Metadata in the Blockchain: The OP_RETURN Explosion

Metadata in the Blockchain:
The OP_RETURN Explosion
Coin Sciences Ltd
http://coinspark.org/

If Bitcoin = Gold 2.0 then …
What is the intrinsic
value of a bitcoin?
Coin Sciences Ltd Metadata in the Blockchain http://coinspark.org/

What has gone wrong? (1)

Early Internet growth
http://homes.cs.washington.edu/~lazowska/faculty.lecture/
innovation/hpcc/internet/hosts.html

Gartner hype cycle

3% (PayPal)

What is bitcoin for?

Bitcoin as communication

What can we send?
An expensive way to encode information

Fake addresses
Permanent burden on unspent output list

Multisig addresses (1 of …)
Temporary burden on unspent output list

The OP_RETURN decision
https://bitcoinfoundation.org/2013/10/core-development-update-5/

OP_RETURNs
Provably prunable, no unspent output

OP_RETURN size limit

OP_RETURNs vs TCP/IP
OP_RETURNs TCP/IP Ratio
Address space 2160 (collisions) 232 → 2128 1×
Latency 5 seconds 1 second 5×
Packet size 40 bytes 1.5 KB 36×
Bandwidth ~100 bytes/s
(50% of network!)
5 MB/s
(50% of 100 Mbps)
50,000×
Cost $850,000/GB
(at $315/BTC)
$0.10/GB 10,000,000×

Asynchronicity?
Bitcoin TCP/IP Email
Asynchronous Synchronous Asynchronous

Notarization
Bitcoin TCP/IP
Blockchain None

Message chaining
Bitcoin TCP/IP
Directed acyclic
graph
Request-response
only

Privacy
Bitcoin TCP/IP
Addresses
Pseudonymous
but transaction
chain analysis
IP geolocation,
traceable to
individual via ISP
Payloads Naked in public
Private but seen
by ISPs, switches

Payment model
Bitcoin TCP/IP
Per message,
with message
Subscription or pay-
per-use, separate

So bitcoin is suitable for…
•  Tiny payload
•  High value
– Hashes in general
•  Public broadcast
•  Permanently recorded
•  Non-instant
•  Pay-as-you-go

Financial transactions

Document notarization
Bitproof, BlockSign, La Preuve, ProveBit,
Proof of Existence, Stampd, Stampery

Historical records
•  Blog post about stuff in blockchain
Lots more: http://www.righto.com/2014/02/
ascii-bernanke-wikileaks-photographs.html

Email with scarcity?

Universal family tree?
•  Show a family tree (DAG)
http://recursivediscursion.blogspot.com/2011/04/gentle-introduction-to-graph-theory.html

0
5
10
15
20
25xxxx
26xxxx
27xxxx
28xxxx
29xxxx
30xxxx
31xxxx
32xxxx
33xxxx
34xxxx
35xxxx
36xxxx
37xxxx
Bitcoin block numbers (each column ~70 days)
OP_RETURNs per block
Bitcoin 0.9 released
19th March 2014
More at:
coinsecrets.org

OP_RETURNs to block 375000
27%
17%
9%
3%2%
2%
40%
Open%Assets%
Blockchain%ID%
CoinSpark%
Ascribe%
Proof%of%Existence%
Factom%
Other%

CoinSpark
•  Rich OP_RETURN protocol
– Multiple metadata per OP_RETURN
•  Version 1.0 — September 2014
– Assets = lightweight scalable colored coins
– Payment references
•  Version 2.0 — February 2015
– Transaction attachments / messaging
•  Version 3.0: simpler addressing, …

CoinSpark assets
•  Assets via OP_RETURN metadata
– Not connected to bitcoin quantity
•  Genesis metadata:
– Quantity, issuer transaction fees
– Compressed web page URL
– Hash of contract and key params
•  Transfer metadata:
– Reference to genesis, quantity, outputs

CoinSpark assets for users
•  Lightweight wallet
•  Asset web page
– View in browser
– Hidden metadata
– Domain authenticates issuer
•  Asset contract
– Ready US + UK templates
– Customizable

SparkBit wallet

Asset web page

Asset contract

Bitcoin transaction model
Signed by Alice
Alice 10.000
Bob 2.000
Alice 7.999
Miner 0.001

CoinSpark asset model
•  Multiple assets per output
– Low burden on network
– No accidental loss
•  Default: all assets to last output
•  Metadata sends to other outputs
– 40 bytes: up to 3 assets, unlimited outputs
•  Asset independence ⇒ scalability
– Issuer provides tracking server for SPV

Example asset transaction
Signed by Alice
Alice 0.007
Bob 0.001
Alice 0.005
OP_RETURN
Miner 0.001
A
B
C
B
A
C
B
Output 1
150
60
60
90

CoinSpark messages
•  Attach text and/or files to a bitcoin or
CoinSpark asset transaction
•  Message discovery via OP_RETURN
– Compressed URL / IP of delivery server
– Outputs for which message intended
– Hash of message + salt
•  Open source delivery server
– Federated, non-centralized model

CoinSpark messages vs email
•  Hash proves message authenticity
•  Notarization of message on blockchain
– Contracts, invoices, digital delivery
•  Also: public messages
– Broadcast content + proof of existence
•  Future: message encryption
– Requires public key, not just bitcoin address
•  Challenge: identity (Openname?)

CoinSpark OP_RETURN format
53
50
4B
CoinSpark marker (“SPK”)
61
FF
— Last metadata opcode
···· Last metadata (until end of script)
01
60
Length of this metadata section—
61
FF
— Metadata opcode
···· Metadata (up to 95 bytes)
＊

Metadata opcodes
61
7F
—
67

72

74

80
EF
—
Reserved for CoinSpark
Asset genesis (“g”)
Payment reference (“r”)
Asset transfer (“t”)
Your application?
6D
Message pointer (“m”)

Every byte is sacred

Only encode surprises
000 = omit fields. If this is the first color transfer, assume input and output indices of 0.
Otherwise take the indices from the previous color transfer.
001 = omit fields. If this is the first color transfer, assume input index 0 and output index
1. Otherwise take the indices from the previous color transfer and increment the output
index only.
010 = omit fields. If this is the first color transfer, assume input index 1 and output index
0. Otherwise take the indices from the previous color transfer and increment the input
index only.
011 = omit input index and use 1 byte for output index. If this is the first color transfer,
assume input index 0. Otherwise use the same input index as the previous color transfer.
100 = omit output index and use 1 byte for input index. If this is the first color transfer,
assume output index 0. Otherwise use the same output index as the previous color
transfer.
101 = use 1 byte for input index, 1 byte for output index.
110 = use 1 byte for input index, 2 bytes for output index.
111 = use 2 bytes for input index, 2 bytes for output index.

Mantissa and exponent
625 trillion = 625×1012
??11001001110001

Common domain strings
www.

.at

.au

.be

.biz

.br

.ca

.ch

.cn

.co.jp

.co.kr

.co.uk

.co.za

.co

.com.ar

.com.au

.com.br

.com.cn

.com.mx

.com.tr

.com.tw

.com.ua

.com

.cz

.de

.dk

.edu

.es

.eu

.fr

.gov

.gr

.hk

.hu

.il

.in

.info

.ir

.it

.jp

.kr

.me

.mx

.net

.nl

.no

.org

.pl

.ps

.ro

.ru

.se

.sg

.tr

.tv

.tw

.ua

.uk

.us

.vn


More domain name compression
•  38 valid characters
– 0 to 9, a to z, -‐ .

•  Two terminator characters ⇒ 40
– http:// vs https://

•  403 = 64000 < 65536 = 216
– So 3 characters per byte pair
•  Special case: IPv4 address
– Obvious encoding in 4 bytes

Variable hash length ≥ 96 bits
350,000,000 × 109 × 86400 × 365 × 7178 = 296

CoinSpark for Developers
•  Fully open source (MIT/AGPL)
•  Multilingual libraries
– C/C++, Go, Java, JS, PHP, Python, Ruby
•  Fully decentralized
– Server-side elements federated
• Let’s do for bitcoin what
the web did for TCP/IP

Back to the start…
What is the intrinsic
value of a bitcoin?

0.0
0.2
0.4
0.6
0.8
1.0
1.2
2011 2012 2013 2014 2015 2016 2017 2018 2019
Average block size (MB)
Current limit: 1 MB
Economic
prehistory
Economic
reality

What happens then?
•  Transactions compete for confirmation
– Bidding via miner fee, paid only in bitcoin
•  Real price discovery
– Econ 101: until supply = demand
•  If enough transactions (notarization?) are
worth $10 to sender, all will cost that
– No more cups of coffee!
•  Increasing block size limit just delays this

So: bitcoin = global
bidding power for
embedding data in
the blockchain.

MultiChain
•  Private blockchain platform
– Targeted at financial sector
– Drop-in replacement for Bitcoin Core
•  Easy and quick deployment
– Custom network parameters
•  Permission management
•  Native asset support
•  Stable alpha now available

Coin Secrets – coinsecrets.org

php|python-OP_RETURN
•  Send OP_RETURN using Bitcoin Core
– Doing it yourself is hard work!
•  Store and retrieve any data in blockchain
– Uses OP_RETURNs in chained transactions
– Returns reference like 356115-052075 for
easy and fast retrieval
•  Use on command line or library
– PHP and Python now, Ruby to come

Metadata in the Blockchain: The OP_RETURN Explosion

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