Slides of the keynote held at the BPM Blockchain Forum 2023, 13 September 2023, Utrecht, Netherlands. Synopsis: Multi-party business processes rely on the collaboration of various players in a decentralized setting. Blockchain technology can facilitate the automation of these processes, even in cases where trust among participants is limited. Transactions are stored in a ledger, a replica of which is retained by every node of the blockchain network. The operations saved thereby are thus publicly accessible, which benefits transparency, reliability, and persistence. Smart contracts can encode the system behavior agreed upon by the involved parties to define the behaviour of collaborative processes. Rule enforcement, traceability and non-repudiation are thus catered for, too. However, data, objects and services in the outer world are not directly accessible from within a blockchain execution evironment. On one hand, access to limited information hinders the adoption of programmable blockchains as an effective aid to process intelligence. On the other hand, transferring every bit of off-chain information on-chain is not only impractical but also undesirable, as this operation could violate typical confidentiality requirements in enterprise settings. In this talk, we discuss and explore approaches aimed at strengthening the bond between process and blockchain execution environments, balancing between knowledge sharing and secrecy preservation.

1. Look but don’t touch:
On the impalpable bond
between blockchain and
process
Claudio Di Ciccio | claudio.diciccio.net | claudio@diciccio.net
Presented works were funded by the SmartDeFi project, Spoke 09, SERICS (PE00000014), under
the NRRP MUR program funded by the EU – NextGenerationEU; project PINPOINT
(B87G22000450001), under the PRIN MUR program; the Cyber 4.0 project BRIE.

2. Claudio Di Ciccio /klˈaːudio di ˈt͡ʃiːtt͡ʃo/
Associate professor
Ph.D. in Computer Science and Engineering
Main research interests:
automated reasoning &
logic and computation,
applied in
blockchain architectures &
process analytics
Claudio Di Ciccio 13/09/2023
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3. So, what is your research about?
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Thanks to Sabrina Kirrane for the photo (2019)

4. So, what is your research about?
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Thanks to Sabrina Kirrane for the photo (2019)

5. Claudio Di Ciccio /klˈaːudio di ˈt͡ʃiːtt͡ʃo/
Associate professor
Ph.D. in Computer Science and Engineering
Main research interests:
automated reasoning &
logic and computation,
applied in
blockchain architectures &
process analytics
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6. Transaction
• Transfer of (crypto)assets (Ether, Bitcoin, Algo, …)
from account A to account B
Externally Owned
Account (EOA)
Externally Owned
Account (EOA)
Digital signature
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Transaction ID: 0xfa12…40c6da

7. Ledger
• Ordered collection of transactions
• The order matters!
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8. Amsterdam, 1856
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• About 2000 ships departed on
an annual basis
• Seafarers
 numerous
 a vital contribution to trade
 wages paid after a journey
(always in need of credit)
• Non-bank credit markets
 Shopkeepers and boarding-house
keepers as lenders
• The Discipline Act (1856)
 Forbids the use of seafarers’ wages
as redemption payments
Image source: https://www.istockphoto.com/nl/vector/amsterdam-in-the-
19th-century-gm538063610-95625387

9. The ledger of the
water bailiff’s
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• The Discipline Act prescribed
that lenders had to present
their unredeemed IOUs to the
water bailiff’s during the month
of July 1856
• Every IOU recorded basic
information, including:
 the date on which it was entered
 the names of lender and borrower
 the unredeemed amount
• 13,708 loans were registered in
a 443-page ledger
A hand-drawn ink lithography of men writing a ledger in the water bailiff's
office in 1856 (DALL-E, https://openai.com/dall-e-2/)

10. Block
• Blocks group and collate transactions
• The order matters!
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11. Hashing the previous block for immutability
• Blocks refer back to direct predecessors via hashing
• The order matters!
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12. The blockchain remembers
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13. Centralised ledger
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“In Amsterdam, the water bailiff’s office was
located in the […] middle of one of the
seafarers’ quarters […] open for registering
IOUs six days per week.
On one occasion, clerks […] worked
overtime on a Sunday: presumably
because the company of H. Lond, one of
the largest lenders in town, had delivered its
1314 unredeemed IOUs the day before and
they did not want to start the new week with
such a backlog”

14. Decentralisation for persistence
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Centralisation Decentralisation
Warning: possible information inconsistency → proof-of-* and consensus

15. Private|public / Permissioned|permissionless
Transactability / visibility
Private Public
Consensus
Permissionless
Selected nodes can
transact and view,
all nodes can
participate in consensus
Every node can
transact and view,
participate in consensus
Permissioned
Selected nodes can
transact and view, or
participate in consensus
Every node can
transact and view,
selected nodes
participate in consensus
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Anderberg et al. “Blockchain Now And Tomorrow” (2019) http://dx.doi.org/10.2760/901029

16. “A universal platform with internal
programming language, so that everyone
could write any app”
[V. Buterin]
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Claudio
Di
Ciccio
From a peer-to-peer electronic cash system
to a programmable distributed environment

17. Smart Contracts
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• Smart Contracts in Ethereum
 live in the Ethereum environment
 execute a function when called
 have direct control over their own
balance and key/value storage
 exhibit a behaviour that is fully
specified by their code

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Where are Smart Contracts
executed?
First on the mining nodes.
Then, potentially, on every node!
Only absolutely needed
instructions should be in the code!
The polygraph machine

19. Expressive power of
smart contracts
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• Variants exist
• Solidity is a Turing-complete
language for the Ethereum
blockchain
• Smart contracts can potentially
run any computable algorithm
Picture: https://doi.org/10.1093/ref:odnb/36578

20. A programmable distributed environment
Input encoded data.
Smart Contract
Account
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New
Smart Contract
Account
New address
Smart contract code to be deployed
Invoking a smart
contract function
Deploying a new
smart contract
Execution is not
externally
stoppable!

21. From high-level code to bytecode to bits and bytes
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22. A programmable distributed environment
Input encoded data.
Smart Contract
Account
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New
Smart Contract
Account
New address
Smart contract code to be deployed
Invoking a smart
contract function
Deploying a new
smart contract
Execution is not
externally
stoppable!

23. Execution is not for free
(most of all, in public blockchains)
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Wood , “Ethereum: A secure decentralised generalised transaction ledger” (2014), https://ethereum.github.com/yellowpaper/paper.pdf

24. A programmable distributed environment
Input encoded data.
Smart Contract
Account
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New
Smart Contract
Account
New address
Smart contract code to be deployed
Invoking a smart
contract function
Deploying a new
smart contract
Execution is not
externally
stoppable!
Gas price (execution costs)
Gas price (execution costs)

25. Challenges about costs
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26. Price instability of cryptocurrency and gas prices
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ETH/EUR exchange Gas price on the Ropsten testnet

27. Web 3.0 and
Decentralised applications (DApps)
31
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28. Advantages and connection to processes
• Smart contracts → Programmability → Process rule enforcing
• Transactions → Asset transfer & function invocation → Process execution
• Distributed store → Data persistency → Process monitoring
• Ledger → Transaction ordering → Logging
• Hashing → Robustness → Secure storage
• Signatures → Authentication → Non-repudiability
• Consensus → Eventual consistency → Traceability
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Images: Left: https://doi.org/10.1145/3183367; right: https://www.dagstuhl.de/en/seminars/seminar-calendar/seminar-details/18332
Layer of trust
even in a
regime of
partial trust
among actors

29. Executing inter-organisational processes on the
Blockchain: A model-driven approach
D.C, Cecconi, A., Dumas, M., et al. (2019), “Blockchain support for collaborative business processes”
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30. Executing inter-organisational processes on the
Blockchain: A model-driven approach
Caterpillar Lorikeet
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ChorChain
D.C, Cecconi, Dumas et al. Blockchain support for collaborative business processes. Informatik Spektrum pp. 1–9 (May 2019)
López-Pintado, García-Bañuelos, Dumas, Weber. Caterpillar: A blockchain-based business process management system. In: BPM Demos. CEUR.ws, 2017.
Tran, Lu, Weber. Lorikeet: A Model-Driven Engineering Tool for Blockchain-Based Business Process Execution and Asset. In: BPM Demos. CEUR.ws, 2018.
Corradini, Marcelletti, Morichetta, Polini, Re, Tiezzi: Engineering Trustable and Auditable Choreography-based Systems Using Blockchain. ACM TMIS 13(3), 2022.

31. Tracking execution
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D.C. et al. Blockchain-Based Traceability of Inter-organisational Business Processes. In: BMSD. Springer, 2018.

32. Traceability
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D.C. et al. Blockchain-Based Traceability of Inter-organisational Business Processes. In: BMSD. Springer, 2018.

33. From execution to ledgers
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Claudio Di Ciccio

34. Traceability
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https://www.sage.com/en-gb/blog/blockchain-traceability-supply-chain/ Accessed: 19/02/2020

35. From ledgers to time-ordered datasets
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36. From data sets to process mining and analytics
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37. Mining blockchain processes
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38. Mining blockchain processes
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Coming next: Towards Object-Centric Process Mining for Blockchain Applications (Hobeck, Weber)

39. OK. OK. So?
Where is the problem?
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40. Objects are central in process management
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Screenshots captured from: https://www.tf-pm.org/resources/oced-standard; https://www.ocel-standard.org/; https://objects2023.github.io/

41. Double spending
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0xA 0xB
0xC
100 ¢
10 ¢ 50 ¢
10 ¢ 140 ¢
90 ¢
50 ¢
Tx ID: 0xA90B
Tx ID: 0xA50C
X

42. Double spending
48
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0xA 0xB
0xC
100 ¢
10 ¢ 50 ¢
90 ¢
Tx ID: 0xA90B
50 ¢
Tx ID: 0xA50C

43. Double spending
49
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0xA 0xB
0xC
100 ¢
10 ¢ 50 ¢
90 ¢
Tx ID: 0xA90B
50 ¢
Tx ID: 0xA50C
60 ¢ 50 ¢
X

44. The order matters in blockchain-enabled processes
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Marco Montali presents “Reasoning about Knowledge in BPM: A Systematic Approach” at FM-BPM 2023 (BPM 2023, Utrecht)

45. The problem
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DB

46. How about the real world?
Oracles: From on-chain to off-chain and vice versa
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Claudio
Di
Ciccio

47. The Oracle
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Foundational Oracle Patterns: Connecting Blockchain to the Off-Chain World. BPM (Blockchain and RPA Forum) 2020: 35-51
DB

48. The Oracle
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Foundational Oracle Patterns: Connecting Blockchain to the Off-Chain World. BPM (Blockchain and RPA Forum) 2020: 35-51
DB
ISO/TC 307, ISO/TR 2345: “[A] DLT Oracle [is a] service that updates a distributed
ledger using data from outside the distributed ledger system”. (2019)
Previous literature: oracles as off-chain information providers.
We see oracles as a bridge
between the on-chain and off-chain worlds.

49. Oracle patterns: Overview
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Foundational Oracle Patterns: Connecting Blockchain to the Off-Chain World. BPM (Blockchain and RPA Forum) 2020: 35-51

50. Decentralised oracles
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Enhancing Blockchain-Based Processes with Decentralized Oracles. In: BPM Blockchain and RPA Forum 2021, 102-118, Springer.

51. Decentralised oracles (example: pull-in)
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Enhancing Blockchain-Based Processes with Decentralized Oracles. In: BPM Blockchain and RPA Forum 2021, 102-118, Springer.

52. Decentralised oracles (example: pull-in)
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Enhancing Blockchain-Based Processes with Decentralized Oracles. In: BPM Blockchain and RPA Forum 2021, 102-118, Springer.
Credit institute 1
Decentralized
oracle
Credit institute 3
Credit institute 2
Smart
contract

53. About privity
• Albeit very costly, we could inject all the
information we need on-chain.
• Even if we were able to inject all the data
in the world on chain, would we like the
idea?
• “Privity strives for limiting the sharing of
information within a contract to those
parties of a contract who have a
contractual need to know”
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Köpke, Franceschetti, Eder: Balancing Privity and Enforceability of BPM-Based Smart Contracts on Blockchains. BPM (Blockchain and CEE Forum) 2019: 87-102

54. While collaborators cooperate…
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Signing of the Peace Protocol Between Spain and the United States, August 12, 1898
(source: https://library.whitehousehistory.org/fotoweb/archives/5017-Digital-Library/Main%20Index/Artwork/520.tif.info)

55. … the whole network observes
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Scene from The Truman Show (1998). Image source: https://redeemingculture.com/film/drama/4106-the-truman-show-empathy-and-reality

56. The impalpable bond
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Michelangelo Buonarroti: La Creazione di Adamo (1511)

57. Fix this image in your memory
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Image source: https://www.makinggameofthrones.com/production-diary/2013/5/29/leeches-dragons-and-a-bear-behind-the-scenes-of-episodes-307.html

58. Is this the same image?
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Image source: https://www.makinggameofthrones.com/production-diary/2013/5/29/leeches-dragons-and-a-bear-behind-the-scenes-of-episodes-307.html

59. Validation v. understanding
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Image source: https://www.makinggameofthrones.com/production-diary/2013/5/29/leeches-dragons-and-a-bear-behind-the-scenes-of-episodes-307.html

60. Business Process Model and Notation (BPMN)
collaboration diagram
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anufacturer
Production order
set up
Order parts
ill of materials
echanical
parts
supplier
ill of materials
received
Electronic
parts
supplier
ill of materials
received

61. The message, in clear
(as seen by the manufacturer)
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0xfd9ffe3578a42d81c4684bd47e6575d9a8f10cc6dab984bd7e19ee0dbacb6287
Hash:

62. The message
(as seen by external parties)
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0xfd9ffe3578a42d81c4684bd47e6575d9a8f10cc6dab984bd7e19ee0dbacb6287
Hash:

63. The message
(as seen by the electronic parts supplier)
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0xfd9ffe3578a42d81c4684bd47e6575d9a8f10cc6dab984bd7e19ee0dbacb6287
Hash:

64. The message
(as seen by the mechanical parts supplier)
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0xfd9ffe3578a42d81c4684bd47e6575d9a8f10cc6dab984bd7e19ee0dbacb6287
Hash:

65. Hence the name: CAKE
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Image source: https://heriots.co.uk/products/pistachio

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• Blockchain platform
• Smart contracts
• InterPlanetary File System (IPFS)
• Ciphertext-Policy (CP) Attribute-Based Encryption (ABE)
Ingredients

67. InterPlanetary File System (IPFS)
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 Distributed system for the storage and access to files
 Content-addressing to uniquely identify each file in the network
 The resource locator is derived from the content hash
 Files scattered among several nodes
 Distributed Hash Table (DHT) at its core

68. CP-ABE
• Attribute-Based Encryption (ABE): type of public-key encryption
• Ciphertext-Policy ABE (CP):
 We associate roles and process instance ID with attributes
 (propositional literals)
 Messages are associated with policies
 (propositional formulae on attributes)
• Attributes:
14548487, Supplier, Electronics, Electronics, Manufacturer
• Policy:
14548487 AND (Manufacturer OR (Supplier AND Electronics))
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Process
instance ID
Roles

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Policy
Plaintext Ciphertext
Ciphertext Plaintext
Secret key
Attributes Secret key
1: ciphering
2: key generation
3: deciphering
https://www.iconfinder.com/
0: pre-phase
Public
key (pk)
Master public
key (mpk)
pk
pk
Key pair
Key pair
pk
mpk
CAKE Given
Attribute certification

70. Phase 0: certification
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Attribute certifier
Address: 0x123
Attributes: 14548487, Manufacturer
Address: 0x456
Attributes: 14548487, Supplier, Electronics
Address: 0x789
Attributes: 14548487, Supplier, Mechanics
Smart Contract

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Phase 1: ciphering

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Phase 1: ciphering

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14548487, Manufacturer
14548487, Supplier, Electronics
14548487, Supplier, Mechanics
D: 2nN6…GCcZ
Dj: 4558…5+Qg
Djp: 8944….5949
D: A9BS…CnoO
Dj: OQEL…1207
Djp: hI2M…. lWBb
D: 1+8Ka…kaUd
Dj: feoH…7393
Djp: bJju…. NIGw
Key pair
Key pair
Key pair
Phase 2: key generation

74. Message policy example
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Attributes
Process instance (case id)

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Phase 3: deciphering

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Phase 3: deciphering

77. Focus
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14548487, Supplier, Mechanics
Why?

78. Q&A
• Why a certifier?
 With signatures, you can prove that “you are you”
 Without a certifier, you cannot prove that what you say is true
• Who forges the keys?
 A delegated key manager
• One certifier, one key manager. What about decentralisation?
 Right…
• Can you integrate your technique with a BPMS?
 Not yet but…
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Marangone, D.C:, Weber: Fine-Grained Data Access Control for Collaborative Process Execution on Blockchain. BPM (Blockchain and RPA Forum) 2022: 51-67

79. Room for improvement
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Marangone, D.C., Friolo, Nemmi, Venturi, Weber: MARTSIA: Enabling Data Confidentiality for Blockchain-based Process Execution (2023)
Multi-Authority Approach to Transaction Systems for Interoperating Applications

80. The new architecture: MARTSIA
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Marangone, D.C., Friolo, Nemmi, Venturi, Weber: MARTSIA: Enabling Data Confidentiality for Blockchain-based Process Execution (2023)
1. Key management 2. Data exchange
0. Initialisation
Push-
inbound
oracle
Pull-
outbound
oracle

81. More expressive policies
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82. More expressive policies
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Only authority A
can release the
decryption key part
that enable
Customs
At least two
authorities are
necessary to forge
the key part of an
actor involved in
case 43175279
Any authority
can generate
the key part
for a
Supplier

83. Room for improvement
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[14] Marangone, D.C., Friolo, Nemmi, Venturi, Weber: MARTSIA: Enabling Data Confidentiality for Blockchain-based Process Execution (2023)
Next: Marangone, D.C., Friolo, Nemmi, Venturi, Weber: Enabling Data Confidentiality with Public Blockchains (2023)
• Who deploys the smart contracts? Does this work only with Ethereum?
 Huh…

84. The attribute certifier should not be a single node!
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Marangone, D.C., Friolo, Nemmi, Venturi, Weber: Enabling Data Confidentiality with Public Blockchains (2023)
2. Init 3. Key management
1. System boot 4. Data exchange

85. Integration with Caterpillar
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86. About the costs
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87. Why are prices in Gwei?
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ETH/EUR exchange Gas price on the Ropsten testnet

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Open challenges
• Revoke access to data
 Check out the InterPlanetary Name System
• Let Smart Contracts use with off-chain data via pull-inbound oracles
• Test with real-world multi-party business processes in production
• Extending the policy language with primitives for aggregating and
manipulating data
• …

89. Look but don’t touch:
On the impalpable bond
between blockchain and
process
Claudio Di Ciccio | claudio.diciccio.net | claudio@diciccio.net
Presented works were funded by the SmartDeFi project, Spoke 09, SERICS (PE00000014), under
the NRRP MUR program funded by the EU – NextGenerationEU; project PINPOINT
(B87G22000450001), under the PRIN MUR program; the Cyber 4.0 project BRIE.