Scalar DL is a tamper-evident and scalable database system.

1. Scalar DL Technical Overview
1 Jan, 2021
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Scalar DL: Tamper-Evident and Scalable Database System
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3. © 2021Scalar, inc.
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Key Characteristics in Scalar DL
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Tamper-evident Scalable Correct
Database-agnostic Cloud-agnostic
Byzantine faults can be detected
as long as N > f
Performance and availability
can be linearly scaled
No intermediate states are visible,
and data is always up-to-date
No dependency on
particular database products
No dependency on
particular public clouds
N: # of administrative domains in a
database system, f: # of faulty domains
Cassandra, Amazon DynamoDB, Azure
Cosmos DB, and JDBC-supported major
RDBMSs are supported.
AWS, Azure, EKS, and AKS are
supported.
ACID-compliant and strong consistent
database system.
DVi = DV / N・RF
(RF: Replication Factor << N)

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Scalar DL System Architecture
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Pattern 1
Ledger
Pattern 2
Pattern 3
Client SDK
Ledger
Ordering
Client SDK
Proofs
Ledger
Client SDK
Smart
Contract
(signed)
Private keys Public keys
Auditor

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Scalar DL: Ledger
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User (Client)
Java
Contract
Signature
Private Key
Scalar DL network
function invoke() {
if (accounts[0].data.balance < args.val) {
throw new Error(“not enough balance”);
}
accounts[0].data.balance -= args.val;
accounts[1].data.balance += args.val;
results = { … };
}
Payment Contract
Request :
(contract, args, sig)
Asset ID Age Data (before) Data (after) Sigs Func (ref) Args Hash
A 1 { } { balance = 100,
…}
charge { val = 100 }
B 1 { }
{ balance = 200,
…} charge { val = 200 }
A 2 { A: {balance = 100},
B: {balance = 200} …}
{ balance = 90,
…}
payment { val = 10 }
SN = Func (SN-1 , Args)
Deterministic & TE TE
If S0 is TE ⇒ SN is TE
Public Key
B 2 { A: {balance = 100},
B: {balance = 200} …}
{ balance = 210,
…} payment { val = 10 }
H(A1)
H(B1)
State
hash
chain
Tamper Evidence (TE) of ledger entries:
Arguments
{ accounts = [“A”, “B”], val = 10, …}
* includes other accounts data
Argument

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Scalar DL: Auditor
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Auditor
managed by
a different organization
Client
Execute
Asset Proof
Request Proof
Asset Proof
T
Ledger
Compare to
detect
tampering
Auditor manages the proofs of execution to recompute assets without trusting
the integrity of data given from Ledger (1 patented, 1 patent-pending)

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Scalar DL: Ordering
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Client SDK
Scalar DL
Ordering
Private key
Smart
Contract
(signed)
Extracts parallelism
by utilizing partial order property
of contracts execution
without violating determinism
(patented) Execute contracts independently
…
Compare to
detect
tampering

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Key Differences between Public Blockchains and Scalar DL
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Public Blockchains
(Ethereum …)
Scalar DL
• History diverges in normal cases
– It diverges even if no malicious
activities ⇒ Impossible to
guarantee finality
• History diverges only in abnormal cases
– If it diverges, it is caused by
malicious activities ⇒ Possible to
guarantee finality
IEEE ICDCS Workshop’16

9. © 2021Scalar, inc.
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Key Differences between Private Blockchains and Scalar DL
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Private/Consortium Blockchains
(HL fabric, Tendermint…)
Scalar DL
• Execution and validation are coupled
⇒ Hard to Scale
• Execution and validation are decoupled
⇒ Scalable and Flexible
• Data is totally ordered
⇒ Hard to parallelize
• Data is partially ordered
⇒ Easy to parallelize
Sequential processing is required
Parallelizable
Should be
homogeneous
performance

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Unique Features 1 : ACID Nested Contract Execution
• Multiple contracts can be executed atomically
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Contract 1
Transaction
Tamper-evident ledger
Contract 2
Contract 3
Atomic
execution

11. © 2021Scalar, inc.
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Unique Features 2 : User-defined Function (patent-pending)
• Function is a business logic for creating deletable and easy to search
records
• Remedy the downsides of ledger structure and tamper-evidence property
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Mutable database
Function
Contract
Transaction
Tamper-evident ledger
Atomic
execution
Business logic
Evidence that business
logic is executed

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Benefits of User-defined Function
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App
Not deletable
Not searchable flexibly
App
Not tamper-evident
Blockchain
DB
App DB Blockchain
Inconsistent
App
Scalar DL
log
log
Mutable records
Tamper-evident records
Tamper-evident
Deletable
Searchable flexibly
Consistent

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Benchmark Results
• Each node: i3.4xlarge (16 vCPUs, 122 GB DRAM, 1900 GB NVMe SSD * 2
• Workload: Writing evidence of operations
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Achieved 90 % scalability in
100-node cluster
(Compared to the Ideal TPS based on
the performance of 3-node cluster)

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Preliminary Benchmark Results with Caliper
• Caliper for Scalar DL is supported (unofficially)
– https://github.com/scalar-labs/caliper (scalardl branch)
• Smallbank
– Fabric 1.4.1 (3 peers + 3 orderers), Scalar DL (3 C* + 3 Scalar DL nodes)
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0
2
4
6
8
10
12
14
16
18
20
0 50 100 150 200 250 300 350
Average
Latency
(s)
Throughput (tps)
Fabric (3org1peer)
Fabric (1org3peer)
Scalar DLT
Fabric 1.4.1, EP=ALL
Fabric 1.4.1, EP=1/3

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Verification Results
• Scalar DL has been heavily tested with Jepsen and our
destructive tools
– Note that Jepsen tests are created and conducted by Scalar
– It has passed both tests for a long time
– See https://github.com/scalar-labs/scalar-jepsen for more detail
• TLA+ formal verification is also passing
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Jepsen
Passed

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Confidential
Use Cases : Where to use Scalar DL
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• Data integrity is required
– Data can not be altered or deleted maliciously
• Scalability is required
– Many requests from many end-users or devices
• There is a main organization
– And there are a few auditors
• On-demand tamper detection is acceptable
Digital evidence
One of our focuses: