aboutsummaryrefslogtreecommitdiffstats
path: root/whisper/whisperv6/whisper.go
blob: 4e2d6abb0da35a16c9719d09dff65f00636c5d2d (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package whisperv6

import (
    "bytes"
    "crypto/ecdsa"
    "crypto/sha256"
    "fmt"
    "math"
    "runtime"
    "sync"
    "time"

    mapset "github.com/deckarep/golang-set"
    "github.com/dexon-foundation/dexon/common"
    "github.com/dexon-foundation/dexon/crypto"
    "github.com/dexon-foundation/dexon/log"
    "github.com/dexon-foundation/dexon/p2p"
    "github.com/dexon-foundation/dexon/rlp"
    "github.com/dexon-foundation/dexon/rpc"
    "github.com/syndtr/goleveldb/leveldb/errors"
    "golang.org/x/crypto/pbkdf2"
    "golang.org/x/sync/syncmap"
)

// Statistics holds several message-related counter for analytics
// purposes.
type Statistics struct {
    messagesCleared      int
    memoryCleared        int
    memoryUsed           int
    cycles               int
    totalMessagesCleared int
}

const (
    maxMsgSizeIdx                            = iota // Maximal message length allowed by the whisper node
    overflowIdx                                     // Indicator of message queue overflow
    minPowIdx                                       // Minimal PoW required by the whisper node
    minPowToleranceIdx                              // Minimal PoW tolerated by the whisper node for a limited time
    bloomFilterIdx                                  // Bloom filter for topics of interest for this node
    bloomFilterToleranceIdx                         // Bloom filter tolerated by the whisper node for a limited time
    lightClientModeIdx                              // Light client mode. (does not forward any messages)
    restrictConnectionBetweenLightClientsIdx        // Restrict connection between two light clients
)

// Whisper represents a dark communication interface through the Ethereum
// network, using its very own P2P communication layer.
type Whisper struct {
    protocol p2p.Protocol // Protocol description and parameters
    filters  *Filters     // Message filters installed with Subscribe function

    privateKeys map[string]*ecdsa.PrivateKey // Private key storage
    symKeys     map[string][]byte            // Symmetric key storage
    keyMu       sync.RWMutex                 // Mutex associated with key storages

    poolMu      sync.RWMutex              // Mutex to sync the message and expiration pools
    envelopes   map[common.Hash]*Envelope // Pool of envelopes currently tracked by this node
    expirations map[uint32]mapset.Set     // Message expiration pool

    peerMu sync.RWMutex       // Mutex to sync the active peer set
    peers  map[*Peer]struct{} // Set of currently active peers

    messageQueue chan *Envelope // Message queue for normal whisper messages
    p2pMsgQueue  chan *Envelope // Message queue for peer-to-peer messages (not to be forwarded any further)
    quit         chan struct{}  // Channel used for graceful exit

    settings syncmap.Map // holds configuration settings that can be dynamically changed

    syncAllowance int // maximum time in seconds allowed to process the whisper-related messages

    statsMu sync.Mutex // guard stats
    stats   Statistics // Statistics of whisper node

    mailServer MailServer // MailServer interface
}

// New creates a Whisper client ready to communicate through the Ethereum P2P network.
func New(cfg *Config) *Whisper {
    if cfg == nil {
        cfg = &DefaultConfig
    }

    whisper := &Whisper{
        privateKeys:   make(map[string]*ecdsa.PrivateKey),
        symKeys:       make(map[string][]byte),
        envelopes:     make(map[common.Hash]*Envelope),
        expirations:   make(map[uint32]mapset.Set),
        peers:         make(map[*Peer]struct{}),
        messageQueue:  make(chan *Envelope, messageQueueLimit),
        p2pMsgQueue:   make(chan *Envelope, messageQueueLimit),
        quit:          make(chan struct{}),
        syncAllowance: DefaultSyncAllowance,
    }

    whisper.filters = NewFilters(whisper)

    whisper.settings.Store(minPowIdx, cfg.MinimumAcceptedPOW)
    whisper.settings.Store(maxMsgSizeIdx, cfg.MaxMessageSize)
    whisper.settings.Store(overflowIdx, false)
    whisper.settings.Store(restrictConnectionBetweenLightClientsIdx, cfg.RestrictConnectionBetweenLightClients)

    // p2p whisper sub protocol handler
    whisper.protocol = p2p.Protocol{
        Name:    ProtocolName,
        Version: uint(ProtocolVersion),
        Length:  NumberOfMessageCodes,
        Run:     whisper.HandlePeer,
        NodeInfo: func() interface{} {
            return map[string]interface{}{
                "version":        ProtocolVersionStr,
                "maxMessageSize": whisper.MaxMessageSize(),
                "minimumPoW":     whisper.MinPow(),
            }
        },
    }

    return whisper
}

// MinPow returns the PoW value required by this node.
func (whisper *Whisper) MinPow() float64 {
    val, exist := whisper.settings.Load(minPowIdx)
    if !exist || val == nil {
        return DefaultMinimumPoW
    }
    v, ok := val.(float64)
    if !ok {
        log.Error("Error loading minPowIdx, using default")
        return DefaultMinimumPoW
    }
    return v
}

// MinPowTolerance returns the value of minimum PoW which is tolerated for a limited
// time after PoW was changed. If sufficient time have elapsed or no change of PoW
// have ever occurred, the return value will be the same as return value of MinPow().
func (whisper *Whisper) MinPowTolerance() float64 {
    val, exist := whisper.settings.Load(minPowToleranceIdx)
    if !exist || val == nil {
        return DefaultMinimumPoW
    }
    return val.(float64)
}

// BloomFilter returns the aggregated bloom filter for all the topics of interest.
// The nodes are required to send only messages that match the advertised bloom filter.
// If a message does not match the bloom, it will tantamount to spam, and the peer will
// be disconnected.
func (whisper *Whisper) BloomFilter() []byte {
    val, exist := whisper.settings.Load(bloomFilterIdx)
    if !exist || val == nil {
        return nil
    }
    return val.([]byte)
}

// BloomFilterTolerance returns the bloom filter which is tolerated for a limited
// time after new bloom was advertised to the peers. If sufficient time have elapsed
// or no change of bloom filter have ever occurred, the return value will be the same
// as return value of BloomFilter().
func (whisper *Whisper) BloomFilterTolerance() []byte {
    val, exist := whisper.settings.Load(bloomFilterToleranceIdx)
    if !exist || val == nil {
        return nil
    }
    return val.([]byte)
}

// MaxMessageSize returns the maximum accepted message size.
func (whisper *Whisper) MaxMessageSize() uint32 {
    val, _ := whisper.settings.Load(maxMsgSizeIdx)
    return val.(uint32)
}

// Overflow returns an indication if the message queue is full.
func (whisper *Whisper) Overflow() bool {
    val, _ := whisper.settings.Load(overflowIdx)
    return val.(bool)
}

// APIs returns the RPC descriptors the Whisper implementation offers
func (whisper *Whisper) APIs() []rpc.API {
    return []rpc.API{
        {
            Namespace: ProtocolName,
            Version:   ProtocolVersionStr,
            Service:   NewPublicWhisperAPI(whisper),
            Public:    true,
        },
    }
}

// RegisterServer registers MailServer interface.
// MailServer will process all the incoming messages with p2pRequestCode.
func (whisper *Whisper) RegisterServer(server MailServer) {
    whisper.mailServer = server
}

// Protocols returns the whisper sub-protocols ran by this particular client.
func (whisper *Whisper) Protocols() []p2p.Protocol {
    return []p2p.Protocol{whisper.protocol}
}

// Version returns the whisper sub-protocols version number.
func (whisper *Whisper) Version() uint {
    return whisper.protocol.Version
}

// SetMaxMessageSize sets the maximal message size allowed by this node
func (whisper *Whisper) SetMaxMessageSize(size uint32) error {
    if size > MaxMessageSize {
        return fmt.Errorf("message size too large [%d>%d]", size, MaxMessageSize)
    }
    whisper.settings.Store(maxMsgSizeIdx, size)
    return nil
}

// SetBloomFilter sets the new bloom filter
func (whisper *Whisper) SetBloomFilter(bloom []byte) error {
    if len(bloom) != BloomFilterSize {
        return fmt.Errorf("invalid bloom filter size: %d", len(bloom))
    }

    b := make([]byte, BloomFilterSize)
    copy(b, bloom)

    whisper.settings.Store(bloomFilterIdx, b)
    whisper.notifyPeersAboutBloomFilterChange(b)

    go func() {
        // allow some time before all the peers have processed the notification
        time.Sleep(time.Duration(whisper.syncAllowance) * time.Second)
        whisper.settings.Store(bloomFilterToleranceIdx, b)
    }()

    return nil
}

// SetMinimumPoW sets the minimal PoW required by this node
func (whisper *Whisper) SetMinimumPoW(val float64) error {
    if val < 0.0 {
        return fmt.Errorf("invalid PoW: %f", val)
    }

    whisper.settings.Store(minPowIdx, val)
    whisper.notifyPeersAboutPowRequirementChange(val)

    go func() {
        // allow some time before all the peers have processed the notification
        time.Sleep(time.Duration(whisper.syncAllowance) * time.Second)
        whisper.settings.Store(minPowToleranceIdx, val)
    }()

    return nil
}

// SetMinimumPowTest sets the minimal PoW in test environment
func (whisper *Whisper) SetMinimumPowTest(val float64) {
    whisper.settings.Store(minPowIdx, val)
    whisper.notifyPeersAboutPowRequirementChange(val)
    whisper.settings.Store(minPowToleranceIdx, val)
}

//SetLightClientMode makes node light client (does not forward any messages)
func (whisper *Whisper) SetLightClientMode(v bool) {
    whisper.settings.Store(lightClientModeIdx, v)
}

//LightClientMode indicates is this node is light client (does not forward any messages)
func (whisper *Whisper) LightClientMode() bool {
    val, exist := whisper.settings.Load(lightClientModeIdx)
    if !exist || val == nil {
        return false
    }
    v, ok := val.(bool)
    return v && ok
}

//LightClientModeConnectionRestricted indicates that connection to light client in light client mode not allowed
func (whisper *Whisper) LightClientModeConnectionRestricted() bool {
    val, exist := whisper.settings.Load(restrictConnectionBetweenLightClientsIdx)
    if !exist || val == nil {
        return false
    }
    v, ok := val.(bool)
    return v && ok
}

func (whisper *Whisper) notifyPeersAboutPowRequirementChange(pow float64) {
    arr := whisper.getPeers()
    for _, p := range arr {
        err := p.notifyAboutPowRequirementChange(pow)
        if err != nil {
            // allow one retry
            err = p.notifyAboutPowRequirementChange(pow)
        }
        if err != nil {
            log.Warn("failed to notify peer about new pow requirement", "peer", p.ID(), "error", err)
        }
    }
}

func (whisper *Whisper) notifyPeersAboutBloomFilterChange(bloom []byte) {
    arr := whisper.getPeers()
    for _, p := range arr {
        err := p.notifyAboutBloomFilterChange(bloom)
        if err != nil {
            // allow one retry
            err = p.notifyAboutBloomFilterChange(bloom)
        }
        if err != nil {
            log.Warn("failed to notify peer about new bloom filter", "peer", p.ID(), "error", err)
        }
    }
}

func (whisper *Whisper) getPeers() []*Peer {
    arr := make([]*Peer, len(whisper.peers))
    i := 0
    whisper.peerMu.Lock()
    for p := range whisper.peers {
        arr[i] = p
        i++
    }
    whisper.peerMu.Unlock()
    return arr
}

// getPeer retrieves peer by ID
func (whisper *Whisper) getPeer(peerID []byte) (*Peer, error) {
    whisper.peerMu.Lock()
    defer whisper.peerMu.Unlock()
    for p := range whisper.peers {
        id := p.peer.ID()
        if bytes.Equal(peerID, id[:]) {
            return p, nil
        }
    }
    return nil, fmt.Errorf("Could not find peer with ID: %x", peerID)
}

// AllowP2PMessagesFromPeer marks specific peer trusted,
// which will allow it to send historic (expired) messages.
func (whisper *Whisper) AllowP2PMessagesFromPeer(peerID []byte) error {
    p, err := whisper.getPeer(peerID)
    if err != nil {
        return err
    }
    p.trusted = true
    return nil
}

// RequestHistoricMessages sends a message with p2pRequestCode to a specific peer,
// which is known to implement MailServer interface, and is supposed to process this
// request and respond with a number of peer-to-peer messages (possibly expired),
// which are not supposed to be forwarded any further.
// The whisper protocol is agnostic of the format and contents of envelope.
func (whisper *Whisper) RequestHistoricMessages(peerID []byte, envelope *Envelope) error {
    p, err := whisper.getPeer(peerID)
    if err != nil {
        return err
    }
    p.trusted = true
    return p2p.Send(p.ws, p2pRequestCode, envelope)
}

// SendP2PMessage sends a peer-to-peer message to a specific peer.
func (whisper *Whisper) SendP2PMessage(peerID []byte, envelope *Envelope) error {
    p, err := whisper.getPeer(peerID)
    if err != nil {
        return err
    }
    return whisper.SendP2PDirect(p, envelope)
}

// SendP2PDirect sends a peer-to-peer message to a specific peer.
func (whisper *Whisper) SendP2PDirect(peer *Peer, envelope *Envelope) error {
    return p2p.Send(peer.ws, p2pMessageCode, envelope)
}

// NewKeyPair generates a new cryptographic identity for the client, and injects
// it into the known identities for message decryption. Returns ID of the new key pair.
func (whisper *Whisper) NewKeyPair() (string, error) {
    key, err := crypto.GenerateKey()
    if err != nil || !validatePrivateKey(key) {
        key, err = crypto.GenerateKey() // retry once
    }
    if err != nil {
        return "", err
    }
    if !validatePrivateKey(key) {
        return "", fmt.Errorf("failed to generate valid key")
    }

    id, err := GenerateRandomID()
    if err != nil {
        return "", fmt.Errorf("failed to generate ID: %s", err)
    }

    whisper.keyMu.Lock()
    defer whisper.keyMu.Unlock()

    if whisper.privateKeys[id] != nil {
        return "", fmt.Errorf("failed to generate unique ID")
    }
    whisper.privateKeys[id] = key
    return id, nil
}

// DeleteKeyPair deletes the specified key if it exists.
func (whisper *Whisper) DeleteKeyPair(key string) bool {
    whisper.keyMu.Lock()
    defer whisper.keyMu.Unlock()

    if whisper.privateKeys[key] != nil {
        delete(whisper.privateKeys, key)
        return true
    }
    return false
}

// AddKeyPair imports a asymmetric private key and returns it identifier.
func (whisper *Whisper) AddKeyPair(key *ecdsa.PrivateKey) (string, error) {
    id, err := GenerateRandomID()
    if err != nil {
        return "", fmt.Errorf("failed to generate ID: %s", err)
    }

    whisper.keyMu.Lock()
    whisper.privateKeys[id] = key
    whisper.keyMu.Unlock()

    return id, nil
}

// HasKeyPair checks if the whisper node is configured with the private key
// of the specified public pair.
func (whisper *Whisper) HasKeyPair(id string) bool {
    whisper.keyMu.RLock()
    defer whisper.keyMu.RUnlock()
    return whisper.privateKeys[id] != nil
}

// GetPrivateKey retrieves the private key of the specified identity.
func (whisper *Whisper) GetPrivateKey(id string) (*ecdsa.PrivateKey, error) {
    whisper.keyMu.RLock()
    defer whisper.keyMu.RUnlock()
    key := whisper.privateKeys[id]
    if key == nil {
        return nil, fmt.Errorf("invalid id")
    }
    return key, nil
}

// GenerateSymKey generates a random symmetric key and stores it under id,
// which is then returned. Will be used in the future for session key exchange.
func (whisper *Whisper) GenerateSymKey() (string, error) {
    key, err := generateSecureRandomData(aesKeyLength)
    if err != nil {
        return "", err
    } else if !validateDataIntegrity(key, aesKeyLength) {
        return "", fmt.Errorf("error in GenerateSymKey: crypto/rand failed to generate random data")
    }

    id, err := GenerateRandomID()
    if err != nil {
        return "", fmt.Errorf("failed to generate ID: %s", err)
    }

    whisper.keyMu.Lock()
    defer whisper.keyMu.Unlock()

    if whisper.symKeys[id] != nil {
        return "", fmt.Errorf("failed to generate unique ID")
    }
    whisper.symKeys[id] = key
    return id, nil
}

// AddSymKeyDirect stores the key, and returns its id.
func (whisper *Whisper) AddSymKeyDirect(key []byte) (string, error) {
    if len(key) != aesKeyLength {
        return "", fmt.Errorf("wrong key size: %d", len(key))
    }

    id, err := GenerateRandomID()
    if err != nil {
        return "", fmt.Errorf("failed to generate ID: %s", err)
    }

    whisper.keyMu.Lock()
    defer whisper.keyMu.Unlock()

    if whisper.symKeys[id] != nil {
        return "", fmt.Errorf("failed to generate unique ID")
    }
    whisper.symKeys[id] = key
    return id, nil
}

// AddSymKeyFromPassword generates the key from password, stores it, and returns its id.
func (whisper *Whisper) AddSymKeyFromPassword(password string) (string, error) {
    id, err := GenerateRandomID()
    if err != nil {
        return "", fmt.Errorf("failed to generate ID: %s", err)
    }
    if whisper.HasSymKey(id) {
        return "", fmt.Errorf("failed to generate unique ID")
    }

    // kdf should run no less than 0.1 seconds on an average computer,
    // because it's an once in a session experience
    derived := pbkdf2.Key([]byte(password), nil, 65356, aesKeyLength, sha256.New)
    if err != nil {
        return "", err
    }

    whisper.keyMu.Lock()
    defer whisper.keyMu.Unlock()

    // double check is necessary, because deriveKeyMaterial() is very slow
    if whisper.symKeys[id] != nil {
        return "", fmt.Errorf("critical error: failed to generate unique ID")
    }
    whisper.symKeys[id] = derived
    return id, nil
}

// HasSymKey returns true if there is a key associated with the given id.
// Otherwise returns false.
func (whisper *Whisper) HasSymKey(id string) bool {
    whisper.keyMu.RLock()
    defer whisper.keyMu.RUnlock()
    return whisper.symKeys[id] != nil
}

// DeleteSymKey deletes the key associated with the name string if it exists.
func (whisper *Whisper) DeleteSymKey(id string) bool {
    whisper.keyMu.Lock()
    defer whisper.keyMu.Unlock()
    if whisper.symKeys[id] != nil {
        delete(whisper.symKeys, id)
        return true
    }
    return false
}

// GetSymKey returns the symmetric key associated with the given id.
func (whisper *Whisper) GetSymKey(id string) ([]byte, error) {
    whisper.keyMu.RLock()
    defer whisper.keyMu.RUnlock()
    if whisper.symKeys[id] != nil {
        return whisper.symKeys[id], nil
    }
    return nil, fmt.Errorf("non-existent key ID")
}

// Subscribe installs a new message handler used for filtering, decrypting
// and subsequent storing of incoming messages.
func (whisper *Whisper) Subscribe(f *Filter) (string, error) {
    s, err := whisper.filters.Install(f)
    if err == nil {
        whisper.updateBloomFilter(f)
    }
    return s, err
}

// updateBloomFilter recalculates the new value of bloom filter,
// and informs the peers if necessary.
func (whisper *Whisper) updateBloomFilter(f *Filter) {
    aggregate := make([]byte, BloomFilterSize)
    for _, t := range f.Topics {
        top := BytesToTopic(t)
        b := TopicToBloom(top)
        aggregate = addBloom(aggregate, b)
    }

    if !BloomFilterMatch(whisper.BloomFilter(), aggregate) {
        // existing bloom filter must be updated
        aggregate = addBloom(whisper.BloomFilter(), aggregate)
        whisper.SetBloomFilter(aggregate)
    }
}

// GetFilter returns the filter by id.
func (whisper *Whisper) GetFilter(id string) *Filter {
    return whisper.filters.Get(id)
}

// Unsubscribe removes an installed message handler.
func (whisper *Whisper) Unsubscribe(id string) error {
    ok := whisper.filters.Uninstall(id)
    if !ok {
        return fmt.Errorf("Unsubscribe: Invalid ID")
    }
    return nil
}

// Send injects a message into the whisper send queue, to be distributed in the
// network in the coming cycles.
func (whisper *Whisper) Send(envelope *Envelope) error {
    ok, err := whisper.add(envelope, false)
    if err == nil && !ok {
        return fmt.Errorf("failed to add envelope")
    }
    return err
}

// Start implements node.Service, starting the background data propagation thread
// of the Whisper protocol.
func (whisper *Whisper) Start(*p2p.Server) error {
    log.Info("started whisper v." + ProtocolVersionStr)
    go whisper.update()

    numCPU := runtime.NumCPU()
    for i := 0; i < numCPU; i++ {
        go whisper.processQueue()
    }

    return nil
}

// Stop implements node.Service, stopping the background data propagation thread
// of the Whisper protocol.
func (whisper *Whisper) Stop() error {
    close(whisper.quit)
    log.Info("whisper stopped")
    return nil
}

// HandlePeer is called by the underlying P2P layer when the whisper sub-protocol
// connection is negotiated.
func (whisper *Whisper) HandlePeer(peer *p2p.Peer, rw p2p.MsgReadWriter) error {
    // Create the new peer and start tracking it
    whisperPeer := newPeer(whisper, peer, rw)

    whisper.peerMu.Lock()
    whisper.peers[whisperPeer] = struct{}{}
    whisper.peerMu.Unlock()

    defer func() {
        whisper.peerMu.Lock()
        delete(whisper.peers, whisperPeer)
        whisper.peerMu.Unlock()
    }()

    // Run the peer handshake and state updates
    if err := whisperPeer.handshake(); err != nil {
        return err
    }
    whisperPeer.start()
    defer whisperPeer.stop()

    return whisper.runMessageLoop(whisperPeer, rw)
}

// runMessageLoop reads and processes inbound messages directly to merge into client-global state.
func (whisper *Whisper) runMessageLoop(p *Peer, rw p2p.MsgReadWriter) error {
    for {
        // fetch the next packet
        packet, err := rw.ReadMsg()
        if err != nil {
            log.Info("message loop", "peer", p.peer.ID(), "err", err)
            return err
        }
        if packet.Size > whisper.MaxMessageSize() {
            log.Warn("oversized message received", "peer", p.peer.ID())
            return errors.New("oversized message received")
        }

        switch packet.Code {
        case statusCode:
            // this should not happen, but no need to panic; just ignore this message.
            log.Warn("unxepected status message received", "peer", p.peer.ID())
        case messagesCode:
            // decode the contained envelopes
            var envelopes []*Envelope
            if err := packet.Decode(&envelopes); err != nil {
                log.Warn("failed to decode envelopes, peer will be disconnected", "peer", p.peer.ID(), "err", err)
                return errors.New("invalid envelopes")
            }

            trouble := false
            for _, env := range envelopes {
                cached, err := whisper.add(env, whisper.LightClientMode())
                if err != nil {
                    trouble = true
                    log.Error("bad envelope received, peer will be disconnected", "peer", p.peer.ID(), "err", err)
                }
                if cached {
                    p.mark(env)
                }
            }

            if trouble {
                return errors.New("invalid envelope")
            }
        case powRequirementCode:
            s := rlp.NewStream(packet.Payload, uint64(packet.Size))
            i, err := s.Uint()
            if err != nil {
                log.Warn("failed to decode powRequirementCode message, peer will be disconnected", "peer", p.peer.ID(), "err", err)
                return errors.New("invalid powRequirementCode message")
            }
            f := math.Float64frombits(i)
            if math.IsInf(f, 0) || math.IsNaN(f) || f < 0.0 {
                log.Warn("invalid value in powRequirementCode message, peer will be disconnected", "peer", p.peer.ID(), "err", err)
                return errors.New("invalid value in powRequirementCode message")
            }
            p.powRequirement = f
        case bloomFilterExCode:
            var bloom []byte
            err := packet.Decode(&bloom)
            if err == nil && len(bloom) != BloomFilterSize {
                err = fmt.Errorf("wrong bloom filter size %d", len(bloom))
            }

            if err != nil {
                log.Warn("failed to decode bloom filter exchange message, peer will be disconnected", "peer", p.peer.ID(), "err", err)
                return errors.New("invalid bloom filter exchange message")
            }
            p.setBloomFilter(bloom)
        case p2pMessageCode:
            // peer-to-peer message, sent directly to peer bypassing PoW checks, etc.
            // this message is not supposed to be forwarded to other peers, and
            // therefore might not satisfy the PoW, expiry and other requirements.
            // these messages are only accepted from the trusted peer.
            if p.trusted {
                var envelope Envelope
                if err := packet.Decode(&envelope); err != nil {
                    log.Warn("failed to decode direct message, peer will be disconnected", "peer", p.peer.ID(), "err", err)
                    return errors.New("invalid direct message")
                }
                whisper.postEvent(&envelope, true)
            }
        case p2pRequestCode:
            // Must be processed if mail server is implemented. Otherwise ignore.
            if whisper.mailServer != nil {
                var request Envelope
                if err := packet.Decode(&request); err != nil {
                    log.Warn("failed to decode p2p request message, peer will be disconnected", "peer", p.peer.ID(), "err", err)
                    return errors.New("invalid p2p request")
                }
                whisper.mailServer.DeliverMail(p, &request)
            }
        default:
            // New message types might be implemented in the future versions of Whisper.
            // For forward compatibility, just ignore.
        }

        packet.Discard()
    }
}

// add inserts a new envelope into the message pool to be distributed within the
// whisper network. It also inserts the envelope into the expiration pool at the
// appropriate time-stamp. In case of error, connection should be dropped.
// param isP2P indicates whether the message is peer-to-peer (should not be forwarded).
func (whisper *Whisper) add(envelope *Envelope, isP2P bool) (bool, error) {
    now := uint32(time.Now().Unix())
    sent := envelope.Expiry - envelope.TTL

    if sent > now {
        if sent-DefaultSyncAllowance > now {
            return false, fmt.Errorf("envelope created in the future [%x]", envelope.Hash())
        }
        // recalculate PoW, adjusted for the time difference, plus one second for latency
        envelope.calculatePoW(sent - now + 1)
    }

    if envelope.Expiry < now {
        if envelope.Expiry+DefaultSyncAllowance*2 < now {
            return false, fmt.Errorf("very old message")
        }
        log.Debug("expired envelope dropped", "hash", envelope.Hash().Hex())
        return false, nil // drop envelope without error
    }

    if uint32(envelope.size()) > whisper.MaxMessageSize() {
        return false, fmt.Errorf("huge messages are not allowed [%x]", envelope.Hash())
    }

    if envelope.PoW() < whisper.MinPow() {
        // maybe the value was recently changed, and the peers did not adjust yet.
        // in this case the previous value is retrieved by MinPowTolerance()
        // for a short period of peer synchronization.
        if envelope.PoW() < whisper.MinPowTolerance() {
            return false, fmt.Errorf("envelope with low PoW received: PoW=%f, hash=[%v]", envelope.PoW(), envelope.Hash().Hex())
        }
    }

    if !BloomFilterMatch(whisper.BloomFilter(), envelope.Bloom()) {
        // maybe the value was recently changed, and the peers did not adjust yet.
        // in this case the previous value is retrieved by BloomFilterTolerance()
        // for a short period of peer synchronization.
        if !BloomFilterMatch(whisper.BloomFilterTolerance(), envelope.Bloom()) {
            return false, fmt.Errorf("envelope does not match bloom filter, hash=[%v], bloom: \n%x \n%x \n%x",
                envelope.Hash().Hex(), whisper.BloomFilter(), envelope.Bloom(), envelope.Topic)
        }
    }

    hash := envelope.Hash()

    whisper.poolMu.Lock()
    _, alreadyCached := whisper.envelopes[hash]
    if !alreadyCached {
        whisper.envelopes[hash] = envelope
        if whisper.expirations[envelope.Expiry] == nil {
            whisper.expirations[envelope.Expiry] = mapset.NewThreadUnsafeSet()
        }
        if !whisper.expirations[envelope.Expiry].Contains(hash) {
            whisper.expirations[envelope.Expiry].Add(hash)
        }
    }
    whisper.poolMu.Unlock()

    if alreadyCached {
        log.Trace("whisper envelope already cached", "hash", envelope.Hash().Hex())
    } else {
        log.Trace("cached whisper envelope", "hash", envelope.Hash().Hex())
        whisper.statsMu.Lock()
        whisper.stats.memoryUsed += envelope.size()
        whisper.statsMu.Unlock()
        whisper.postEvent(envelope, isP2P) // notify the local node about the new message
        if whisper.mailServer != nil {
            whisper.mailServer.Archive(envelope)
        }
    }
    return true, nil
}

// postEvent queues the message for further processing.
func (whisper *Whisper) postEvent(envelope *Envelope, isP2P bool) {
    if isP2P {
        whisper.p2pMsgQueue <- envelope
    } else {
        whisper.checkOverflow()
        whisper.messageQueue <- envelope
    }
}

// checkOverflow checks if message queue overflow occurs and reports it if necessary.
func (whisper *Whisper) checkOverflow() {
    queueSize := len(whisper.messageQueue)

    if queueSize == messageQueueLimit {
        if !whisper.Overflow() {
            whisper.settings.Store(overflowIdx, true)
            log.Warn("message queue overflow")
        }
    } else if queueSize <= messageQueueLimit/2 {
        if whisper.Overflow() {
            whisper.settings.Store(overflowIdx, false)
            log.Warn("message queue overflow fixed (back to normal)")
        }
    }
}

// processQueue delivers the messages to the watchers during the lifetime of the whisper node.
func (whisper *Whisper) processQueue() {
    var e *Envelope
    for {
        select {
        case <-whisper.quit:
            return

        case e = <-whisper.messageQueue:
            whisper.filters.NotifyWatchers(e, false)

        case e = <-whisper.p2pMsgQueue:
            whisper.filters.NotifyWatchers(e, true)
        }
    }
}

// update loops until the lifetime of the whisper node, updating its internal
// state by expiring stale messages from the pool.
func (whisper *Whisper) update() {
    // Start a ticker to check for expirations
    expire := time.NewTicker(expirationCycle)

    // Repeat updates until termination is requested
    for {
        select {
        case <-expire.C:
            whisper.expire()

        case <-whisper.quit:
            return
        }
    }
}

// expire iterates over all the expiration timestamps, removing all stale
// messages from the pools.
func (whisper *Whisper) expire() {
    whisper.poolMu.Lock()
    defer whisper.poolMu.Unlock()

    whisper.statsMu.Lock()
    defer whisper.statsMu.Unlock()
    whisper.stats.reset()
    now := uint32(time.Now().Unix())
    for expiry, hashSet := range whisper.expirations {
        if expiry < now {
            // Dump all expired messages and remove timestamp
            hashSet.Each(func(v interface{}) bool {
                sz := whisper.envelopes[v.(common.Hash)].size()
                delete(whisper.envelopes, v.(common.Hash))
                whisper.stats.messagesCleared++
                whisper.stats.memoryCleared += sz
                whisper.stats.memoryUsed -= sz
                return false
            })
            whisper.expirations[expiry].Clear()
            delete(whisper.expirations, expiry)
        }
    }
}

// Stats returns the whisper node statistics.
func (whisper *Whisper) Stats() Statistics {
    whisper.statsMu.Lock()
    defer whisper.statsMu.Unlock()

    return whisper.stats
}

// Envelopes retrieves all the messages currently pooled by the node.
func (whisper *Whisper) Envelopes() []*Envelope {
    whisper.poolMu.RLock()
    defer whisper.poolMu.RUnlock()

    all := make([]*Envelope, 0, len(whisper.envelopes))
    for _, envelope := range whisper.envelopes {
        all = append(all, envelope)
    }
    return all
}

// isEnvelopeCached checks if envelope with specific hash has already been received and cached.
func (whisper *Whisper) isEnvelopeCached(hash common.Hash) bool {
    whisper.poolMu.Lock()
    defer whisper.poolMu.Unlock()

    _, exist := whisper.envelopes[hash]
    return exist
}

// reset resets the node's statistics after each expiry cycle.
func (s *Statistics) reset() {
    s.cycles++
    s.totalMessagesCleared += s.messagesCleared

    s.memoryCleared = 0
    s.messagesCleared = 0
}

// ValidatePublicKey checks the format of the given public key.
func ValidatePublicKey(k *ecdsa.PublicKey) bool {
    return k != nil && k.X != nil && k.Y != nil && k.X.Sign() != 0 && k.Y.Sign() != 0
}

// validatePrivateKey checks the format of the given private key.
func validatePrivateKey(k *ecdsa.PrivateKey) bool {
    if k == nil || k.D == nil || k.D.Sign() == 0 {
        return false
    }
    return ValidatePublicKey(&k.PublicKey)
}

// validateDataIntegrity returns false if the data have the wrong or contains all zeros,
// which is the simplest and the most common bug.
func validateDataIntegrity(k []byte, expectedSize int) bool {
    if len(k) != expectedSize {
        return false
    }
    if expectedSize > 3 && containsOnlyZeros(k) {
        return false
    }
    return true
}

// containsOnlyZeros checks if the data contain only zeros.
func containsOnlyZeros(data []byte) bool {
    for _, b := range data {
        if b != 0 {
            return false
        }
    }
    return true
}

// bytesToUintLittleEndian converts the slice to 64-bit unsigned integer.
func bytesToUintLittleEndian(b []byte) (res uint64) {
    mul := uint64(1)
    for i := 0; i < len(b); i++ {
        res += uint64(b[i]) * mul
        mul *= 256
    }
    return res
}

// BytesToUintBigEndian converts the slice to 64-bit unsigned integer.
func BytesToUintBigEndian(b []byte) (res uint64) {
    for i := 0; i < len(b); i++ {
        res *= 256
        res += uint64(b[i])
    }
    return res
}

// GenerateRandomID generates a random string, which is then returned to be used as a key id
func GenerateRandomID() (id string, err error) {
    buf, err := generateSecureRandomData(keyIDSize)
    if err != nil {
        return "", err
    }
    if !validateDataIntegrity(buf, keyIDSize) {
        return "", fmt.Errorf("error in generateRandomID: crypto/rand failed to generate random data")
    }
    id = common.Bytes2Hex(buf)
    return id, err
}

func isFullNode(bloom []byte) bool {
    if bloom == nil {
        return true
    }
    for _, b := range bloom {
        if b != 255 {
            return false
        }
    }
    return true
}

func BloomFilterMatch(filter, sample []byte) bool {
    if filter == nil {
        return true
    }

    for i := 0; i < BloomFilterSize; i++ {
        f := filter[i]
        s := sample[i]
        if (f | s) != f {
            return false
        }
    }

    return true
}

func addBloom(a, b []byte) []byte {
    c := make([]byte, BloomFilterSize)
    for i := 0; i < BloomFilterSize; i++ {
        c[i] = a[i] | b[i]
    }
    return c
}