Video and slides synchronized, mp3 and slide download available at URL https://bit.ly/2N37j6N. Chris Pacia takes a deep dive into libp2p, a modular networking stack written by the IPFS team, and explains how it solves the common challenges. He walks through an example atomic swap app which builds on libp2p. Filmed at qconnewyork.com. Chris Pacia is the lead back-end developer for OB1, which builds OpenBazaar, a decentralized ecommerce marketplace using cryptocurrency.

1. @chrispacia - Lead backend dev OpenBazaar
How to Leverage Libp2p for
blockchain applications

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Watch the video with slide
synchronization on InfoQ.com!
https://www.infoq.com/presentations/
blockchain-libp2p

3. Presented at QCon New York
www.qconnewyork.com
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Strategy
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Highlights
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- held in 9 cities worldwide

4. What

5. Common Needs
● Identity
● Peer discovery
● Routing
● Wire encryption/authentication
● Multi-transport
● Nat traversal
● Stream/protocol multiplexing
● Relaying

6. Languages

7. Architecture
Transport agnostic
● transports: TCP, UDP, SCTP, UDT, uTP, QUIC,
SSH, etc.
● authenticated transports: TLS, DTLS, CurveCP,
SSH

8. Multiaddr
● Support addresses for any network protocol.
● Are self-describing.
● Conform to a simple syntax, making them trivial to parse and
construct.
● Have human-readable and efficient machine-readable
representations.
● Encapsulate well, allowing trivial wrapping and unwrapping of
encapsulation layers.
/ip6/fe80::8823:6dff:fee7:f172/tcp/4001
/ip4/162.246.145.218/udp/4001/utp
/onion/erhkddypoy6qml6h:4003
/ip6/2601:9:4f81:9700:803e:ca65:66e8:c21/udp/1234/quic

10. Multihash
Format
<varint hash function code><varint digest size in bytes><hash function output>
Examples
# sha1 - 0x11 - sha1("multihash")
111488c2f11fb2ce392acb5b2986e640211c4690073e # sha1 in hex
CEKIRQXRD6ZM4OJKZNNSTBXGIAQRYRUQA47A==== # sha1 in base32
5dsgvJGnvAfiR3K6HCBc4hcokSfmjj # sha1 in base58
ERSIwvEfss45KstbKYbmQCEcRpAHPg== # sha1 in base64
# sha2-256 0x12 - sha2-256("multihash")
12209cbc07c3f991725836a3aa2a581ca2029198aa420b9d99bc0e131d9f3e2cbe47 # sha2-256 in hex
CIQJZPAHYP4ZC4SYG2R2UKSYDSRAFEMYVJBAXHMZXQHBGHM7HYWL4RY= # sha256 in base32
QmYtUc4iTCbbfVSDNKvtQqrfyezPPnFvE33wFmutw9PBBk # sha256 in base58
EiCcvAfD+ZFyWDajqipYHKICkZiqQgudmbwOEx2fPiy+Rw== # sha256 in base64

12. Architecture
Multiplexing
● can multiplex multiple listen network interfaces
● can multiplex multiple transport protocols
● can multiplex multiple connections per peer
● can multiplex multiple client protocols
● can multiplex multiple streams per protocol, per
connection (SPDY, HTTP2, QUIC, SSH)
● has flow control (backpressure, fairness)
● encrypts each connection with a different
ephemeral key

13. Protocol Muxing

14. Architecture
Encryption
Communications on libp2p may be:
● encrypted
● signed (not encrypted)
● clear (not encrypted, not signed)

16. Architecture
Nat Traversal / Relay
Multiaddr Format
[<relay peer multiaddr>]/p2p-circuit/<destination peer multiaddr>
Examples
/p2p-circuit/p2p/QmVT6GYwjeeAF5TR485Yc58S3xRF5EFsZ5YAF4VcP3URHt - Arbitrary relay node
/ip4/127.0.0.1/tcp/5002/p2p/QmdPU7PfRyKehdrP5A3WqmjyD6bhVpU1mLGKppa2FjGDjZ/p2p-
circuit/p2p/QmVT6GYwjeeAF5TR485Yc58S3xRF5EFsZ5YAF4VcP3URHt - Specific relay node

17. Architecture
Routing
● Kademlia DHT
● Supernode
● MDNS
● Other

18. Routing
Lightning Network
02212d3ec887188b284dbb7b2e6eb40629a6e14fb049673f22d2a0aa05f902090e@162.246.145.218
Libp2p
QmYMR9kDCSF3yBVVyhsRepJC4Byx6TrYGbjZsBgzVP9rG2
[
“/ip4/127.0.0.1/tcp/4001”,
“/ip4/127.0.0.1/tcp/9005/ws”
“/ip4/10.0.0.8/tcp/4001”,
“/ip4/10.0.0.8/tcp/4001/ws”,
“/ip6/::1/tcp/4001”,
“/ip6/::1/tcp/9005/ws”,
“/ip6/Fe80::8823:6dff:fee7:f172/tcp/9005/ws”,
“/onion/erhkddypoy6qml6h:4003”
]

19. Architecture
Pubsub
Propagate information throughout the network in a structured manner, with or without guarantees
like: order, delivery, efficiency, fault tolerance and so on.
● floodsub
● multicast

20. Example
- Identity
- DHT
- Protocol multiplexing
- Wire encryption
- Pubsub

21. Further Reading
https://libp2p.io/
https://github.com/libp2p
@chrispacia
ctpacia@gmail.com

22. Watch the video with slide
synchronization on InfoQ.com!
https://www.infoq.com/presentations/
blockchain-libp2p