One of the biggest innovations of the recent technological landscape is definitely represented by bitcoin and the technology that stands behind it: blockchain. Beyond its revolutionary financial executions, solutions regarding timestamping are born. In this presentation, we are going to analyze trustless timestamping properties comparing them to the actual competitor technologies, as well as taking a deep dive in the OpenTimestamps protocol.

1. BLOCKCHAIN & CRYPTO VALUES CONF | June 14 - Milan
OpenTimestamps:
from postmarks to blockchain
Riccardo Casatta - CEO - Eternity Wall

2. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Agenda
● Eternity Wall history
● Timestamping
● OpenTimestamps
● Use cases

3. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Agenda
● Eternity Wall history
○ From messages to timestamping
● Timestamping
● OpenTimestamps
● Use cases

4. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
The story so far... July 10, 2014

5. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
How it all started May 27, 2015
Bitcoin Mom loves Willb20c

6. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
From idea to execution June 24, 2015

7. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
The first...

8. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
...the many

9. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta

10. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
What now?
● Message are super cool and still running (for the
eternity!)
● With the gained experience we are moving to a
more general and business-oriented concept
Timestamping!

11. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Workshop Agenda
● Eternity Wall history
● Timestamping
○ What’s timestamping?
○ From analog to digital
○ How we can use blockchain?
○ From trusted to trustless
● OpenTimestamps
● Use cases

12. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
What’s timestamping?
● A timestamp proves that a message existed prior to
some point in time
● Historically the postmark of the postal office
○ It doesn’t help if the stamp is on the envelope
● What about digital documents?

13. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
What’s digital timestamping?
● Based on digital signature of a third party
● Based on certification authority
○ Eg. Italian PEC

14. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
How we can use Blockchain for timestamping?
Newer
blocks
Time
t0
t1
t2
Genesis
block

15. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
How we can use Blockchain for timestamping?
Newer
blocks
Time
t0
t1
t2
t3
Genesis
block
Hash
Tx

16. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
How we can use Blockchain for timestamping?
Time
t0
t1
t2
t3
Genesis
block
t4
t5
t6
t7

17. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Why Blockchain?
● Digital timestamping
○ Require third party (trusted timestamping)
■ Increase costs
○ Requires digital signature which requires to store a secret
■ Increase risks

18. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Timestamping with digital signature
What if the timestamper’s private key is stolen?
The key revocation certificate is issued and timestamps after the theft are
considered invalid

19. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Timestamping with digital signature
What if the timestamper’s private key is stolen?
The key revocation certificate is issued and timestamps after the theft are
considered invalid
WRONG
Every timestamp created by that key has to be considered invalid because the
thief can backdate timestamps
Digitally signed timestamps are as safe as the signing key

20. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Timestamping with digital signature
X X
time
Could re-forge any document

21. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Trustless timestamping
✓ ✓
time

22. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta

23. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Trustless timestamping
✓ X
time
Could not back-forge documents

24. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
● Eternity Wall history
● Timestamping
● OpenTimestamps
○ What’s OpenTimestamps
○ From one-tx-one-timestamp to aggregating timestamp (merkle tree)
○ Architecture: Blockchain, receipts, clients, calendar servers & backups
● Use cases
Agenda

25. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Trustless timestamping standard
● Fully open-source
● Could work without third parties (only blockchain)
● Free to use (without SLA) and “cheap” for the blockchain
● Already used by big corps

26. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Aggregating
Timestamps
Bitcoin Block Header
TxA
TxB
TxC
TxD
HASH
H(TxA
) H(TxB
) H(TxC
) H(TxD
)
HASH HASH HASH
H(H(TxC
)|H(TxD
))H(H(TxA
)|H(TxB
))
HASH HASH
Merkle Root
HASH
Previous Block Header Hash
Version Time nBits Nonce
Transactions

27. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Aggregating
Timestamps
Transactions Documents

28. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Aggregating
Timestamps
✓ scalability &
independence
Transactions Documents

29. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Aggregating Timestamps
Newer
blocks
Time
t0
t1
t2
t3
Genesis
block
Hash
Tx

30. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Aggregating Timestamps
Newer
blocks
Time
t0
t1
t2
t3
Genesis
block
Tx

31. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Aggregating Timestamps
Newer
blocks
Time
t0
t1
t2
t3
Genesis
block
Tx

32. OpenTimestamps phases
File
Hash 0xA...
Hash 0xC...
Hash 0xF...
Hash 0xG...
Hash 0xD...Hash 0xB...
Hash 0xE...
Hash 0xA...
1) calculate hash
2) copy hash in the merkle tree
0 1 2 3 4 5 6 7 8 9
4) Push the transaction on the blockchain
Proof
3) send the proof
time
Client
Calendar server
Blockchain
5) upgrade the proof

33. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
OpenTimestamps is
flexible

34. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
OpenTimestamps Libraries
https://github.com/opentimestamps

35. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
OpenTimestamps Calendar Servers
● Maintained by different entities
○ https://alice.btc.calendar.opentimestamps.org/
○ https://bob.btc.calendar.opentimestamps.org/
○ https://finney.calendar.eternitywall.com/
○ https://btc.calendar.catallaxy.com/
● Offering their state publicly (all performed timestamp)
○ Through the /calendar URI
● Publicly backup-able
● Also the server is open-source

36. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
OpenTimestamps Performances
https://blog.eternit
ywall.com/2017/06
/22/opentimestam
p-performances/

37. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
● Eternity Wall history
● Timestamping
● OpenTimestamps
● Use cases
Agenda

38. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Simplest use case, this presentation!
$ npm install -g javascript-opentimestamps
$ ots-cli.js stamp OpenTimestamps_from_postmarks_to_blockchain.pdf
The timestamp proof 'OpenTimestamps_from_postmarks_to_blockchain.pdf' has been
created!
$ ots-cli.js info 'OpenTimestamps_from_postmarks_to_blockchain.pdf.ots
...
$ ots-cli.js upgrade OpenTimestamps_from_postmarks_to_blockchain.pdf.ots
$ ots-cli.js verify OpenTimestamps_from_postmarks_to_blockchain.pdf.ots
Success! Bitcoin block NNN attests existence as of YYYY-MM-DD CEST
Attribution 3.0 Unported (CC BY 3.0)
1
2
3

39. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Timestamping the Internet use case
● Being honest, we are talking about archive.org and its
wayback machine (_only_ 50 Petabytes)
● Can archive.org collude?
● Practical demonstration of scalability, client merkle tree of
750M items
● Sha1!?!? Shattered? Ok for timestamping!
Hackabit 23 June 2017

40. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Regulators use case
● Dodd-Frank requires trade reconstruction data to be stored on supports
satisfying some properties
○ WORM Write Once Read Many
○ Anti tamper
● Today, regulated entities use third party services relying on security by
certification authority and digital signature
○ Does not solve double spend!

41. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Regulators use case
By trustless timestamping we
achieve the same anti-tamper
and WORM property with less
operational costs and more
security

42. Q&A
THANK YOU
For more questions write to riccardo@eternitywall.com

43. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
OpenTimestamps
● Blockchain is permissionless
○ Anyone with bitcoin could timestamp something
■ Costs while aggregation
■ Banks have compliance problems
● OpenTimestamps is a standard way of doing trustless timestamping
○ Proposed by Peter Todd, I am the first contributor
○ Supports different blockchains
○ Increase startup credibility and reliability as a service provider

44. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Timestamping and
proof of publication
● Timestamping
○ An external viewer could not see all the element of the set
■ If someone timestamp two different version of a document,
the rest of the world cannot see it
● Proof of publication
○ An external viewer could see all the the element of the set
■ Prevent double spend!
■ Bitcoin UTXO (Unspent Transaction Output)
■ Very Expensive!

45. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
What are the Notary’s functions?
● Checking the act validity with law
○ Blockchain KO
● Stamping the act for integrity and datation
○ Timestamping OK
● Publishing the act in the notary public archive
○ Timestamping not enough

46. Eternity Wall - https://eternitywall.com | OpenTimestamps - https://opentimestamps.org | Riccardo Casatta - @RCasatta
Is this legal?
● There are no precedent yet here in Italy
● Civil code provides way to identify a date
○ Connected to a public event
○ Public event -> Block publishing!