The document describes Whisper, a hybrid decentralized network (DHT) and messaging system that provides private and authenticated communications. It functions as both a data storage system through topics and as an asynchronous messaging transport. Key features include probabilistic message forwarding for privacy, configurable topic-based filtering, proof-of-work for anti-DoS, and identity-focused design without exposing endpoints.

1. Whisper
What and Why

2. Consensus is Expensive
Avoid use for pure comms

3. Comms patterns in MMUs
Static content publication
e.g. BitTorrent, FTP
Connection (betwixt identities)
e.g. VoIP, RTC
Transient Datagrams
e.g. Twitter, IM, registries

4. Datagram patterns in MMUs
Wholly directed
e.g. IM, e-mail
Partially directed
e.g. Mailing list, usenet
Filterable global
e.g. Twitter, registries, content-search

5. Static Content
DHT/Swarm
(See later talk)

6. RTC Connection
Raw P2P Connection
Thin layer over ÐΞVp2p

7. Routing privacy is
important
Encryption alone won’t keep your
information safe

8. Whisper
Hybrid DHT and messaging system
Dark
...probabilistic message forwarding
Subject-key orientated
...no indication of encryption, no notion of recipient

9. Is it a DHT?
Multi-key
...many ‘topics’ associated with entries
Multi-value
...many entries can have the same key-set
Transient
...entries have explicit expiry

10. Is it a Datagram Transport Layer?
Broadcast/multicast/unicast
...always secure & authenticated
Asynchronous
...packets have a TTL

11. Anti-DoS/SPAM
Proof-of-work,
good-behaviour incentivisation

12. Always Identity,
Never Endpoint
Endpoint is implementation detail

13. Configurable
User makes efficiency/privacy tradeoff

14. Topic-based
Watch for topic subsets, act accordingly

15. Secure
Unicast vs broadcast = Encrypted vs plain

16. Authenticated
Origin vs anonymous = Signed vs unsigned

17. What it’s not
Point-to-point
High bandwidth
Low latency
Application-level
Connection-oriented

18. Two Routes to Routing
Passive
...peer steering through rotation against past usefulness
Active
...topic advertising through masks

19. Prioritised Forwarding
Serve your peers well or risk disconnection
Interesting Topics
...prioritise messages in which peer has expressed interest
Lowest TTL
...prioritise short-lived messages
Highest Proof-of-Work
...prioritise messages for which a greater proof-of-work has been conducted

20. Masking/Filtering
Stacking the odds with topic masks
Configurable
...masks can use configurable number of bits to give info to peers
Customised per peer
...more trusted peers can be better informed
Customised per ÐApp
...more sensitive ÐApps can have greater privacy

21. Masking/Filtering
Forming the topic vortex
Consolidation of masks & forwarding
...masks of all other peers are consolidated packaged and resent
log(N) distance for mask precision
...information drops-off further away from peer as net increases

22. API
Three functions
newIdentity
...create a new identity (i.e. key pair)
post
...post an entry/message
watch
...watch for new entries/messages on the system

23. newIdentity
var key = newIdentity();

24. post
shh.post({
optionally "from": owned public key,
optionally "to": public key,
"topics": [ ..., ... ],
"payload": ...,
"ttl": integer,
"priority": integer
});

25. watch
var w = shh.watch({
optionally "to": owned public key,
"filter": [ ..., ... ],
});
w.changed(function(m) { ... });
var ms = w.messages();
w.uninstall();

26. Example
var myIdentity = shh.newIdentity();
shh.post({
"from": myIdentity,
"topics": [ web3.fromAscii(appName) ],
"payload": [ web3.fromAscii(myName),
web3.fromAscii("What is your name?") ],
"ttl": 100,
"priority": 1000
});
var replyWatch = shh.watch({
"filter": [ web3.fromAscii(appName), myIdentity ],
"to": myIdentity
});
replyWatch.arrived(function(m)
{
// new message m
console.log("Reply from " +
web3.toAscii(m.payload) + " whose address is " +
m.from;
});

27. Example
var broadcastWatch = shh.watch({ "filter": [
web3.fromAscii(appName) ] });
broadcastWatch.arrived(function(m)
{
if (m.from != myIdentity)
{
// new message m: someone's asking for our name. Let's
tell them.
var broadcaster = web3.toAscii(m.payload).substr(0,
32);
console.log("Broadcast from " + broadcaster + ";
replying to tell them our name.");
shh.post({
"from": eth.key,
"to": m.from,
"topics": [ eth.fromAscii(appName), m.from ],
"payload": [ eth.fromAscii(myName) ],
"ttl": 2,
"priority": 500
});
}
});

28. Not yet covered
Multicasting (shared-secret dispersal)
Plausible deniability of authoring (Daniel?)
Security, privacy and scalability modelling:
how good is it?

29. Whisper
What and Why
Questions