsq = 0.0;
+  variance = 0.0;
+  mean = 0.0;
+
+  for (i = 0; i < estimate_count; i++)
+  {
+    j = (estimate_index - i + HISTORY_SIZE) % HISTORY_SIZE;
+    val = htonl (size_estimate_messages[j].matching_bits);
+    sum += val;
+    vsq += val * val;
+  }
+  if (0 != estimate_count)
+  {
+    mean = sum / estimate_count;
+    variance = (vsq - mean * sum) / (estimate_count - 1.0);     // terrible for numerical stability...
+  }
+#endif
+  if (variance >= 0)
+    std_dev = sqrt (variance);
+  else
+    std_dev = variance;         /* must be infinity due to estimate_count == 0 */
+  current_std_dev = std_dev;
+  current_size_estimate = mean;
+
+  em->header.size = htons (sizeof (struct GNUNET_NSE_ClientMessage));
+  em->header.type = htons (GNUNET_MESSAGE_TYPE_NSE_ESTIMATE);
+  em->reserved = htonl (0);
+  em->timestamp = GNUNET_TIME_absolute_hton (GNUNET_TIME_absolute_get ());
+  double se = mean - 0.332747;
+  nsize = log2 (GNUNET_CONTAINER_multihashmap_size (peers) + 1);
+  em->size_estimate = GNUNET_hton_double (GNUNET_MAX (se, nsize));
+  em->std_deviation = GNUNET_hton_double (std_dev);
+  GNUNET_STATISTICS_set (stats, "# nodes in the network (estimate)",
+                         (uint64_t) pow (2, mean - 1.0 / 3.0), GNUNET_NO);
+}
+
+
+/**
+ * Handler for START message from client, triggers an
+ * immediate current network estimate notification.
+ * Also, we remember the client for updates upon future
+ * estimate measurements.
+ *
+ * @param cls unused
+ * @param client who sent the message
+ * @param message the message received
+ */
+static void
+handle_start_message (void *cls, struct GNUNET_SERVER_Client *client,
+                      const struct GNUNET_MessageHeader *message)
+{
+  struct GNUNET_NSE_ClientMessage em;
+
+#if DEBUG_NSE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Received START message from client\n");
+#endif
+  GNUNET_SERVER_notification_context_add (nc, client);
+  setup_estimate_message (&em);
+  GNUNET_SERVER_notification_context_unicast (nc, client, &em.header,
+                                              GNUNET_YES);
+  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+}
+
+
+/**
+ * How long should we delay a message to go the given number of
+ * matching bits?
+ *
+ * @param matching_bits number of matching bits to consider
+ */
+static double
+get_matching_bits_delay (uint32_t matching_bits)
+{
+  /* Calculated as: S + f/2 - (f / pi) * (atan(x - p')) */
+  // S is next_timestamp (ignored in return value)
+  // f is frequency (gnunet_nse_interval)
+  // x is matching_bits
+  // p' is current_size_estimate
+  return ((double) gnunet_nse_interval.rel_value / (double) 2.0) -
+      ((gnunet_nse_interval.rel_value / M_PI) *
+       atan (matching_bits - current_size_estimate));
+}
+
+
+/**
+ * What delay randomization should we apply for a given number of matching bits?
+ *
+ * @param matching_bits number of matching bits
+ * @return random delay to apply
+ */
+static struct GNUNET_TIME_Relative
+get_delay_randomization (uint32_t matching_bits)
+{
+#if USE_RANDOM_DELAYS
+  struct GNUNET_TIME_Relative ret;
+  uint32_t i;
+  double d;
+
+  d = get_matching_bits_delay (matching_bits);
+  i = (uint32_t) (d / (double) (hop_count_max + 1));
+#if DEBUG_NSE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+	      "Randomizing flood using latencies up to %u ms\n",
+	      (unsigned int) i);
+#endif
+  ret.rel_value = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, i + 1);
+  return ret;
+#else
+  return GNUNET_TIME_UNIT_ZERO;
+#endif
+}
+
+
+/**
+ * Get the number of matching bits that the given timestamp has to the given peer ID.
+ *
+ * @param timestamp time to generate key
+ * @param id peer identity to compare with
+ * @return number of matching bits
+ */
+static uint32_t
+get_matching_bits (struct GNUNET_TIME_Absolute timestamp,
+                   const struct GNUNET_PeerIdentity *id)
+{
+  GNUNET_HashCode timestamp_hash;
+
+  GNUNET_CRYPTO_hash (&timestamp.abs_value, sizeof (timestamp.abs_value),
+                      &timestamp_hash);
+  return GNUNET_CRYPTO_hash_matching_bits (&timestamp_hash, &id->hashPubKey);
+}
+
+
+/**
+ * Get the transmission delay that should be applied for a
+ * particular round.
+ *
+ * @param round_offset -1 for the previous round (random delay between 0 and 50ms)
+ *                      0 for the current round (based on our proximity to time key)
+ * @return delay that should be applied
+ */
+static struct GNUNET_TIME_Relative
+get_transmit_delay (int round_offset)
+{
+  struct GNUNET_TIME_Relative ret;
+  struct GNUNET_TIME_Absolute tgt;
+  double dist_delay;
+  uint32_t matching_bits;
+
+  switch (round_offset)
+  {
+  case -1:
+    /* previous round is randomized between 0 and 50 ms */
+#if USE_RANDOM_DELAYS
+    ret.rel_value = GNUNET_CRYPTO_random_u64 (GNUNET_CRYPTO_QUALITY_WEAK, 50);
+#else
+    ret = GNUNET_TIME_UNIT_ZERO;
+#endif
+#if DEBUG_NSE
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Transmitting previous round behind schedule in %llu ms\n",
+                (unsigned long long) ret.rel_value);
+#endif
+    return ret;
+  case 0:
+    /* current round is based on best-known matching_bits */
+    matching_bits =
+        ntohl (size_estimate_messages[estimate_index].matching_bits);
+    dist_delay = get_matching_bits_delay (matching_bits);
+    dist_delay += get_delay_randomization (matching_bits).rel_value;
+    ret.rel_value = (uint64_t) dist_delay;
+#if DEBUG_NSE
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "For round %llu, delay for %u matching bits is %llu ms\n",
+                (unsigned long long) current_timestamp.abs_value,
+                (unsigned int) matching_bits,
+                (unsigned long long) ret.rel_value);
+#endif
+    /* now consider round start time and add delay to it */
+    tgt = GNUNET_TIME_absolute_add (current_timestamp, ret);
+    return GNUNET_TIME_absolute_get_remaining (tgt);
+  }
+  GNUNET_break (0);
+  return GNUNET_TIME_UNIT_FOREVER_REL;
+}
+
+
+/**
+ * Task that triggers a NSE P2P transmission.
+ *
+ * @param cls the 'struct NSEPeerEntry'
+ * @param tc scheduler context
+ */
+static void
+transmit_task_cb (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc);
+
+
+/**
+ * Called when core is ready to send a message we asked for
+ * out to the destination.
+ *
+ * @param cls closure (NULL)
+ * @param size number of bytes available in buf
+ * @param buf where the callee should write the message
+ * @return number of bytes written to buf
+ */
+static size_t
+transmit_ready (void *cls, size_t size, void *buf)
+{
+  struct NSEPeerEntry *peer_entry = cls;
+  unsigned int idx;
+
+  peer_entry->th = NULL;
+  if (buf == NULL)
+  {
+    /* client disconnected */
+    return 0;
+  }
+  GNUNET_assert (size >= sizeof (struct GNUNET_NSE_FloodMessage));
+  idx = estimate_index;
+  if (peer_entry->previous_round == GNUNET_NO)
+  {
+    idx = (idx + HISTORY_SIZE - 1) % HISTORY_SIZE;
+    peer_entry->previous_round = GNUNET_YES;
+    peer_entry->transmit_task =
+        GNUNET_SCHEDULER_add_delayed (get_transmit_delay (0), &transmit_task_cb,
+                                      peer_entry);
+  }
+  if ((ntohl (size_estimate_messages[idx].hop_count) == 0) &&
+      (GNUNET_SCHEDULER_NO_TASK != proof_task))
+  {
+    GNUNET_STATISTICS_update (stats,
+                              "# flood messages not generated (no proof yet)",
+                              1, GNUNET_NO);
+    return 0;
+  }
+  if (ntohs (size_estimate_messages[idx].header.size) == 0)
+  {
+    GNUNET_STATISTICS_update (stats,
+                              "# flood messages not generated (lack of history)",
+                              1, GNUNET_NO);
+    return 0;
+  }
+#if DEBUG_NSE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "In round %llu, sending to `%s' estimate with %u bits\n",
+              (unsigned long long)
+              GNUNET_TIME_absolute_ntoh (size_estimate_messages[idx].
+                                         timestamp).abs_value,
+              GNUNET_i2s (&peer_entry->id),
+              (unsigned int) ntohl (size_estimate_messages[idx].matching_bits));
+#endif
+  if (ntohl (size_estimate_messages[idx].hop_count) == 0)
+    GNUNET_STATISTICS_update (stats, "# flood messages started", 1, GNUNET_NO);
+  GNUNET_STATISTICS_update (stats, "# flood messages transmitted", 1,
+                            GNUNET_NO);
+#if ENABLE_HISTOGRAM
+  peer_entry->transmitted_messages++;
+  peer_entry->last_transmitted_size = 
+      ntohl(size_estimate_messages[idx].matching_bits);
+#endif
+  memcpy (buf, &size_estimate_messages[idx],
+          sizeof (struct GNUNET_NSE_FloodMessage));
+  return sizeof (struct GNUNET_NSE_FloodMessage);
+}
+
+
+/**
+ * Task that triggers a NSE P2P transmission.
+ *
+ * @param cls the 'struct NSEPeerEntry'
+ * @param tc scheduler context
+ */
+static void
+transmit_task_cb (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct NSEPeerEntry *peer_entry = cls;
+
+  peer_entry->transmit_task = GNUNET_SCHEDULER_NO_TASK;
+  GNUNET_assert (NULL == peer_entry->th);
+  peer_entry->th =
+      GNUNET_CORE_notify_transmit_ready (coreAPI, GNUNET_NO, NSE_PRIORITY,
+                                         GNUNET_TIME_UNIT_FOREVER_REL,
+                                         &peer_entry->id,
+                                         sizeof (struct
+                                                 GNUNET_NSE_FloodMessage),
+                                         &transmit_ready, peer_entry);
+}
+
+
+/**
+ * We've sent on our flood message or one that we received which was
+ * validated and closer than ours.  Update the global list of recent
+ * messages and the average.  Also re-broadcast the message to any
+ * clients.
+ */
+static void
+update_network_size_estimate ()
+{
+  struct GNUNET_NSE_ClientMessage em;
+
+  setup_estimate_message (&em);
+  GNUNET_SERVER_notification_context_broadcast (nc, &em.header, GNUNET_YES);
+}
+
+
+/**
+ * Setup a flood message in our history array at the given
+ * slot offset for the given timestamp.
+ *
+ * @param slot index to use
+ * @param ts timestamp to use
+ */
+static void
+setup_flood_message (unsigned int slot, struct GNUNET_TIME_Absolute ts)
+{
+  struct GNUNET_NSE_FloodMessage *fm;
+  uint32_t matching_bits;
+
+  matching_bits = get_matching_bits (ts, &my_identity);
+  fm = &size_estimate_messages[slot];
+  fm->header.size = htons (sizeof (struct GNUNET_NSE_FloodMessage));
+  fm->header.type = htons (GNUNET_MESSAGE_TYPE_NSE_P2P_FLOOD);
+  fm->hop_count = htonl (0);
+  fm->purpose.purpose = htonl (GNUNET_SIGNATURE_PURPOSE_NSE_SEND);
+  fm->purpose.size =
+      htonl (sizeof (struct GNUNET_NSE_FloodMessage) -
+             sizeof (struct GNUNET_MessageHeader) - sizeof (uint32_t) -
+             sizeof (struct GNUNET_CRYPTO_RsaSignature));
+  fm->matching_bits = htonl (matching_bits);
+  fm->timestamp = GNUNET_TIME_absolute_hton (ts);
+  fm->pkey = my_public_key;
+  fm->proof_of_work = my_proof;
+  if (nse_work_required > 0)
+    GNUNET_assert (GNUNET_OK ==
+                   GNUNET_CRYPTO_rsa_sign (my_private_key, &fm->purpose,
+                                           &fm->signature));
+  else
+    memset (&fm->signature, 0, sizeof (fm->signature));
+}
+
+
+/**
+ * Schedule transmission for the given peer for the current round based
+ * on what we know about the desired delay.
+ *
+ * @param cls unused
+ * @param key hash of peer identity
+ * @param value the 'struct NSEPeerEntry'
+ * @return GNUNET_OK (continue to iterate)
+ */
+static int
+schedule_current_round (void *cls, const GNUNET_HashCode * key, void *value)
+{
+  struct NSEPeerEntry *peer_entry = value;
+  struct GNUNET_TIME_Relative delay;
+
+  if (peer_entry->th != NULL)
+  {
+    peer_entry->previous_round = GNUNET_NO;
+    return GNUNET_OK;
+  }
+  if (peer_entry->transmit_task != GNUNET_SCHEDULER_NO_TASK)
+  {
+    GNUNET_SCHEDULER_cancel (peer_entry->transmit_task);
+    peer_entry->previous_round = GNUNET_NO;
+  }
+#if ENABLE_HISTOGRAM
+  if (peer_entry->received_messages > 1)
+    GNUNET_STATISTICS_update(stats, "# extra messages",
+                             peer_entry->received_messages - 1, GNUNET_NO);
+  peer_entry->transmitted_messages = 0;
+  peer_entry->last_transmitted_size = 0;
+  peer_entry->received_messages = 0;
+#endif
+  delay =
+      get_transmit_delay ((peer_entry->previous_round == GNUNET_NO) ? -1 : 0);
+  peer_entry->transmit_task =
+      GNUNET_SCHEDULER_add_delayed (delay, &transmit_task_cb, peer_entry);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Update our flood message to be sent (and our timestamps).
+ *
+ * @param cls unused
+ * @param tc context for this message
+ */
+static void
+update_flood_message (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct GNUNET_TIME_Relative offset;
+  unsigned int i;
+
+  flood_task = GNUNET_SCHEDULER_NO_TASK;
+  if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
+    return;
+  offset = GNUNET_TIME_absolute_get_remaining (next_timestamp);
+  if (0 != offset.rel_value)
+  {
+    /* somehow run early, delay more */
+    flood_task =
+        GNUNET_SCHEDULER_add_delayed (offset, &update_flood_message, NULL);
+    return;
+  }
+  current_timestamp = next_timestamp;
+  next_timestamp =
+      GNUNET_TIME_absolute_add (current_timestamp, gnunet_nse_interval);
+  estimate_index = (estimate_index + 1) % HISTORY_SIZE;
+  if (estimate_count < HISTORY_SIZE)
+    estimate_count++;
+  if (next_timestamp.abs_value ==
+      GNUNET_TIME_absolute_ntoh (next_message.timestamp).abs_value)
+  {
+    /* we received a message for this round way early, use it! */
+    size_estimate_messages[estimate_index] = next_message;
+    size_estimate_messages[estimate_index].hop_count =
+        htonl (1 + ntohl (next_message.hop_count));
+  }
+  else
+    setup_flood_message (estimate_index, current_timestamp);
+  next_message.matching_bits = htonl (0);       /* reset for 'next' round */
+  hop_count_max = 0;
+  for (i = 0; i < HISTORY_SIZE; i++)
+    hop_count_max =
+        GNUNET_MAX (ntohl (size_estimate_messages[i].hop_count), hop_count_max);
+  GNUNET_CONTAINER_multihashmap_iterate (peers, &schedule_current_round, NULL);
+  flood_task =
+      GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_absolute_get_remaining
+                                    (next_timestamp), &update_flood_message,
+                                    NULL);
+}
+
+
+/**
+ * Count the leading zeroes in hash.
+ *
+ * @param hash
+ * @return the number of leading zero bits.
+ */
+static unsigned int
+count_leading_zeroes (const GNUNET_HashCode * hash)
+{
+  unsigned int hash_count;
+
+  hash_count = 0;
+  while ((0 == GNUNET_CRYPTO_hash_get_bit (hash, hash_count)))
+    hash_count++;
+  return hash_count;
+}
+
+
+/**
+ * Check whether the given public key
+ * and integer are a valid proof of work.
+ *
+ * @param pkey the public key
+ * @param val the integer
+ *
+ * @return GNUNET_YES if valid, GNUNET_NO if not
+ */
+static int
+check_proof_of_work (const struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded *pkey,
+                     uint64_t val)
+{
+  char buf[sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded) +
+           sizeof (val)];
+  GNUNET_HashCode result;
+
+  memcpy (buf, &val, sizeof (val));
+  memcpy (&buf[sizeof (val)], pkey,
+          sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded));
+  GNUNET_CRYPTO_hash (buf, sizeof (buf), &result);
+  return (count_leading_zeroes (&result) >=
+          nse_work_required) ? GNUNET_YES : GNUNET_NO;
+}
+
+
+/**
+ * Write our current proof to disk.
+ */
+static void
+write_proof ()
+{
+  char *proof;
+
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_filename (cfg, "NSE", "PROOFFILE", &proof))
+    return;
+  if (sizeof (my_proof) !=
+      GNUNET_DISK_fn_write (proof, &my_proof, sizeof (my_proof),
+                            GNUNET_DISK_PERM_USER_READ |
+                            GNUNET_DISK_PERM_USER_WRITE))
+    GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING, "write", proof);
+  GNUNET_free (proof);
+
+}
+
+
+/**
+ * Find our proof of work.
+ *
+ * @param cls closure (unused)
+ * @param tc task context
+ */
+static void
+find_proof (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+#define ROUND_SIZE 10
+  uint64_t counter;
+  char buf[sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded) +
+           sizeof (uint64_t)];
+  GNUNET_HashCode result;
+  unsigned int i;
+
+  proof_task = GNUNET_SCHEDULER_NO_TASK;
+  memcpy (&buf[sizeof (uint64_t)], &my_public_key,
+          sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded));
+  i = 0;
+  counter = my_proof;
+  while ((counter != UINT64_MAX) && (i < ROUND_SIZE))
+  {
+    memcpy (buf, &counter, sizeof (uint64_t));
+    GNUNET_CRYPTO_hash (buf, sizeof (buf), &result);
+    if (nse_work_required <= count_leading_zeroes (&result))
+    {
+      my_proof = counter;
+#if DEBUG_NSE
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Proof of work found: %llu!\n",
+                  (unsigned long long) GNUNET_ntohll (counter));
+#endif
+      write_proof ();
+      setup_flood_message (estimate_index, current_timestamp);
+      return;
+    }
+    counter++;
+    i++;
+  }
+  if (my_proof / (100 * ROUND_SIZE) < counter / (100 * ROUND_SIZE))
+  {
+#if DEBUG_NSE
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Testing proofs currently at %llu\n",
+                (unsigned long long) counter);
+#endif
+    /* remember progress every 100 rounds */
+    my_proof = counter;
+    write_proof ();
+  }
+  else
+  {
+    my_proof = counter;
+  }
+  proof_task =
+      GNUNET_SCHEDULER_add_delayed_with_priority (proof_find_delay,
+						  GNUNET_SCHEDULER_PRIORITY_IDLE,
+						  &find_proof, NULL);
+}
+
+
+/**
+ * An incoming flood message has been received which claims
+ * to have more bits matching than any we know in this time
+ * period.  Verify the signature and/or proof of work.
+ *
+ * @param incoming_flood the message to verify
+ *
+ * @return GNUNET_YES if the message is verified
+ *         GNUNET_NO if the key/signature don't verify
+ */
+static int
+verify_message_crypto (const struct GNUNET_NSE_FloodMessage *incoming_flood)
+{
+  if (GNUNET_YES !=
+      check_proof_of_work (&incoming_flood->pkey,
+                           incoming_flood->proof_of_work))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO, _("Proof of work invalid: %llu!\n"),
+                (unsigned long long)
+                GNUNET_ntohll (incoming_flood->proof_of_work));
+    GNUNET_break_op (0);
+    return GNUNET_NO;
+  }
+  if ((nse_work_required > 0) &&
+      (GNUNET_OK !=
+       GNUNET_CRYPTO_rsa_verify (GNUNET_SIGNATURE_PURPOSE_NSE_SEND,
+                                 &incoming_flood->purpose,
+                                 &incoming_flood->signature,
+                                 &incoming_flood->pkey)))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_NO;
+  }
+  return GNUNET_YES;
+}
+
+
+/**
+ * Update transmissions for the given peer for the current round based
+ * on updated proximity information.
+ *
+ * @param cls peer entry to exclude from updates
+ * @param key hash of peer identity
+ * @param value the 'struct NSEPeerEntry'
+ * @return GNUNET_OK (continue to iterate)
+ */
+static int
+update_flood_times (void *cls, const GNUNET_HashCode * key, void *value)
+{
+  struct NSEPeerEntry *exclude = cls;
+  struct NSEPeerEntry *peer_entry = value;
+  struct GNUNET_TIME_Relative delay;
+
+  if (peer_entry->th != NULL)
+    return GNUNET_OK;           /* already active */
+  if (peer_entry == exclude)
+    return GNUNET_OK;           /* trigger of the update */
+  if (peer_entry->previous_round == GNUNET_NO)
+  {
+    /* still stuck in previous round, no point to update, check that
+     * we are active here though... */
+    GNUNET_break (peer_entry->transmit_task != GNUNET_SCHEDULER_NO_TASK);
+    return GNUNET_OK;
+  }
+  if (peer_entry->transmit_task != GNUNET_SCHEDULER_NO_TASK)
+  {
+    GNUNET_SCHEDULER_cancel (peer_entry->transmit_task);
+    peer_entry->transmit_task = GNUNET_SCHEDULER_NO_TASK;
+  }
+  delay = get_transmit_delay (0);
+  peer_entry->transmit_task =
+      GNUNET_SCHEDULER_add_delayed (delay, &transmit_task_cb, peer_entry);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Core handler for size estimate flooding messages.
+ *
+ * @param cls closure unused
+ * @param message message
+ * @param peer peer identity this message is from (ignored)
+ * @param atsi performance data (ignored)
+ * @param atsi_count number of records in 'atsi'
+ */
+static int
+handle_p2p_size_estimate (void *cls, const struct GNUNET_PeerIdentity *peer,
+                          const struct GNUNET_MessageHeader *message,
+                          const struct GNUNET_ATS_Information *atsi,
+                          unsigned int atsi_count)
+{
+  const struct GNUNET_NSE_FloodMessage *incoming_flood;
+  struct GNUNET_TIME_Absolute ts;
+  struct NSEPeerEntry *peer_entry;
+  uint32_t matching_bits;
+  unsigned int idx;
+
+#if ENABLE_HISTOGRAM
+  if (NULL != wh)
+    GNUNET_BIO_write_int64 (wh, GNUNET_TIME_absolute_get ().abs_value);
+#endif
+  incoming_flood = (const struct GNUNET_NSE_FloodMessage *) message;
+  GNUNET_STATISTICS_update (stats, "# flood messages received", 1, GNUNET_NO);
+  matching_bits = ntohl (incoming_flood->matching_bits);
+#if DEBUG_NSE
+  {
+    char origin[5];
+    char pred[5];
+    struct GNUNET_PeerIdentity os;
+
+    GNUNET_CRYPTO_hash (&incoming_flood->pkey,
+                        sizeof (struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded),
+                        &os.hashPubKey);
+    GNUNET_snprintf (origin, sizeof (origin), "%s", GNUNET_i2s (&os));
+    GNUNET_snprintf (pred, sizeof (pred), "%s", GNUNET_i2s (peer));
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Flood at %llu from `%s' via `%s' at `%s' with bits %u\n",
+                (unsigned long long)
+                GNUNET_TIME_absolute_ntoh (incoming_flood->timestamp).abs_value,
+                origin, pred, GNUNET_i2s (&my_identity),
+                (unsigned int) matching_bits);
+  }
+#endif
+
+  peer_entry = GNUNET_CONTAINER_multihashmap_get (peers, &peer->hashPubKey);
+  if (NULL == peer_entry)
+  {
+    GNUNET_break (0);
+    return GNUNET_OK;
+  }
+#if ENABLE_HISTOGRAM
+  peer_entry->received_messages++;
+  if (peer_entry->transmitted_messages > 0 && 
+      peer_entry->last_transmitted_size >= matching_bits)
+    GNUNET_STATISTICS_update(stats, "# cross messages", 1, GNUNET_NO);
+#endif
+
+  ts = GNUNET_TIME_absolute_ntoh (incoming_flood->timestamp);
+
+  if (ts.abs_value == current_timestamp.abs_value)
+    idx = estimate_index;
+  else if (ts.abs_value ==
+           current_timestamp.abs_value - gnunet_nse_interval.rel_value)
+    idx = (estimate_index + HISTORY_SIZE - 1) % HISTORY_SIZE;
+  else if (ts.abs_value ==
+           next_timestamp.abs_value - gnunet_nse_interval.rel_value)
+  {
+    if (matching_bits <= ntohl (next_message.matching_bits))
+      return GNUNET_OK;         /* ignore, simply too early/late */
+    if (GNUNET_YES != verify_message_crypto (incoming_flood))
+    {
+      GNUNET_break_op (0);
+      return GNUNET_OK;
+    }
+    next_message = *incoming_flood;
+    return GNUNET_OK;
+  }
+  else
+  {
+    GNUNET_STATISTICS_update (stats,
+                              "# flood messages discarded (clock skew too large)",
+                              1, GNUNET_NO);
+    return GNUNET_OK;
+  }
+  if (0 == (memcmp (peer, &my_identity, sizeof (struct GNUNET_PeerIdentity))))
+  {
+    /* send to self, update our own estimate IF this also comes from us! */
+    if (0 ==
+        memcmp (&incoming_flood->pkey, &my_public_key, sizeof (my_public_key)))
+      update_network_size_estimate ();
+    return GNUNET_OK;
+  }
+  if (matching_bits == ntohl (size_estimate_messages[idx].matching_bits))
+  {
+    /* Cancel transmission in the other direction, as this peer clearly has
+       up-to-date information already. Even if we didn't talk to this peer in
+       the previous round, we should no longer send it stale information as it
+       told us about the current round! */
+    peer_entry->previous_round = GNUNET_YES;
+    if (idx != estimate_index)
+    {
+      /* do not transmit information for the previous round to this peer 
+         anymore (but allow current round) */
+      return GNUNET_OK;
+    }
+    /* got up-to-date information for current round, cancel transmission to
+     * this peer altogether */
+    if (GNUNET_SCHEDULER_NO_TASK != peer_entry->transmit_task)
+    {
+      GNUNET_SCHEDULER_cancel (peer_entry->transmit_task);
+      peer_entry->transmit_task = GNUNET_SCHEDULER_NO_TASK;
+    }
+    if (peer_entry->th != NULL)
+    {
+      GNUNET_CORE_notify_transmit_ready_cancel (peer_entry->th);
+      peer_entry->th = NULL;
+    }
+    return GNUNET_OK;
+  }
+  if (matching_bits < ntohl (size_estimate_messages[idx].matching_bits))
+  {
+    if ((idx < estimate_index) && (peer_entry->previous_round == GNUNET_YES))
+      peer_entry->previous_round = GNUNET_NO;
+    /* push back our result now, that peer is spreading bad information... */
+    if (NULL == peer_entry->th)
+    {
+      if (peer_entry->transmit_task != GNUNET_SCHEDULER_NO_TASK)
+        GNUNET_SCHEDULER_cancel (peer_entry->transmit_task);
+      peer_entry->transmit_task =
+          GNUNET_SCHEDULER_add_now (&transmit_task_cb, peer_entry);
+    }
+    /* Not closer than our most recent message, no need to do work here */
+    GNUNET_STATISTICS_update (stats,
+                              "# flood messages ignored (had closer already)",
+                              1, GNUNET_NO);
+    return GNUNET_OK;
+  }
+  if (GNUNET_YES != verify_message_crypto (incoming_flood))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_OK;
+  }
+  GNUNET_assert (matching_bits >
+                 ntohl (size_estimate_messages[idx].matching_bits));
+  /* cancel transmission from us to this peer for this round */
+  if (idx == estimate_index)
+  {
+      /* cancel any activity for current round */
+      if (peer_entry->transmit_task != GNUNET_SCHEDULER_NO_TASK)
+      {
+        GNUNET_SCHEDULER_cancel (peer_entry->transmit_task);
+        peer_entry->transmit_task = GNUNET_SCHEDULER_NO_TASK;
+      }
+      if (peer_entry->th != NULL)
+      {
+        GNUNET_CORE_notify_transmit_ready_cancel (peer_entry->th);
+        peer_entry->th = NULL;
+      }
+  }
+  else
+  {
+    /* cancel previous round only */
+    peer_entry->previous_round = GNUNET_YES;
+  }
+  size_estimate_messages[idx] = *incoming_flood;
+  size_estimate_messages[idx].hop_count =
+      htonl (ntohl (incoming_flood->hop_count) + 1);
+  hop_count_max =
+      GNUNET_MAX (ntohl (incoming_flood->hop_count) + 1, hop_count_max);
+  GNUNET_STATISTICS_set (stats,
+			 "# estimated network diameter",
+			 hop_count_max, GNUNET_NO);
+
+  /* have a new, better size estimate, inform clients */
+  update_network_size_estimate ();
+
+  /* flood to rest */
+  GNUNET_CONTAINER_multihashmap_iterate (peers, &update_flood_times,
+                                         peer_entry);
+  return GNUNET_OK;
+}
+
+
+
+/**
+ * Method called whenever a peer connects.
+ *
+ * @param cls closure
+ * @param peer peer identity this notification is about
+ * @param atsi performance data
+ * @param atsi_count number of records in 'atsi'
+ */
+static void
+handle_core_connect (void *cls, const struct GNUNET_PeerIdentity *peer,
+                     const struct GNUNET_ATS_Information *atsi,
+                     unsigned int atsi_count)
+{
+  struct NSEPeerEntry *peer_entry;
+
+#if DEBUG_NSE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Peer `%s' connected to us\n",
+              GNUNET_i2s (peer));
+#endif
+  peer_entry = GNUNET_malloc (sizeof (struct NSEPeerEntry));
+  peer_entry->id = *peer;
+  GNUNET_assert (GNUNET_OK ==
+                 GNUNET_CONTAINER_multihashmap_put (peers, &peer->hashPubKey,
+                                                    peer_entry,
+                                                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
+  peer_entry->transmit_task =
+      GNUNET_SCHEDULER_add_delayed (get_transmit_delay (-1), &transmit_task_cb,
+                                    peer_entry);
+  GNUNET_STATISTICS_update (stats, "# peers", 1, GNUNET_NO);
+}
+
+
+/**
+ * Method called whenever a peer disconnects.
+ *
+ * @param cls closure
+ * @param peer peer identity this notification is about
+ */
+static void
+handle_core_disconnect (void *cls, const struct GNUNET_PeerIdentity *peer)
+{
+  struct NSEPeerEntry *pos;
+
+#if DEBUG_NSE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Peer `%s' disconnected from us\n",
+              GNUNET_i2s (peer));
+#endif
+  pos = GNUNET_CONTAINER_multihashmap_get (peers, &peer->hashPubKey);
+  if (NULL == pos)
+  {
+    GNUNET_break (0);
+    return;
+  }
+  GNUNET_assert (GNUNET_YES ==
+                 GNUNET_CONTAINER_multihashmap_remove (peers, &peer->hashPubKey,
+                                                       pos));
+  if (pos->transmit_task != GNUNET_SCHEDULER_NO_TASK)
+    GNUNET_SCHEDULER_cancel (pos->transmit_task);
+  if (pos->th != NULL)
+  {
+    GNUNET_CORE_notify_transmit_ready_cancel (pos->th);
+    pos->th = NULL;
+  }
+  GNUNET_free (pos);
+  GNUNET_STATISTICS_update (stats, "# peers", -1, GNUNET_NO);
+}
+
+
+/**
+ * Task run during shutdown.
+ *
+ * @param cls unused
+ * @param tc unused
+ */
+static void
+shutdown_task (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  if (flood_task != GNUNET_SCHEDULER_NO_TASK)
+  {
+    GNUNET_SCHEDULER_cancel (flood_task);
+    flood_task = GNUNET_SCHEDULER_NO_TASK;
+  }
+  if (proof_task != GNUNET_SCHEDULER_NO_TASK)
+  {
+    GNUNET_SCHEDULER_cancel (proof_task);
+    proof_task = GNUNET_SCHEDULER_NO_TASK;
+    write_proof ();             /* remember progress */
+  }
+  if (nc != NULL)
+  {
+    GNUNET_SERVER_notification_context_destroy (nc);
+    nc = NULL;
+  }
+  if (coreAPI != NULL)
+  {
+    GNUNET_CORE_disconnect (coreAPI);
+    coreAPI = NULL;
+  }
+  if (stats != NULL)
+  {
+    GNUNET_STATISTICS_destroy (stats, GNUNET_NO);
+    stats = NULL;
+  }
+  if (peers != NULL)
+  {
+    GNUNET_CONTAINER_multihashmap_destroy (peers);
+    peers = NULL;
+  }
+  if (my_private_key != NULL)
+  {
+    GNUNET_CRYPTO_rsa_key_free (my_private_key);
+    my_private_key = NULL;
+  }
+#if ENABLE_HISTOGRAM
+  if (wh != NULL)
+  {
+    GNUNET_BIO_write_close (wh);
+    wh = NULL;
+  }
+#endif
+}
+
+
+/**
+ * Called on core init/fail.
+ *
+ * @param cls service closure
+ * @param server handle to the server for this service
+ * @param identity the public identity of this peer
+ */
+static void
+core_init (void *cls, struct GNUNET_CORE_Handle *server,
+           const struct GNUNET_PeerIdentity *identity)
+{
+  struct GNUNET_TIME_Absolute now;
+  struct GNUNET_TIME_Absolute prev_time;
+
+  if (server == NULL)
+  {
+#if DEBUG_NSE
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Connection to core FAILED!\n");
+#endif
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  GNUNET_assert (0 ==
+                 memcmp (&my_identity, identity,
+                         sizeof (struct GNUNET_PeerIdentity)));
+  now = GNUNET_TIME_absolute_get ();
+  current_timestamp.abs_value =
+      (now.abs_value / gnunet_nse_interval.rel_value) *
+      gnunet_nse_interval.rel_value;
+  next_timestamp =
+      GNUNET_TIME_absolute_add (current_timestamp, gnunet_nse_interval);
+  estimate_index = HISTORY_SIZE - 1;
+  estimate_count = 0;
+  if (GNUNET_YES == check_proof_of_work (&my_public_key, my_proof))
+  {
+    prev_time.abs_value =
+        current_timestamp.abs_value - gnunet_nse_interval.rel_value;
+    setup_flood_message (estimate_index, prev_time);
+    estimate_count++;
+  }
+  flood_task =
+      GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_absolute_get_remaining
+                                    (next_timestamp), &update_flood_message,
+                                    NULL);
+}
+
+
+/**
+ * Handle network size estimate clients.
+ *
+ * @param cls closure
+ * @param server the initialized server
+ * @param c configuration to use
+ */
+static void
+run (void *cls, struct GNUNET_SERVER_Handle *server,
+     const struct GNUNET_CONFIGURATION_Handle *c)
+{
+  char *keyfile;
+  char *proof;
+
+  static const struct GNUNET_SERVER_MessageHandler handlers[] = {
+    {&handle_start_message, NULL, GNUNET_MESSAGE_TYPE_NSE_START,
+     sizeof (struct GNUNET_MessageHeader)},
+    {NULL, NULL, 0, 0}
+  };
+  static const struct GNUNET_CORE_MessageHandler core_handlers[] = {
+    {&handle_p2p_size_estimate, GNUNET_MESSAGE_TYPE_NSE_P2P_FLOOD,
+     sizeof (struct GNUNET_NSE_FloodMessage)},
+    {NULL, 0, 0}
+  };
+  cfg = c;
+
+  if ((GNUNET_OK !=
+       GNUNET_CONFIGURATION_get_value_time (cfg, "NSE", "INTERVAL",
+                                            &gnunet_nse_interval)) ||
+      (GNUNET_OK !=
+       GNUNET_CONFIGURATION_get_value_time (cfg, "NSE", "WORKDELAY",
+                                            &proof_find_delay)) ||
+      (GNUNET_OK !=
+       GNUNET_CONFIGURATION_get_value_number (cfg, "NSE", "WORKBITS",
+                                              &nse_work_required)))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                _
+                ("NSE service is lacking key configuration settings.  Exiting.\n"));
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  if (nse_work_required >= sizeof (GNUNET_HashCode) * 8)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                _("Invalid work requirement for NSE service. Exiting.\n"));
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+
+
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_filename (cfg, "GNUNETD", "HOSTKEY",
+                                               &keyfile))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                _
+                ("NSE service is lacking key configuration settings.  Exiting.\n"));
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  my_private_key = GNUNET_CRYPTO_rsa_key_create_from_file (keyfile);
+  GNUNET_free (keyfile);
+  if (my_private_key == NULL)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                _("NSE service could not access hostkey.  Exiting.\n"));
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  GNUNET_CRYPTO_rsa_key_get_public (my_private_key, &my_public_key);
+  GNUNET_CRYPTO_hash (&my_public_key, sizeof (my_public_key),
+                      &my_identity.hashPubKey);
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_filename (cfg, "NSE", "PROOFFILE", &proof))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                _
+                ("NSE service is lacking key configuration settings.  Exiting.\n"));
+    if (my_private_key != NULL)
+    {
+      GNUNET_CRYPTO_rsa_key_free (my_private_key);
+      my_private_key = NULL;
+    }
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  if ((GNUNET_YES != GNUNET_DISK_file_test (proof)) ||
+      (sizeof (my_proof) !=
+       GNUNET_DISK_fn_read (proof, &my_proof, sizeof (my_proof))))
+    my_proof = 0;
+  GNUNET_free (proof);
+  proof_task =
+      GNUNET_SCHEDULER_add_with_priority (GNUNET_SCHEDULER_PRIORITY_IDLE,
+                                          &find_proof, NULL);
+
+  peers = GNUNET_CONTAINER_multihashmap_create (128);
+  GNUNET_SERVER_add_handlers (server, handlers);
+  nc = GNUNET_SERVER_notification_context_create (server, 1);
+  /* Connect to core service and register core handlers */
+  coreAPI = GNUNET_CORE_connect (cfg,   /* Main configuration */
+                                 1, NULL,       /* Closure passed to functions */
+                                 &core_init,    /* Call core_init once connected */
+                                 &handle_core_connect,  /* Handle connects */
+                                 &handle_core_disconnect,       /* Handle disconnects */
+                                 NULL,  /* Don't want notified about all incoming messages */
+                                 GNUNET_NO,     /* For header only inbound notification */
+                                 NULL,  /* Don't want notified about all outbound messages */
+                                 GNUNET_NO,     /* For header only outbound notification */
+                                 core_handlers);        /* Register these handlers */
+  GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL, &shutdown_task,
+                                NULL);
+#if ENABLE_HISTOGRAM
+  if (GNUNET_OK ==
+      GNUNET_CONFIGURATION_get_value_filename (cfg, "NSE", "HISTOGRAM", &proof))
+  {
+    wh = GNUNET_BIO_write_open (proof);
+    GNUNET_free (proof);
+  }
+#endif
+  if (coreAPI == NULL)
+  {
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  stats = GNUNET_STATISTICS_create ("nse", cfg);
+}
+
+
+/**
+ * The main function for the statistics service.
+ *
+ * @param argc number of arguments from the command line
+ * @param argv command line arguments
+ * @return 0 ok, 1 on error
+ */
+int
+main (int argc, char *const *argv)
+{
+  return (GNUNET_OK ==
+          GNUNET_SERVICE_run (argc, argv, "nse", GNUNET_SERVICE_OPTION_NONE,
+                              &run, NULL)) ? 0 : 1;
+}
+
+/* end of gnunet-service-nse.c */