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![Consensus Algorithm
Algorithm to resolve conflicts between nodes.
Bad news: There is no such algorithm [FLP85].
Every protocol has the possibility of non termination,
even with only one faulty node.](https://image.slidesharecdn.com/tezos-summer-school-en-190831121130/85/Blockchain-and-Formal-verification-English-30-320.jpg)
![Block creation
Block proposer (or miner) chooses operations found
in his node and form a block of them.
The validator release to the network.
O1
O1
O2
O2
O2
O2
B = [ O1, O2 ]
→
B
O1
⇨ B1 = [ O1, O2 ]
→
B
B
B
B
B
B
B
B
B = [ , . . , ]Ov1
Ovm
B](https://image.slidesharecdn.com/tezos-summer-school-en-190831121130/85/Blockchain-and-Formal-verification-English-44-320.jpg)
![Ledger Update
Each node updates its state by applying .
where
This forms a “blockchain”:
S B
= ∅S0
= ( ) = ( (. . ( ( )). . ))Sn Bn Sn−1 Bn Bn−1 B1 S0
B(S) = ( (. . ( (S)). . ))Ovm
Ovm−1
O1
B = [ , . . , ]O1 Ovm
. . . .S0 →
B1
S1 →
B2
→
Bn−1
Sn →
Bn](https://image.slidesharecdn.com/tezos-summer-school-en-190831121130/85/Blockchain-and-Formal-verification-English-45-320.jpg)
![Cryptographic Integrity
More precisely, and are digitally signed
to avoid forgery:
where is a raw operation.
where
Digital signing and the hash function are
assumed to be secure.
O B
O = (o, sig (o))nu o
= (b, sig (b))Bn nv b = ([ , . . , ], H( ))Ov1
Ovm
Bn−1
signx H](https://image.slidesharecdn.com/tezos-summer-school-en-190831121130/85/Blockchain-and-Formal-verification-English-46-320.jpg)
![Conflicts
Chain branches when multiple miners propose more
than one blocks:
B = [ O1, O2 ]
→
B
B →
B'
B'
B' = [ O3, O1 ]
B
B'
B B' V'
↗ →
Bn+1
Sn+1 →
Bn+2
Sn+2 →
Bn+3
Sn+3
. . →
Bn−1
Sn−1 →
Bn
Sn
↘ →
B
′
n+1
S
′
n+1
→
B
′
n+2
S
′
n+2
→
B
′
n+3
S
′
n+3](https://image.slidesharecdn.com/tezos-summer-school-en-190831121130/85/Blockchain-and-Formal-verification-English-47-320.jpg)
![The DAO
contract user {
do_deposit()
{
bank.deposit(100);
}
do_withdraw()
{
bank.withdraw();
}
}
contract bank {
deposit()
{
map[SENDER] += AMOUNT;
}
withdraw()
{
send(SENDER, map[SENDER]);
map[SENDER] = 0;
}
}](https://image.slidesharecdn.com/tezos-summer-school-en-190831121130/85/Blockchain-and-Formal-verification-English-87-320.jpg)
![The DAO
contract attack {
do_deposit()
{
bank.deposit(100);
}
do_withdraw()
{
bank.withdraw();
}
default()
{
bank.withdraw();
}
}
contract bank {
deposit()
{
map[SENDER] += AMOUNT;
}
withdraw()
{
send(SENDER, map[SENDER]);
map[SENDER] = 0;
}
}](https://image.slidesharecdn.com/tezos-summer-school-en-190831121130/85/Blockchain-and-Formal-verification-English-88-320.jpg)
![B1 = [ O1, O2 ]
→
B
B
B
B
B
B
B
B
3. The Op. is now in a new block
There is a validator in the sandbox.
Detected the validator took the
operation and made a new block
Bzzz..zzz:
tz1Mawer.. registered in the genesis block is now
activated.
Operation found in block: Bzzz..zzz (pass: 2, offset: 0)
This sequence of operations was run:
Genesis account activation:
Account: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF
Balance updates:
tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ... +ꜩ20000000](https://image.slidesharecdn.com/tezos-summer-school-en-190831121130/85/Blockchain-and-Formal-verification-English-124-320.jpg)
![You cannot steal jun’s token
Since you do not know his secret key:
alice’s secret key is known by tezosclient.
It is stored in .tezoshandsonclient:
$ ./tezosclient transfer 100 from jun to alice ↩
Error:
Unknown secret key for tz1TGu6TN5GSez2ndXXeDX6LgUDvLzPLqgYV
$ cat .tezoshandsonclient/secret_keys ↩
[ { "name": "alice",
"value": "unencrypted:edsk3NDQq5Cmix9H15GkcoVhWo.." } ]](https://image.slidesharecdn.com/tezos-summer-school-en-190831121130/85/Blockchain-and-Formal-verification-English-141-320.jpg)
![Disclaimer
to talented OCaml programmers
CamLIGO is not OCaml.
No recursions: let rec
Type inference is not fully automatic: ([] : int list)
Pattern match is not real pattern match.
No nested patterns: Some (Some x)
No constants in patterns. 1::[]](https://image.slidesharecdn.com/tezos-summer-school-en-190831121130/85/Blockchain-and-Formal-verification-English-151-320.jpg)
![The First CamLIGO Contract
Replace the storage by the parameter string:
Puzzled?
Relax. I do explain.
let main (parameter : string) (storage : string) =
( ([] : operation list), parameter )](https://image.slidesharecdn.com/tezos-summer-school-en-190831121130/85/Blockchain-and-Formal-verification-English-152-320.jpg)
![Function Definition
Arguments must be type-annotated:
(parameter : string)
Arguments are white space separated:
let f (x : ty1) (y : ty2) = ..
❌let f ( (x : ty1), (y : ty2) ) = ..
let function_name (arg1 : type1) ... (argn : typen) =
code
let main (parameter : string) (storage : string) =
( ([] : operation list), parameter )](https://image.slidesharecdn.com/tezos-summer-school-en-190831121130/85/Blockchain-and-Formal-verification-English-153-320.jpg)
![Contract Entrypoint
A function with 2 arguments of:
Parameter: here, parameter
Storage value: here, storage
returns a tuple (..., ...) of:
List of operations: here, empty: [] (with type annotation)
New storage value: here, parameter
let main (parameter : string) (storage : string) =
( ([] : operation list), parameter )](https://image.slidesharecdn.com/tezos-summer-school-en-190831121130/85/Blockchain-and-Formal-verification-English-154-320.jpg)
![Compilation
Place the contract code at contracts/first.mligo
Specify the entrypoint function name main
If you made no mistake, the code should be compiled
down to a Michelson code contracts/first.tz.
$ ./ligo compilecontract contracts/first.mligo main ↩
let main (parameter : string) (storage : string) =
( ([] : operation list), parameter )](https://image.slidesharecdn.com/tezos-summer-school-en-190831121130/85/Blockchain-and-Formal-verification-English-155-320.jpg)
![Smater Contracts: Boomelang
Conditional
if e1 then e2 else e3
Non empty list
[ 1 ; 2 ; 3 ]
Local definition
let v = e1 in e2 Bind the result of e1 to variable v.
let main (param : unit) (storage: unit) =
let ops =
if amount = 0tz then
([] : operation list)
else
[ Operation.transaction () amount
(Operation.get_contract source : unit contract) ]
in
( ops, () )](https://image.slidesharecdn.com/tezos-summer-school-en-190831121130/85/Blockchain-and-Formal-verification-English-171-320.jpg)
More Related Content
Similar to Blockchain and Formal verification (English)
Blockchain and Formal verification (English)
- 1. Blockchain and Smart Contract Verification TezosJapan, DaiLambda, Inc. Jun FURUSE/古瀬淳, Taipei, 2019-08-29FLOLAC’19
- 2. Bit of myself:Past OCaml researcher and programmer Studied type system of FP Like Haskell too FP in Financial Systems Derivative modeling HFT(High Frequency Trading) systems
- 3. Bit of myself:Now NPO to promote Tezos technology in Japan. A small company to participate Tezos core development.
- 4. Bit of Tezos 3rdgen. cryptocurrency (1st: Bitcoin, 2nd: Ethereum, 3rd: many) Consensus algorithm: Proof of Stake On Chain Governance Symbol ꜩ Written in OCaml Formal verification
- 5. Today’s Agenda Brief Historyof Currency What is Blockchain? Technical Aspects of Blockchain Proof of Stake Bit more about Tezos Blockchain and Formal Verification
- 6. Brief History ofCurrency
- 7. Brief History ofCurrency Main theme: “How to trade smoothly?”
- 8.
- 9.
- 10.
- 11. 貝貨 China, 1100 BC 貝貞負貢財貨貫責貪販 貧貶貽賀貲貳貰貸貯貼 買費貿賈賊賃賂賄賑賓 賜質賞賤賠賣賦賚賢賭 購賽賺賻贄贅贇贊贈贏Monetariamoneta Shell has a built-in value (beauty).
- 12. Conditions for Currencies Scaleof value (comparison of values) Means of exchange (easy to carry) Means of store of value (never rotten)
- 13. Coins Mintable: Governments cancontrol the money supply. China, 800 BC (刀貨, 布貨) Coins have built-in values as precious metal. Seigniorage vs counterfait
- 14. Convertible Paper Money Easierto carry Assured conversion to gold (or silver, copper) Total supply is limited to the government’s gold stock ⇄ The medium of the currency has no built-in value. → More strict anti-counterfait requirements
- 15. The First ConvertiblePaper Money 交子in China, around 1050 Started as private notes for iron coins. 宋dynasty assured the conversion between copper coins.
- 16. Credit This is notcurrency, but optimized trade efficiency by recording credit/debt using numbers.
- 17. Fiat Money Inconvertible!「法定通貨」 Since 1971,at the end of . No more support by precious metal, but money stayed as money. Confusions led to floating exchange rate system. Governments can control their money supply. Economy has boosted with more liquidity of currencies. Bretton Woods Agreements
- 18. The First FiatMoney 交子in China, around 1050, again. The world first convertible paper money … and soon became the world first fiat … and lost its value since too many were printed.
- 19. Electronic Money No moremedium. Just numbers in electrons. Pegged with government currencies. Very centralized. Manager companies are responsible for conversion. Cryptography to prevent forgery and cheating.
- 20. The Basis ofthe Value of Currencies Less and less: The value of the medium: Nothing Convertible with precious metal: No The physical form as fiat: No What Makes Money as Money?
- 21. Chartalism Means of payingtax You have to pay tax or you get arrested.
- 22. Radical Theory: CommonKnowledge Common knowledge that it is money. With it, no need of centralized power!! Iraqi Swiss dinar (1993-2003) Somali shillings (1990’s)
- 23. Rise of Cryptocurrencies Since2009-01-03 (Bitcoin): Electronic Decentralized: no central bank Cryptography to prevent counterfait and cheating
- 24. Tracking vs Privacy Electronicmoney made tracking much easier. Powers love tracking. Public do not like being tracked. Nowadays, anonymity is another important condition of currencies. https://twitter.com/maryhui/status/1138675837165641733
- 25.
- 26. What is Blockchain? Let’sforget currency for now: Ledger style DB Distributed Open network Token Smart contracts
- 27. Ledger Style DB DBby history accumulation B1 → B2 → B3 → B4 → .. S0 = ∅ S1 = B1(S0) Sn = Bn(Sn-1) = Bn(Bn-1(..(B1(S0)))) Examples Bankbook Version control system: Git
- 28. Distributed DB Multiple DBnodes, each carries a replica of the DB: Fault tolerance Load balancing
- 29. Distributed DB: conflicts Howto resolve conflicts? B →→ A x = A x = A x = A →→x = B x = B x = A x = B or ? ? ?
- 30. Consensus Algorithm Algorithm toresolve conflicts between nodes. Bad news: There is no such algorithm [FLP85]. Every protocol has the possibility of non termination, even with only one faulty node.
- 31. Good news: Paxos Itmay not terminate, but practically it is OK. Voting between nodes Only for closed network with fixed nodes.
- 32. Closed Network If youare happy with it, you do not need “Blockchain”.
- 33. Open Network Permissionless publicnetwork, where anyone can join with a node. Decentralized, therefore neutral Almost impossible to hack Low cost
- 34. Problem of OpenNetwork Consensus Consensus control and inhibition by Sybil attack: produces fake identities to dominate the network.
- 35. Satoshi Nakamoto andBitcoin Prevent Sybil attacks i.e. infinite identity creations: Requirement of real world resource: computation power (PoW) Rewards: incentive to provide the resource and behave honestly. The rewards are recorded in the DB. Birth of cryptocurrency
- 36. Cryptocurrencies A solution toSybil attacks against open networks.
- 37. Smart Contracts Ledger DBcan carry not only account balance, but any data, even program code. Code attached to an account is executed when it receives a transaction. Automatic execution of financial/non-financial contracts Distributed application (dAPPs) framework, neutral and cost efficient without requirement of central DB managers.
- 38. Gas cost Smart contractscannot run infinitely. To prevent DoS attacks, the caller must pay the running cost to the miner: Gas limit, out of gas Contract calls fail if its runtime cost exceeds the declared gas cost or the system gas limit. VM model To calculate the gas cost, smart contract language is often implemented as a VM.
- 39. What is Blockchain LedgerDB Distributed Open network Token for incentives Smart contracts
- 40.
- 41. Blockchain Network P2P networkwith multiple nodes, each has a replica of the ledger DB.
- 42. Reading from theDB Query past / current state of the ledger to a node. ! ? → ? ! →
- 43. Writing to theDB Sending operation to a node: Transactions Account creations, etc Operations spread into the P2P network. → → O1 O1 O1 O1 O1 O1 O2 O2 O2 O2 O2 O2 O2 O2 O
- 44. Block creation Block proposer(or miner) chooses operations found in his node and form a block of them. The validator release to the network. O1 O1 O2 O2 O2 O2 B = [ O1, O2 ] → B O1 ⇨ B1 = [ O1, O2 ] → B B B B B B B B B = [ , . . , ]Ov1 Ovm B
- 45. Ledger Update Each nodeupdates its state by applying . where This forms a “blockchain”: S B = ∅S0 = ( ) = ( (. . ( ( )). . ))Sn Bn Sn−1 Bn Bn−1 B1 S0 B(S) = ( (. . ( (S)). . ))Ovm Ovm−1 O1 B = [ , . . , ]O1 Ovm . . . .S0 → B1 S1 → B2 → Bn−1 Sn → Bn
- 46. Cryptographic Integrity More precisely,and are digitally signed to avoid forgery: where is a raw operation. where Digital signing and the hash function are assumed to be secure. O B O = (o, sig (o))nu o = (b, sig (b))Bn nv b = ([ , . . , ], H( ))Ov1 Ovm Bn−1 signx H
- 47. Conflicts Chain branches whenmultiple miners propose more than one blocks: B = [ O1, O2 ] → B B → B' B' B' = [ O3, O1 ] B B' B B' V' ↗ → Bn+1 Sn+1 → Bn+2 Sn+2 → Bn+3 Sn+3 . . → Bn−1 Sn−1 → Bn Sn ↘ → B ′ n+1 S ′ n+1 → B ′ n+2 S ′ n+2 → B ′ n+3 S ′ n+3
- 48. Attack: Double Spending Youcan steal exchanging tokens in the both branches: ↗ ↗ → Bn+1 Sn+1 → Bn+2 Sn+2 → Bn+3 Sn+3 . . → Bn−1 Sn−1 → Bn Sn ↘ → B ′ n+1 S ′ n+1 → B ′ n+2 S ′ n+2 → B ′ n+3 S ′ n+3 ↘
- 49. Proof of Work(PoW) Blocks must be with an answer to a hash puzzle : is generated from . is a weak hash function. The nodes choose the longer chain, which used more computation power (or gathered votes): Q = ( , sig ( ), ) where ( ) =Bn bn nv bn An H ′ An Qn Qn bn (⋅)H ′ . . → Bn Sn → Bn+1 Sn+1 → Bn+2 Sn+2 → Bn+3 Sn+3 → Bn+4 Sn+4 ↘ B ′ n+1 S ′ n+1 → B ′ n+2 S ′ n+2
- 50. Incentivize Miners The costof solving hash puzzles is covered by rewards. Block reward , newly minted. Transaction fee: in , set and paid by the issuer of By proposing a block , the validator can earn r f o = (raw operation, f ) o B r + Σo∈B fo
- 51. Nakamoto Consensus Rewards areonly available in the branch. No incentive to bet on shorter branches. Longer branches might be overridden by shorter ones, but the probability decreases exponentially as it grows. User sends tokens to Exchange at to change them to USD. Exchange pays out the USD after to User in return, when it is sure cannot be taken over. . . → . . →. .Sn−1 → Bn Sn → Bn+1 Sn+1 → Bn+2 → Bn+6 Sn+6 Bn Bn+6 Bn
- 52. 51% Attack Someone withmore than 50% of computation power can take over the chain to perform double spending. ⬇ . . → . .Sn−1 → Bn Sn → Bn+1 → Bn+6 Sn+6 . . → . .Sn−1 → Bn Sn → Bn+1 → Bn+6 Sn+6 ↘ . .S ′ n−1 → B ′ n S ′ n → B ′ n+1 → B ′ n+6 S ′ n+6 → B ′ n+7 S ′ n+7 → B ′ n+8 S ′ n+8
- 53. 51% Attacks areReal Minor PoW blockchains, which requires less hash power, are targets of 51% attacks: Verge (XVG), 2M USD (2018-04 and 2018-05) Bitcoin Gold (BTG), 18M USD (2018-05) Monacoin (MONA), 90K USD (2018-05) ZenCash (ZEN) 700K USD (2018-06)
- 54. Blockchain: Technical Details TypicalPoW Operation injection Block creation of operations, and upload Ledger update by blocks Branching by conflicts PoW to reduce and choose branches 51% attacks
- 55. Proof of Stakeand Tezos
- 56. PoW is EnergyInefficient Bitcoin uses 73.12T Wh to maintain its network per year. Which is 3.6B USD/y. Equivalent with the electricity consumption of Austria. Equivalent with the consumption of 6.7M households in US. https://digiconomist.net/bitcoin-energy-consumption
- 57. Risk of Centralization Minerstend to concentrate: PoW is less profitable in regions with higher electricity fee. Concentration of mining powers, i.e. mining pools, makes PoW more efficient. Centralization damages the network security.
- 58. Incentive Misalignment ofPoW Stakeholders and miners are largely different, and their incentives are different. Most of the token owners are not miners, miners are not obliged to keep their positions in PoW. Miners want to maximize their mining rewards. This may work against the interests of token owners.
- 59. Proof of Stake(PoS) PoS: Another Solution to Sybil Attack: Block mining right based not on computation power but on the stake (how much you have) The past stake in the DB is fixed. Sybil attack is prevented. Mining right is assigned only to long-term stakeholders. 51% attack is still possible, but you need to own half of the token supply for enough long.
- 60. Raspberry PI 3,2watts for Tezos PoS: Eco-Friendly + Decentralization No competition of solving puzzles: Mining → “Baking” No special hardware required: No concentration for efficiency required. Antminer S9, 1350watts for Bitcoin
- 61. PoS: Aligned Incentives Miners⊂ Stakeholders You have to hold your position long enough to participate the consensus. Mining right is delegatable. You can participate the network by delegating your right to get some of rewards, not risking your stake.
- 62. Possible Attacks toPoS Double spending by branching with past stake: Nothing at stake attacks Long range attacks Exchange the stake with goods ⤴ → → → → → ↘ Branch using the past stake → → → → → Make the above chain inactive
- 63. Tezos Consensus Countermeasures againstthe attacks. For nothing at stake attacks Endorsement Security deposit For nothing at stake attack Checkpoints
- 64. Endorsement Based on NakamotoConsensus with endorsement. For each block level , 32 endorsers are chosen: Each endorse one block of and sign. Branches with more endorsements win. The attacker must control much more accounts. i Bij , . . ,Bi1 Bin . . → . .Sn−1 → Bn Sn → Bn+1 → Bn+6 Sn+6 ↘ . .S ′ n−1 → B ′ n S ′ n → B ′ n+1 → B ′ n+6 S ′ n+6 → B ′ n+7 S ′ n+7 → B ′ n+8 S ′ n+8
- 65. Security Deposit Security depositfor mining and endorsement. Branching attempt is punished by slashing the deposit and rewards. Double minings/endorsements in the same level Deposit is returned when reorg becomes impossible (15 days) ↕ Branching attempt by the same validator is punished. . . . .→ Bn−1 Sn−1 → Bn Sn → Bn+1 Sn+1 → Bn+2 . .↘ B ′ n+1 S ′ n+1 → B ′ n+2
- 66. Checkpoints Record block hashesperiodically outside of the chain: H(B) https://www.news.com Tezos’s block hash at is , BKveMfA..n H( )Bn . . → S →. . →. . →. . →. . →. . →. . → S→ Bn Sn . . →. . →. . →. . →. . →. . →↘ → B ′ n S ′ n S ″
- 67. PoS and Tezos PoWhas energy inefficiency and incentive unalignment PoS: Mining right proportional to the stake against Sybil attack Eco friendly Incentive is aligned Attack against PoS: Branching by past stake and solutions in Tezos (and other protocols): Endorsements Security deposit to prevent intentional branching Checkpoints
- 68.
- 69. Other Tezos Highlights Basicphilosophy Liquid PoS On chain governance Formal verification
- 70. Philosophy of Tezos Blockchainprotocol for stakeholders Safety is the first priority
- 71. (Virtual) Pure PoS Allthe stakeholders can propose blocks. Direct democracy. Problem: it does not scale: Not all stakeholders can run mining facilities 27h/7d Slowed down for waiting stakeholders without mining facilities
- 72. Delegated PoS Blocks areproposed only by small num of delegates. Stakeholders can vote to select delegates. Indirect democracy. Pros: Highly efficient thanks to the small number of miners. ex. EOS: 21 super nodes. Stakeholders can receive rewards via voting. Easier to implement consensus algorithm like PBFT. Cons: Network get centralized: less secure.
- 73. Liquid PoS (Tezos) Allthe stakeholders can propose blocks, or they may delegate their rights to other miners. “Protocol is owned not only by selected validators, but by all the stakeholders.” Unlimited number of validators: ex. Tezos: 500 bakers Slower than DPoS but more decentralized i.e. securer. Stakeholders can receive rewards through delegation.
- 74.
- 75. Tezos and OnChain Governance
- 76. What is Governancein Blockchain “How to fork (upgrade) protocols?” Soft/Hard fork Soft fork Backward compatible Hard fork Backward incompatible: Past valid blocks may become invalid under the new protocol.
- 77. Risk of HardFork A hard fork of a protocol may cause a hard fork of the community. Ethereum and Ethereum Classic hard fork after DAO incident Hard fork of Bitcoin Cash and “hash war” Goal of the Governance Smooth evolution of blockchain protocol without community hard fork.
- 78. On Chain Governance Protocolupgrade is implemented in protocol itself, and all the processes are recorded on chain: Protocol upgrade proposal Test of proposal Vote to upgrade Automatic upgrade of nodes Protocol defines how itself is to be upgraded. “Protocol is owned not by developers but by stakeholders.”
- 79. Tezos: Protocol Separation Definethe target of on chain governance: Shell Network, storage, etc. Not the target, since their change only cause soft forks. Protocol Semantics of transactions and how to reach consensus. The target of on chain governance, since their change triggers hard fork.
- 80. Tezos: On ChainGovernance 90 day cycle of governance: Code of proposals uploaded First vote: select one of them Second vote: test it or not Test phase Final vote: upgrade or not Automatic node upgrade Liquid democracy voting right is weighted by stakes, and delegatable just like LPoS.
- 81. Tezos: Governance History “Athens”:Tezos’s first protocol upgrade. Just changes of few constant parameters. 2019-05-21: Passed the final vote 2019-05-30: Activated “Babylon”: and others. 2019-08-29: Passed the first 2 votes. Now in the test phase Improved consensus algorithm
- 82. Other Tezos Highlights Basicphilosophy Liquid PoS On chain governance Formal verification ← Coming soon
- 83.
- 84. What is Blockchain(again) Ledger DB Distributed Open network Token for incentives Smart contracts
- 85. Safety Requirements ofBlockchain As a consequence of introduction of token rewards for open distributed DB: Speculative money flows in. System must be open source. Security holes are immediate targets for theft. Blockchain must have very high level of security.
- 86. Safety of SmartContracts Smart contracts must be also very secure. Past incidents around smart contracts: The DAO (3.6M ETH, 15% of circulation, 50M USD stolen) Parity vulnerability#1 (150K ETH, 32M USD stolen) Parity vulnerability#2 (513K ETH, 160M USD frozen) High level of security is required here too.
- 87. The DAO contract user{ do_deposit() { bank.deposit(100); } do_withdraw() { bank.withdraw(); } } contract bank { deposit() { map[SENDER] += AMOUNT; } withdraw() { send(SENDER, map[SENDER]); map[SENDER] = 0; } }
- 88. The DAO contract attack{ do_deposit() { bank.deposit(100); } do_withdraw() { bank.withdraw(); } default() { bank.withdraw(); } } contract bank { deposit() { map[SENDER] += AMOUNT; } withdraw() { send(SENDER, map[SENDER]); map[SENDER] = 0; } }
- 89. Blockchain is aBig Pile of Components Protocol: consensus, incentive design, transaction semantics Smart contract: semantics, compiler Cryptographic algorithms P2P networking Storage All of these components must be secure.
- 90. How to SecureBlockchain Test Important but not enough. Formal verification The way to go.
- 91. Software Test Run asystem under given conditions to see everything goes fine. Run and see, then repeat. Easy. Testable only few corner cases No guarantee for the untested cases.
- 92. Formal Verification Mathematically proveprograms have good/bad properties. Property is assured for all the cases, if proven. Proving is generally much harder than tests.
- 93. Formal Verification Methods Statictyping Model checking Theorem proving
- 94. Static Type Checking Expressproperties of values and expressions in types. Restrict program compositions to those typable, to assure the properties hold for the entire program. Pros: automatic if type inference is available. Cons: relatively weak expressive power.
- 95. Model Checking Abstract aprogram to a finite state transition system, then check it satisfies the properties we want. Pros: automatic. A counterexample is given at failure. Cons: Hard to provide a good modeling.
- 96. Theorem Proving Prove theproperty of program directly, using proof assistant such as Coq: Pros: most powerful Cons: Writing a proof can be very hard.
- 97. Formal Verification forBlockchain Formal verification is used for critical systems such as: Aerospace industry Nuclear plants Blockchain is also a critical system. It must be formally verified. It is also an ideal target of formal verification: No hardware. Open source. Smart contract is a programming language.
- 98. Tezos and FormalVerification Statically typed smart contracts both at VM and high level language levels Modeling of smart contract interpreter using Coq, and correctness proofs of smart contracts using it. Correctness of cryptographic primitives Incoming: Correctness proof of sparse Merkle tree storage using F*. Certified compiler of smart contracts. etc.
- 99. Michelson: Tezos SmartContract VM Stack VM Purely functional: no side effects No mutable variables Transactions are not side effects. Re-entrancy bug is impossible. With strong static typing No runtime type mismatch like "hello" + 10 Different numeric types for currency, , , ꜩ. Arbitrary precision and . No overflow / underflow VM level data structures: Lists, sets, maps, options ℕ ℤ ℕ ℤ
- 100. Michelson interpreter Implements thesemantics of Michelson in node: Purely functional: no side effects Secured by GADTs (Guarded Algebraic Data Types) VM state (code and stack) construction is assured well-typed in the VM type system. Evaluation (state-to-state transition) preserves the well- typedness.
- 101. Mi-Cho-Coq: VM modelingin Coq Michelson is reimplemented in Coq proof assistant. Provides framework to prove correctness around Michelson. Found documentation bugs in the specification. https://gitlab.com/nomadic-labs/mi-cho-coq/
- 102. Smart Contract CorrectnessProofs Using Mi-Cho-Coq. 例: An operation to the account is performed only when enough number of signatures of registered users are attached. multi-sig contract https://gitlab.com/nomadic-labs/mi-cho-coq/blob/master/src/contracts_coq/multisig.v
- 103. HACL*: Verified Cryptography Formallyverified cryptographic functions in F*. ChaCha20, Salsa20, HMAC, SHA-256, SHA-512, Ed25519, etc. F* compiles down to fast C code. Properties proved: Memory safety Correctness of the algorithm Secret independence: immune to the side channel attacks https://github.com/project-everest/hacl-star
- 104. F* Functional language withrefinement types, developed by Microsoft: Compatible syntax with OCaml Some verifications can be done automatically by Z3 Extraction to OCaml, F#, C, WASM, ASM https://www.fstar-lang.org/
- 105. On Going Projects Theyare just I know so far: Sparse Merkle tree for storage. The correctness of tree operations will be verified by F* Certified compiler of smart contract Prove the correctness of compilation from higher level language to Michelson DSL for contracts in Tezos. Verification using deductive program verification platform. Plebeia Archetype Why3
- 106. Tezos and FormalVerification Blockchain is a critical system. Test is important, but FV is also required. All components should be verified. Tezos is a very good target to perform FV.
- 107.
- 108. Calicurum Preparation Docker images install Gitrepository Basic transaction Try tezosclient Account creation Token transactions Introduction to smart contract Basic concepts of Tezos smart contracts compiler Contract compilation, deploy, and call LIGO
- 109.
- 110. Prep #1: Dockerand images Install Linux users: configure so that you can run docker command without sudo: ( ) Install 2 docker images Check images are working: Docker details $ docker pull dailambda/tezoshandson:201908 ↩ $ docker pull dailambda/ligo:201908 ↩ $ docker run dailambda/tezoshandson:201908 ↩ hello tezos $ docker run dailambda/ligo:201908 ↩ hello tezos
- 111. Prep #2: CloneGit repository Contents tezoshandsonnode A sandboxed node for hands-on tezosclient . You can do everything with it. ligo compiler contracts/ Camligo contract samples $ git clone https://gitlab.com/dailambda/dockertezoshandson b tezoshandson201908 ↩ $ cd dockertezoshandson ↩ Command line wallet LIGO
- 112. If you darewant to build Docker images… Sources are available in dockernode/ and dockerligo/ of the repo.
- 113.
- 114. Usual Tezos Development… Weusually start a Tezos node connecting to the test network called “Alpha net”: ↪↪ Tezos Network But it takes time to sync your node to the network…
- 115. Today, We UseSandbox ↪↪ Closed in your computuer. No external net access required. No need to sync with the test/main network. No need to buy real Tezos tokens. You can reset the environment easily.
- 116. Sandboxed Environment forHands-on Let’s start it: and keep it running. Note: The node uses TCP port 18732. Reset, if something goes wrong: $ ./tezoshandsonnode ↩ # Stop tezoshandsonnode, then $ rm rf .tezoshandsonnode .tezoshandsonclient ↩ $ ./tezoshandsonnode
- 117.
- 118. Check it isworking Open a new terminal, then: $ ./tezosclient bootstrapped ↩ Current head: BLNeoW9n94mD (timestamp: .. Bootstrapped.
- 119. ICO Commitments Tezos fundraiserdonors receive commitment information to activate their Tezos accounts in Mainnet. In this hands-on, 2 dummy commitment files are prepared: $ ls commitments/ tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF.json tz1X4maqF9tC1Yn4jULjHRAyzjAtc25Z68TX.json
- 120. Account Activation Careful oftypo. tz1xx..xx is the name (public key hash) of the account. alice is an alias, which you can choose what ever you want. It may take several ten seconds. $ ./tezosclient activate account alice with commitments/tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF.json ↩ .. Operation successfully injected in the node. .. The operation has only been included 0 blocks ago. .. Account alice (tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF) activated with ꜩ27182818.28459.
- 121. What Happend?! I doexplain. $ ./tezosclient activate account alice with commitments/tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF.json Node is bootstrapped, ready for injecting operations. Operation successfully injected in the node. Operation hash is 'oo6rb94mw9Z4rKexQhYDnSZeXXWmcZ65vcz77KTDTcGstYYeeuC' Waiting for the operation to be included... Operation found in block: BKqArov5fNKzptY81CLsacSTTPh7tPmCXoqeQ4pNzKCP6GtGiro (pass: 2, offset: 0) This sequence of operations was run: Genesis account activation: Account: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF Balance updates: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ... +ꜩ20000000
- 122. 1. Check theconnected node The node must be well sync’ed with the network: The sandbox is always bootstrapped, so no problem. Node is bootstrapped, ready for injecting operations.
- 123. → → O1 O1 O1 O1 O1 O1 O2 O2 O2 O2 O2 O2 O2 O2 2. Inject theoperation to the network Operation ooyyy..yyy for the account activation was injected to the network: Waiting the operation is taken for a new block. Operation successfully injected in the node. Operation hash is 'ooyyy..yyy' Waiting for the operation to be included...
- 124. B1 = [ O1, O2 ] → B B B B B B B B 3. The Op.is now in a new block There is a validator in the sandbox. Detected the validator took the operation and made a new block Bzzz..zzz: tz1Mawer.. registered in the genesis block is now activated. Operation found in block: Bzzz..zzz (pass: 2, offset: 0) This sequence of operations was run: Genesis account activation: Account: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF Balance updates: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ... +ꜩ20000000
- 125. 4. You maywait for more blocks. The block may be still overridden by the consensus. Under Nakamoto consensus, longer you wait, the certainity incrases exponentially. In this hands-on, there is no point to wait. The operation has only been included 0 blocks ago. We recommend to wait more. Use command tezosclient wait for oo6rb94mw9Z4rKexQhYDnSZeXXWmcZ65vcz77KTDTcGstYYeeuC to be included confirmations 30 branch BL26XEjqN4uKAnEC52z6ijj3XibpbcM4ysPLUfcJqkMccyHriV3 and/or an external block explorer. Account alice (tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF) activated with ꜩ20000000.
- 126. Operation Processing inTezos The same as we saw for the activation: Make an operation. Upload the operation to the P2P network. A validator makes a block with the operation. The block is uploaded to the P2P network. The certainity of the operation increases as the chain grows.
- 127.
- 128. How much doI have? Ask the blockchain: alice is an alias of tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF. Therefore, $ ./tezosclient get balance for alice ↩ 20000000 ꜩ $ ./tezosclient get balance for tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ↩ 20000000 ꜩ
- 129. Balance of theothers Tezos accounts are not anonymous. You can check the balance of other’s. For example, tz1TGu6TN5GSez2ndXXeDX6LgUDvLzPLqgYV: Hard to type? The account name is found in file accounts.txt: $ ./tezosclient get balance for tz1TGu6TN5GSez2ndXXeDX6LgUDvLzPLqgYV ↩ 0.000001 ꜩ $ cat accounts.txt ↩ tz1TGu6TN5GSez2ndXXeDX6LgUDvLzPLqgYV
- 130. Account Alias You cangive an alias to an account: $ ./tezosclient add address jun tz1TGu6TN5GSez2ndXXeDX6LgUDvLzPLqgYV ↩ $ ./tezosclient get balance for jun ↩ 0.000001 ꜩ
- 131. Accounts known bytezosclient alice’s secret key (sk) is known. It is your account. jun’s secret key is not available. It is not yours. Keep your secret key secret!! Once known, your account is owned by others. $ ./tezosclient list known addresses ↩ jun: tz1TGu6TN5GSez2ndXXeDX6LgUDvLzPLq.. alice: tz1MawerETND6bqJqx8GV3YHUrvMBCD.. (unencrypted sk known)
- 132.
- 133. Send some tojun Thanks! It prints lots: I do explain. $ ./tezosclient transfer 100 from alice to jun ↩ $ ./tezosclient transfer 100 from alice to jun ↩ Node is bootstrapped, ready for injecting operations. Estimated gas: 10200 units (will add 100 for safety) Estimated storage: no bytes added Operation successfully injected in the node. Operation hash is 'ooJZ1U114ibPfikZNrDSfmqg8Tcs9CzshL4w1vvsDa35DdB72bN' Waiting for the operation to be included... Operation found in block: BL6H8145DMyPeXBQBc2JPRKpVstJSYkhgyGSFFhEJQGAfYweQ8u (pass: 3, offset: 0) This sequence of operations was run: Manager signed operations: From: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF Fee to the baker: ꜩ0.001258 Expected counter: 1 Gas limit: 10000 Storage limit: 0 bytes Balance updates: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ........... ꜩ0.001258 fees(tz1ddb9NMYHZi5UzPdzTZMYQQZoMub195zgv,6) ... +ꜩ0.001258 Revelation of manager public key: Contract: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF Key: edpkuSR6ywqsk17myFVRcw2eXhVib2MeLc9D1QkEQb98ctWUBwSJpF This revelation was successfully applied Consumed gas: 10000 Manager signed operations: From: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF Fee to the baker: ꜩ0.001186 Expected counter: 2 Gas limit: 10300 Storage limit: 0 bytes Balance updates: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ........... ꜩ0.001186 fees(tz1ddb9NMYHZi5UzPdzTZMYQQZoMub195zgv,6) ... +ꜩ0.001186 Transaction: Amount: ꜩ100 From: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF To: tz1TGu6TN5GSez2ndXXeDX6LgUDvLzPLqgYV This transaction was successfully applied Consumed gas: 10200 Balance updates: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ... ꜩ100 tz1TGu6TN5GSez2ndXXeDX6LgUDvLzPLqgYV ... +ꜩ100 The operation has only been included 0 blocks ago. We recommend to wait more. Use command tezosclient wait for ooJZ1U114ibPfikZNrDSfmqg8Tcs9CzshL4w1vvsDa35DdB72bN to be included confirmations 30 branch BLpBxE6wFBQcvNPyUg7sdodpZN3Xra2qGAAJXPG7Z7i9EM94ivj and/or an external block explorer.
- 134. 1. Check theconnected node Waiting for the node to be bootstrapped before injection... Current head: BL.. (timestamp: .., validation: ..) Node is bootstrapped, ready for injecting operations.
- 135. 2. Gas estimation and operation injection Estimated gas: 10200 units (will add 100 for safety) Estimated storage: no bytes added Operation successfully injected in the node. Operation hash is 'oOOO..OOO' Waiting for the operation to be included...
- 136. 3. The operationis now in a new block Let’s see more details here. Operation found in block: BL6H8145DMyPeXBQBc2JPRKpVstJSYkhgyGSFFhEJQGAfYweQ8u (pass: 3, offset: 0) This sequence of operations was run: Manager signed operations: From: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF Fee to the baker: ꜩ0.001258 Expected counter: 1 Gas limit: 10000 Storage limit: 0 bytes Balance updates: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ........... ꜩ0.001258 fees(tz1ddb9NMYHZi5UzPdzTZMYQQZoMub195zgv,6) ... +ꜩ0.001258 Revelation of manager public key: Contract: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF Key: edpkuSR6ywqsk17myFVRcw2eXhVib2MeLc9D1QkEQb98ctWUBwSJpF This revelation was successfully applied Consumed gas: 10000 Manager signed operations: From: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF Fee to the baker: ꜩ0.001186 Expected counter: 2 Gas limit: 10300 Storage limit: 0 bytes Balance updates: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ........... ꜩ0.001186 fees(tz1ddb9NMYHZi5UzPdzTZMYQQZoMub195zgv,6) ... +ꜩ0.001186 Transaction: Amount: ꜩ100 From: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF To: tz1TGu6TN5GSez2ndXXeDX6LgUDvLzPLqgYV This transaction was successfully applied Consumed gas: 10200
- 137. 3.1 Revealation thepublic key The public key edpkuSR6ywqsk.. of alice must be revealed to the blockchain, so that others can verify alice’s operation with it: Manager signed operations: From: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF Fee to the baker: ꜩ0.001258 Fee to the validator Expected counter: 1 Gas limit: 10000 Storage limit: 0 bytes Balance updates: Fee is paid to the validator. tz1MawerETND6bqJqx8GV3YHUrvM ........... ꜩ0.001258 fees(tz1ddb9NMYHZi5UzPdzTZMY95zgv,6) ... +ꜩ0.001258 Revelation of manager public key: Contract: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF Key: edpkuSR6ywqsk17myFVRcw2eXhVib2MeLc9D1QkEQb98.. This revelation was successfully applied Consumed gas: 10000
- 138. 3.2 The transaction Manager signed operations: From: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF Fee to the baker: ꜩ0.001186 Fee to the validator Expected counter: 2 Gas limit: 10300 Storage limit: 0 bytes Balance updates: Fee is paid to the validator. tz1MawerETND6bqJqx8GV3YHUrvM ........... ꜩ0.001186 fees(tz1ddb9NMYHZi5UzPdzTZMY..zgv,6) ... +ꜩ0.001186 Transaction: Amount: ꜩ100 The amount of the transaction From: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF To: tz1TGu6TN5GSez2ndXXeDX6LgUDvLzPLqgYV This transaction was successfully applied Consumed gas: 10200 Balance updates: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ... ꜩ100 alice pays tz1TGu6TN5GSez2ndXXeDX6LgUDvLzPLqgYV ... +ꜩ100 to jun
- 139. 4. You maywait for more blocks. The operation has only been included 0 blocks ago. We recommend to wait more. Use command tezosclient wait for ooZZZ..ZZZ to be included confirmations 30 branch B.. and/or an external block explorer.
- 140. Check the balance Thetoken was really transferred? Check it: The balance of alice should decrease by 100tz + the fee paid for the validator. $ ./tezosclient get balance for alice ↩ 19999899.997556 ꜩ $ ./tezosclient get balance for jun ↩ 100.000001 ꜩ
- 141. You cannot stealjun’s token Since you do not know his secret key: alice’s secret key is known by tezosclient. It is stored in .tezoshandsonclient: $ ./tezosclient transfer 100 from jun to alice ↩ Error: Unknown secret key for tz1TGu6TN5GSez2ndXXeDX6LgUDvLzPLqgYV $ cat .tezoshandsonclient/secret_keys ↩ [ { "name": "alice", "value": "unencrypted:edsk3NDQq5Cmix9H15GkcoVhWo.." } ]
- 142. Gas, Storage, andFee of Tezos Who wants to issue opreations in Tezos must propose: Cost Estimation Gas limit How much CPU power is required. Storage limit How much additional storage is required. Incentive to the validator Fee Paid by the issuer to the validator, if the op. is taken into the new block.
- 143. What Validator Does Comparethe cost estimation and the fee: Fee > Cost estimation Take the operation into the new block to receive the fee. Cost estimation > Fee Operation will not be used for the new block. Operation issuer should: Propose proper fee Operations with too low fee are never taken into the blockchain. Should not cheat the validator with too low cost estimate The operation fails and the fee is taken by the validator, if actual operation cost exceeds the estimate.
- 144. Build your newaccount Create a pair of secret and public keys. Easy: $ ./tezosclient gen keys alice2 $ ./tezosclient list known addresses alice2: tz1M9ZZccgEAgtDGMu8R7xniFt.. (unencrypted sk known) jun: tz1TGu6TN5GSez2ndXXeDX6LgUDvLzPLqgYV alice: tz1MawerETND6bqJqx8GV3YHUrv.. (unencrypted sk known)
- 145. Burn: fee toadd storage Sending from alice to alice2 10000ꜩ fails: Additional storage is required to record the new account to the blockchain. 0.257ꜩ is required to burn. $ ./tezosclient transfer 10000 from alice to alice2 Fatal error: The operation will burn ꜩ0.257 which is higher than the configured burn cap (ꜩ0). Use `burncap 0.257` to emit this operation. Exiting $ ./tezosclient transfer 10000 from alice to alice2 burncap 0.257 ... Balance updates: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ... ꜩ10000 tz1cMEsG9mvL8zyiGHppcCjcz1Et65zwidfg ... +ꜩ10000 tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ... ꜩ0.257 Burn
- 146.
- 147. How Tezos SmartContracts Work Accounts KTxxx..xxx can have smart contracts. Contract state Balance Code Persistent storage Trigger Code is executed at each transaction to the contract.
- 148. Tezos Contract isPure Function Input Parameter given at the transaction. Storage contents Global constants (current account balance, amount of the transaction, the source of the transaction, etc) Output Operations (transactions, call of other smart contracts, etc.) New storage contents No side effects Immutable. Purely functional.
- 149. Michelson for Tezos smartcontracts, and its language. VM but high level: Statically typed , with arbitrary precision. No overflow. Data types (options, lists, sets, map) Cryptographic primitives But bit hard to read and write… Stack VM # Return to the source parameter unit; storage unit; code { CDR ; NIL operation ; AMOUNT; PUSH mutez 0; IFCMPEQ { } { SOURCE ; CONTRACT unit ; ASSERT_SOME ; AMOUNT ; UNIT ; TRANSFER_TOKENS ; CONS ; }; PAIR; } ℕ ℤ
- 150. CameLIGO Today, we use highlevel language for Tezos smart contracts. Compiler LIGO code is compiled down to Michelson 2 syntaxes PascaLIGO (Pascal like) and CamLIGO (OCaml like) Cheat sheet and samples Samples are under ./contracts Still very new and glitchy, but already usable. LIGO(http://ligolang.org) https://gitlab.com/dailambda/mligo_contracts/blob/master/cheat-sheet.md
- 151. Disclaimer to talented OCamlprogrammers CamLIGO is not OCaml. No recursions: let rec Type inference is not fully automatic: ([] : int list) Pattern match is not real pattern match. No nested patterns: Some (Some x) No constants in patterns. 1::[]
- 152. The First CamLIGOContract Replace the storage by the parameter string: Puzzled? Relax. I do explain. let main (parameter : string) (storage : string) = ( ([] : operation list), parameter )
- 153. Function Definition Arguments mustbe type-annotated: (parameter : string) Arguments are white space separated: let f (x : ty1) (y : ty2) = .. ❌let f ( (x : ty1), (y : ty2) ) = .. let function_name (arg1 : type1) ... (argn : typen) = code let main (parameter : string) (storage : string) = ( ([] : operation list), parameter )
- 154. Contract Entrypoint A functionwith 2 arguments of: Parameter: here, parameter Storage value: here, storage returns a tuple (..., ...) of: List of operations: here, empty: [] (with type annotation) New storage value: here, parameter let main (parameter : string) (storage : string) = ( ([] : operation list), parameter )
- 155. Compilation Place the contractcode at contracts/first.mligo Specify the entrypoint function name main If you made no mistake, the code should be compiled down to a Michelson code contracts/first.tz. $ ./ligo compilecontract contracts/first.mligo main ↩ let main (parameter : string) (storage : string) = ( ([] : operation list), parameter )
- 156. Look of MichelsonCode Puzzled? No worry, I do not explain. { parameter string ; storage string ; code { {} ; { { { { DUP } ; CAR } ; { { { { DIP { DUP } ; SWAP } } ; CDR } ; { { { DIP { DUP } ; SWAP } ; NIL operation } ; PAIR } ; {} ; DIP { { DIP { DIP { DIP { {} } } } ; DROP } } } ; {} ; DIP { { DIP { DIP { {} } } ; DROP } } } ; DIP { { DIP { {} } ; DROP } } } } }
- 157. Contract Deployment first: Aliasof the contract for alice: Manager is alice transferring 0 from alice: Initial balance is 0 paid by alice running contracts/first.tz: The Michelson code init '"initial value"': The initial storage value burncap 0.506: For registration network fee $ ./tezosclient originate contract first for alice transferring 0 from alice running contracts/first.tz init '"initial value"' burncap 0.506 ↩
- 158. Did not workfor you? Few things you should check: Check typo Your account alias is alice? Quotes are important: '"initial value"' Got "Error: At line 1 character 0, blahblah Limitation of Docker. Please place first.tz under the directory with ligo. Got “Fatal error” about the burn cap? Asked more? Longer initial storage string costs you more.
- 159. If you aresuccessful I do explain. $ ./tezosclient originate contract first for alice transferring 0 from alice running contracts/first.tz init '"initial value"' burncap 0.506 ↩ Node is bootstrapped, ready for injecting operations. Estimated gas: 16275 units (will add 100 for safety) Estimated storage: 506 bytes added (will add 20 for safety) Operation successfully injected in the node. Operation hash is 'ooe54u2xReWTmbV6eWeKZf3SbWNRMGcFdyuVKDU5UpjYtM1EVDU' Waiting for the operation to be included... Operation found in block: BLCmgqwqMShuD38WYFabrD8o8XRf9Xp7W5ZyUkjQYYiK7ULF8qv (pass: 3, offset: 0) This sequence of operations was run: Manager signed operations: From: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF Fee to the baker: ꜩ0.002139 Expected counter: 3 Gas limit: 16375 Storage limit: 526 bytes Balance updates: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ............ ꜩ0.002139 fees(tz1ddb9NMYHZi5UzPdzTZMYQQZoMub195zgv,10) ... +ꜩ0.002139 Origination: From: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF For: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF Credit: ꜩ0 Script: { parameter string ; storage string ; code { {} ; { { { DUP ; CAR } ; { { { DUUP } ; CDR } ; { { DUUP ; NIL operation } ; PAIR } ; {} ; DIP { { DIP { DIP { DIP { {} } } } ; DROP } } } ; {} ; DIP { { DIP { DIP { {} } } ; DROP } } } ; DIP { { DIP { {} } ; DROP } } } } } Initial storage: "initial value" No delegate for this contract This origination was successfully applied Originated contracts: KT1NmLBEGeKrppHESUK9KEkHjj6i4677J3cS Storage size: 249 bytes Paid storage size diff: 249 bytes Consumed gas: 16275 Balance updates: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ... ꜩ0.249 tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ... ꜩ0.257 New contract KT1NmLBEGeKrppHESUK9KEkHjj6i4677J3cS originated. The operation has only been included 0 blocks ago. We recommend to wait more. Use command tezosclient wait for ooe54u2xReWTmbV6eWeKZf3SbWNRMGcFdyuVKDU5UpjYtM1EVDU to be included confirmations 30 branch BLTSxQK35VsHuFpvyFJRWkcvxZi2CEmigLvc3FWBarDPXZrFAEP and/or an external block explorer. Contract memorized as first.
- 160. Deploy Result Gas limit:16374, Storage limit 526 bytes Proposing fee to the validator: ꜩ0.002139 The contract is owned by alice (tz1Mawer..) The initial balance (credit) is ꜩ0 Michelson code and the initial value "initial value" The originated contract address is KT1NmLBE.. Actual cost: Gas: 16275, Storage: 249 bytes Network fee for the new storage: ꜩ0.249 Network fee for the contract origination: ꜩ0.257
- 161. The wallet knowsthe new contract Not addresses but contracts this time. $ ./tezosclient list known contracts ↩ first: KT1NmLBEGeKrppHESUK9KEkHjj6i4677J3cS jun: tz1TGu6TN5GSez2ndXXeDX6LgUDvLzPLqgYV alice: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF
- 162. Check the stateof the contract $ ./tezosclient get script code for first ↩ { parameter string ; storage string ; code { .. } } $ ./tezosclient get script storage for first ↩ "initial value" $ ./tezosclient get balance for first ↩ 0 ꜩ
- 163. Call the SmartContract Same as the simple transaction we did, but specify the parameter with arg $ ./tezosclient transfer 0 from alice to first arg '"hello"' ↩ .. Transaction: Amount: ꜩ0 From: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF To: KT1NmLBEGeKrppHESUK9KEkHjj6i4677J3cS Parameter: "hello" This transaction was successfully applied Updated storage: "hello" Storage size: 241 bytes Consumed gas: 15762 ..
- 164. Did not workfor you? Check typo Your account alias is alice? Commands are designed intentionally long to avoid mistakes. Got “Fatal error” about the burn cap? Extending the storage size costs you: $ ./tezosclient transfer 0 from alice to first arg '"I am creative and give a very long string!"' ↩ Fatal error: The operation will burn ꜩ0.029 which is higher than the configured burn cap (ꜩ0). Use `burncap 0.029` to emit this operation.
- 165. Let’s check theresult $ ./tezosclient get script storage for first ↩ "whatever you sent" $ ./tezosclient get balance for first ↩ 100 ꜩ Non 0 if you transfer some tokens.
- 166. Congratulations! You are nowa Tezos engineer.
- 167. Smarter Contracts Returning Operations Byreturning non empty operation list, smart contracts can send tokens to other addresses, and call other smart contracts.
- 168. Smarter Contracts: Boomerang Ifsomeone sends non-zero token, return it to the source. Otherwise, do nothing. Function arguments: Storage: nothing Parameter: nothing In ML, we use type unit for the type of no specific data. () is the value of the type: ( () : unit )
- 169. Smarter Contracts: GlobalConstants Global constants to use: amount: The amount of transaction source: The address which initiated the transaction.
- 170. Smater Contracts: functionsfor ops. Functions to create operations: Operation.transaction : 'a > tez > 'a contract > operation Transfer token to the specified contract with a parameter, ex. Operation.transfer () 10tz contract Operation.get_contract : address > _ contract Obtain the contract of the given address. Type annotation is required to specify the contract type. ex. (Operation.get_contract adrs : unit contract)
- 171. Smater Contracts: Boomelang Conditional if e1 then e2 else e3 Nonempty list [ 1 ; 2 ; 3 ] Local definition let v = e1 in e2 Bind the result of e1 to variable v. let main (param : unit) (storage: unit) = let ops = if amount = 0tz then ([] : operation list) else [ Operation.transaction () amount (Operation.get_contract source : unit contract) ] in ( ops, () )
- 172.
- 173. Then Call! Check thetoken was returned to alice. $ ./tezosclient transfer 10 from alice to boomerang Balance updates: tz1MawerETND6bqJqx8GV3YHUrvMBCD.. ............ ꜩ0.004347 fees(tz1ddb9NMYHZi5UzPdzTZMYQQZoM95zgv,15) ... +ꜩ0.004347 Transaction: .. Balance updates: tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ... ꜩ10 KT1Lw7gDyYr2MFUVJLyA2sQuCSjsc1krcAkb ... +ꜩ10 Internal operations: Transaction: .. Balance updates: KT1Lw7gDyYr2MFUVJLyA2sQuCSjsc1krcAkb ... ꜩ10 tz1MawerETND6bqJqx8GV3YHUrvMBCDasRBF ... +ꜩ10
- 174. Advanced Excersize Simple banking:bank Parameter type unit Storage type Table of deposits, (address, tez) map: you can lookup the balance of each address. Behaviour If transaction amount is not 0tz, update the sender’s balance in the map. If amount is 0tz, send the balance of the sender recorded in the map. Then, reset the balance of sender of the map.
- 175. Hints を参考に。 Global constants amount, sender Thetransferred amount is 0 or not: amount = 0tz かamount <> 0tz Map operations: Map.find_opt, Map.update, Map.remove Branching by the result of Map.find_opt: Use pattern match: match result with None > .. | Some tez > .. ./contracts/cheat-sheet.md
- 176. Hints Deployment You can givethe initial empty map value by init '{}' Call You will need burncap when the call makes the size of map
- 177. Yet Another AdvancedExcersize The DAO attack used a contract attacker with the following behavior: The initial balance is 100tz If received 0tz, transact 10tz to bank If received non 0tz, If its balance exceeds 200tz, do nothing. Otherwise, transact 0tz to bank If transactions are implemented as function calls (in Ethereum), attacker can steal tokens from bank more than attacker’s deposit. Is the same possible in Tezos?