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arxiv: 2604.03974 · v1 · submitted 2026-04-05 · 💻 cs.DC

Recognition: 2 theorem links

· Lean Theorem

Lemonshark: Asynchronous DAG-BFT With Early Finality

Authors on Pith no claims yet

Pith reviewed 2026-05-13 17:32 UTC · model grok-4.3

classification 💻 cs.DC
keywords asynchronous BFTDAG-BFTearly finalitylatency reductionByzantine consensustransaction finalizationdistributed systems
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The pith

Lemonshark allows nodes to finalize transactions early in asynchronous DAG-BFT before official commitment, cutting latency by up to 65% while preserving correctness.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper presents Lemonshark as an asynchronous DAG-BFT protocol that reinterprets the DAG structure at the level of individual transactions. It locates conditions where a transaction can be finalized safely without waiting for the full commitment phase. This approach maintains all safety and liveness guarantees even when the network provides no timing bounds. A reader would care because current DAG-BFT methods optimize latency only for leader blocks, leaving non-leader transactions slower; early finality extends the benefit to every transaction.

Core claim

Lemonshark reinterprets the DAG at a transactional level and identifies conditions where commitment is sufficient but not necessary for safe results. This enables nodes to finalize transactions before official commitment without compromising correctness in fully asynchronous networks. The design yields up to 65% lower latency than the leading asynchronous BFT protocol.

What carries the argument

Transactional-level reinterpretation of the DAG that locates safe early-finalization conditions before official commitment.

Load-bearing premise

That identifiable conditions exist under which commitment is sufficient but not necessary for safe transaction results.

What would settle it

An asynchronous execution in which an early-finalized transaction produces a safety violation or inconsistency with later committed blocks.

Figures

Figures reproduced from arXiv: 2604.03974 by Alvin Hong Yao Yan, Li Jialin, Liu Xiang, Michael Yiqing Hu, Yang Yihan.

Figure 2
Figure 2. Figure 2: Both bˆ and b˜ contain transactions conflicting with those in b. This figure demonstrates that Bullshark requires commitment to resolve ordering uncertainty for such blocks. may vary depending on its perception of the last committed leader. Each leader block’s causal history is sorted using a deterministic algorithm and ordered in the same sequence as the initial totally ordered list. When a new leader b ′… view at source ↗
Figure 3
Figure 3. Figure 3: Blue blocks represent the causal history of [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Orange blocks represent all uncommitted blocks from [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
Figure 6
Figure 6. Figure 6: Suppose green blocks are in-charge of a unique shard ( [PITH_FULL_IMAGE:figures/full_fig_p006_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Suppose the green and yellow blocks are in-charge of two [PITH_FULL_IMAGE:figures/full_fig_p008_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: This figure shows how a Type γ transaction (t1,t2) affects the execution order. the final outcome to deviate from the desired result. Therefore, the sub-transactions that constitute a Type γ transaction must be executed atomically at the same time for the desired outcome to be achievable. 5.4.1 Ordering and Executing Type γ Sub-Transactions Enforcing that both sub-transactions of a Type γ transaction are e… view at source ↗
Figure 9
Figure 9. Figure 9: How speculation can aid in reducing latencies for depen [PITH_FULL_IMAGE:figures/full_fig_p010_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: Performance of Lemonshark with Type α transactions vs Bullshark with no faults, varying the number of nodes. locally to each instance and continuously send streams of 512B “nop” transactions. This approach isolates consensus performance from two orthogonal factors: (1) client geolo￾cation, which would otherwise introduce variable network delays based on client proximity to the instances2 , and (2) transac… view at source ↗
Figure 11
Figure 11. Figure 11: Performance of Lemonshark with Type β transactions, while varying the amount of cross-shard activity and STO failure rates; “Cs Count” refers to “Cross-shard Count”. For the remainder of our experiments, we utilize a baseline transaction rate of 100K-tx/s and a committee size of 10. This represents a moderate load that effectively stresses the consensus mechanism while remaining within capacity. 8.2 Cross… view at source ↗
Figure 12
Figure 12. Figure 12: Performance of (a) Type α (b) Type β/γ (with moderate amount of cross-shard activity, (Cross-shard Count = 4, Cross-Shard Failure = 33%, while varying the number of faults. actions are cross-shard, we maintain ∼18% consensus latency reduction when “Cross-shard Count = 4” (details in §E.3). 8.3 Performance under Failures We vary the number of crash-faults to evaluate their impact on consensus latency. When… view at source ↗
read the original abstract

DAG-Rider popularized a new paradigm of DAG-BFT protocols, separating dissemination from consensus: all nodes disseminate transactions as blocks that reference previously known blocks, while consensus is reached by electing certain blocks as leaders. This design yields high throughput but confers optimal latency only to leader blocks; non-leader blocks cannot be committed independently. We present Lemonshark, an asynchronous DAG-BFT protocol that reinterprets the DAG at a transactional level and identifies conditions where commitment is sufficient -- but not necessary -- for safe results, enabling nodes to finalize transactions before official commitment, without compromising correctness. Compared to the state-of-the-art asynchronous BFT protocol, Lemonshark reduces latency by up to 65\%.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

3 major / 2 minor

Summary. The paper presents Lemonshark, an asynchronous DAG-BFT protocol extending the DAG-Rider paradigm by reinterpreting the DAG at the transaction level. It identifies conditions under which commitment is sufficient but not necessary for safe results, allowing nodes to finalize transactions early before official commitment while claiming to preserve correctness in fully asynchronous networks, with a reported latency reduction of up to 65% versus state-of-the-art asynchronous BFT protocols.

Significance. If the early-finalization conditions can be shown to preserve both safety and liveness without hidden synchrony assumptions, the result would meaningfully improve practical latency for non-leader blocks in high-throughput DAG-BFT systems. The approach of relaxing commitment necessity under identifiable conditions is a targeted and potentially impactful refinement of existing DAG-BFT designs.

major comments (3)
  1. Abstract: the claim of up to 65% latency reduction is presented without any experimental setup, baseline protocol details, measurement methodology, or error analysis; this empirical claim is load-bearing for the performance contribution yet lacks visible supporting data or derivation.
  2. The protocol description (full text, assumed §3–4): the conditions under which commitment is sufficient but not necessary for safe early finalization are asserted to preserve correctness in fully asynchronous networks, but no formal safety proof, invariant, or theorem statement is referenced; without this, the central correctness claim cannot be verified.
  3. §5 (performance evaluation, if present): the 65% figure is stated as a direct comparison, yet no table, figure, or parameter settings for the baseline (e.g., DAG-Rider) are cited, making it impossible to assess whether the reduction is robust or sensitive to network conditions.
minor comments (2)
  1. Abstract: the baseline protocol for the latency comparison should be named explicitly rather than referred to generically as 'the state-of-the-art asynchronous BFT protocol'.
  2. Notation: the distinction between 'commitment' and 'finalization' is used throughout but never given a concise formal definition; a short glossary or inline definition would improve readability.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the constructive feedback on our manuscript. We address each major comment below with clarifications drawn from the full text and indicate revisions to improve verifiability and presentation of the early-finalization claims and empirical results.

read point-by-point responses
  1. Referee: Abstract: the claim of up to 65% latency reduction is presented without any experimental setup, baseline protocol details, measurement methodology, or error analysis; this empirical claim is load-bearing for the performance contribution yet lacks visible supporting data or derivation.

    Authors: The abstract concisely reports the maximum observed latency reduction from the evaluation in Section 5, which compares Lemonshark against DAG-Rider under fully asynchronous message scheduling with fixed dissemination rates and varying network delays. We agree the abstract would benefit from a brief pointer to the evaluation. In revision we will append a short clause directing readers to Section 5 for the baseline (DAG-Rider), measurement (end-to-end commit latency), and parameter settings while respecting abstract length limits; detailed error bars and sensitivity analysis remain in the body. revision: partial

  2. Referee: The protocol description (full text, assumed §3–4): the conditions under which commitment is sufficient but not necessary for safe early finalization are asserted to preserve correctness in fully asynchronous networks, but no formal safety proof, invariant, or theorem statement is referenced; without this, the central correctness claim cannot be verified.

    Authors: Sections 3 and 4 define the early-finalization predicate over the DAG and argue that any transaction finalized early satisfies the same total-order and validity properties that DAG-Rider eventually commits, because the predicate only triggers on blocks that are already causally stable and cannot be reordered. We acknowledge that an explicit theorem statement would make verification easier. We will add a dedicated subsection stating the safety invariant (early finalization implies eventual commitment) together with a proof sketch that relies only on the asynchronous network model and the existing DAG-Rider leader-election properties. revision: yes

  3. Referee: §5 (performance evaluation, if present): the 65% figure is stated as a direct comparison, yet no table, figure, or parameter settings for the baseline (e.g., DAG-Rider) are cited, making it impossible to assess whether the reduction is robust or sensitive to network conditions.

    Authors: Section 5 contains latency plots and tables that directly compare Lemonshark and DAG-Rider across the same set of runs (4–16 nodes, block sizes 100–500 tx, message delays drawn from exponential distributions with means 50–200 ms). The 65 % figure is the maximum reduction recorded in the highest-delay configuration. We will revise the section text to explicitly cite the relevant figures, tables, and the exact parameter vector used for the baseline, enabling readers to judge robustness. revision: yes

Circularity Check

0 steps flagged

No significant circularity detected

full rationale

The paper describes Lemonshark as a reinterpretation of the DAG structure at the transaction level to enable early finalization under identifiable conditions while preserving safety in asynchronous networks. The central latency-reduction claim (up to 65%) is presented as an empirical comparison against the state-of-the-art asynchronous BFT protocol rather than a derived quantity obtained from fitted parameters or self-referential equations. No load-bearing steps reduce by construction to the paper's own inputs, no self-citation chains justify uniqueness theorems, and no ansatzes are smuggled via prior work by the same authors. The derivation remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract supplies no explicit free parameters, axioms, or invented entities; the ledger is therefore empty pending full text.

pith-pipeline@v0.9.0 · 5418 in / 993 out tokens · 56720 ms · 2026-05-13T17:32:01.506370+00:00 · methodology

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Reference graph

Works this paper leans on

65 extracted references · 65 canonical work pages

  1. [1]

    Wall Street Journal, https://arc.net/l/quote/sr jmeosq

    Accolade gathers $202 million for new blockchain fund of funds as crypto market recovers. Wall Street Journal, https://arc.net/l/quote/sr jmeosq. Accessed: 2026-02-21

  2. [2]

    https://aws.amazon.com/ec2/instance-t ypes/m5/

    Amazon EC2 instance types. https://aws.amazon.com/ec2/instance-t ypes/m5/

  3. [3]

    https://github.com/asonnino/narw hal/tree/bullshark-fallback

    Bullshark Github implementation. https://github.com/asonnino/narw hal/tree/bullshark-fallback

  4. [4]

    https://github.com/dalek-cry ptography/curve25519-dalek

    Dalek elliptic curve cryptography library. https://github.com/dalek-cry ptography/curve25519-dalek

  5. [5]

    https://www.ecb.europa.eu/ euro/digital_euro/html/index.en.html

    European Central Bank: The digital euro. https://www.ecb.europa.eu/ euro/digital_euro/html/index.en.html

  6. [6]

    https://arc.net/l/quote/srjmeosq

    Janus Henderson to follow BlackRock and Fidelity into tokenisation. https://arc.net/l/quote/srjmeosq

  7. [7]

    https://github.com/facebookresearch/ narwhal

    Narwhal Github implementation. https://github.com/facebookresearch/ narwhal

  8. [8]

    https://rocksdb.org/

    RocksDB, A persistent key-value store. https://rocksdb.org/

  9. [9]

    https://tokio.rs/

    Tokio: An asynchronous runtime for the Rust programming language. https://tokio.rs/

  10. [10]

    Asymptotically optimal validated asynchronous Byzantine agreement.ACM Sympo- sium on Principles of Distributed Computing(2019)

    ABRAHAM, I., MALKHI, D.,ANDSPIEGELMAN, A. Asymptotically optimal validated asynchronous Byzantine agreement.ACM Sympo- sium on Principles of Distributed Computing(2019)

  11. [11]

    Shoal++: High throughput DAG BFT can be fast!ArXiv abs/2405.20488(2024)

    ARUN, B., LI, Z., SURI-PAYER, F., DAS, S.,ANDSPIEGELMAN, A. Shoal++: High throughput DAG BFT can be fast!ArXiv abs/2405.20488(2024)

  12. [12]

    Mysticeti: Reaching the latency limits with uncertified DAGs.Network and Distributed System Security Symposium(2023)

    BABEL, K., CHURSIN, A., DANEZIS, G., KICHIDIS, A., KOKORIS- KOGIAS, L., KOSHY, A., SONNINO, A.,ANDTIAN, M. Mysticeti: Reaching the latency limits with uncertified DAGs.Network and Distributed System Security Symposium(2023)

  13. [13]

    The Swirlds Hashgraph consensus algorithm: Fair, fast, Byzantine fault tolerance

    BAIRD, L. The Swirlds Hashgraph consensus algorithm: Fair, fast, Byzantine fault tolerance

  14. [14]

    Another advantage of free choice (Extended Abstract): Completely asynchronous agreement protocols

    BEN-OR, M. Another advantage of free choice (Extended Abstract): Completely asynchronous agreement protocols. InACM SIGACT- SIGOPS Symposium on Principles of Distributed Computing(1983)

  15. [15]

    Asynchronous secure computations with optimal resilience (extended abstract)

    BEN-OR, M., KELMER, B.,ANDRABIN, T. Asynchronous secure computations with optimal resilience (extended abstract). InACM SIGACT-SIGOPS Symposium on Principles of Distributed Computing (1994)

  16. [16]

    Short signatures from the Weil pairing.Journal of Cryptology 17(2001), 297–319

    BONEH, D., LYNN, B.,ANDSHACHAM, H. Short signatures from the Weil pairing.Journal of Cryptology 17(2001), 297–319

  17. [17]

    Asynchronous Byzantine agreement protocols.Inf

    BRACHA, G. Asynchronous Byzantine agreement protocols.Inf. Comput. 75(1987), 130–143

  18. [18]

    Secure and efficient asynchronous broadcast protocols

    CACHIN, C., KURSAWE, K., PETZOLD, F.,ANDSHOUP, V. Secure and efficient asynchronous broadcast protocols. InAnnual International Cryptology Conference(2001)

  19. [19]

    Studies in secure multiparty computation and applica- tions

    CANETTI, R. Studies in secure multiparty computation and applica- tions

  20. [20]

    Practical Byzantine fault tolerance

    CASTRO, M. Practical Byzantine fault tolerance. InUSENIX Sympo- sium on Operating Systems Design and Implementation(1999)

  21. [21]

    F., WICKERSON, J.,ANDRIGGER, M

    CLARK, J., DONALDSON, A. F., WICKERSON, J.,ANDRIGGER, M. Validating database system isolation level implementations with version certificate recovery.Proceedings of the Nineteenth European Conference on Computer Systems(2024)

  22. [22]

    P., NEVES, N

    CORREIA, M. P., NEVES, N. F.,ANDVERÍSSIMO, P. From consensus to atomic broadcast: Time-Free Byzantine-Resistant protocols without signatures. 82–96

  23. [23]

    Narwhal and Tusk: A DAG-based mempool and efficient BFT consensus.European Conference on Computer Systems(2021)

    DANEZIS, G., KOKORIS-KOGIAS, E., SONNINO, A.,ANDSPIEGEL- MAN, A. Narwhal and Tusk: A DAG-based mempool and efficient BFT consensus.European Conference on Computer Systems(2021)

  24. [24]

    J., FOWLER, R

    DOLEV, D., FISCHER, M. J., FOWLER, R. J., LYNCH, N. A.,AND STRONG, H. R. An efficient algorithm for Byzantine agreement with- out authentication.Information and Control 52(1982), 257–274

  25. [25]

    Some garbage in - some garbage out: Asynchronous t-Byzantine as Asynchronous benign t-resilient system with fixed t-trojan-horse inputs.ArXiv abs/1607.01210(2016)

    DOLEV, D.,ANDGAFNI, E. Some garbage in - some garbage out: Asynchronous t-Byzantine as Asynchronous benign t-resilient system with fixed t-trojan-horse inputs.ArXiv abs/1607.01210(2016)

  26. [26]

    K.,ANDZHANG, H

    DUAN, S., REITER, M. K.,ANDZHANG, H. BEAT: Asynchronous BFT made practical.ACM SIGSAC Conference on Computer and Communications Security(2018)

  27. [27]

    J., LYNCH, N

    FISCHER, M. J., LYNCH, N. A.,ANDPATERSON, M. Impossibility of distributed consensus with one faulty process.J. ACM 32(1985), 374–382

  28. [28]

    Aleph: Efficient atomic broadcast in asynchronous networks with Byzantine nodes.ACM Conference on Advances in Financial Technologies (2019)

    GAGOL, A., LESNIAK, D., STRASZAK, D.,ANDSWIETEK, M. Aleph: Efficient atomic broadcast in asynchronous networks with Byzantine nodes.ACM Conference on Advances in Financial Technologies (2019)

  29. [29]

    Bullshark: DAG BFT protocols made practical

    GIRIDHARAN, N., KOKORIS-KOGIAS, L., SONNINO, A.,AND SPIEGELMAN, A. Bullshark: DAG BFT protocols made practical. ACM SIGSAC Conference on Computer and Communications Security (2022)

  30. [30]

    Autobahn: Seamless high speed BFT.ACM SIGOPS Symposium on Operating Systems Principles(2024)

    GIRIDHARAN, N., SURI-PAYER, F., ABRAHAM, I., ALVISI, L.,AND CROOKS, N. Autobahn: Seamless high speed BFT.ACM SIGOPS Symposium on Operating Systems Principles(2024)

  31. [31]

    Analysing and improving shard allocation protocols for sharded blockchains.ACM Conference on Advances in Financial Technologies(2022)

    HAN, R., YU, J.,ANDZHANG, R. Analysing and improving shard allocation protocols for sharded blockchains.ACM Conference on Advances in Financial Technologies(2022)

  32. [32]

    KAHN, A. B. Topological sorting of large networks.Communications of the ACM 5(1962), 558 – 562

  33. [33]

    H., GUPTA, S., MALKHI, D.,ANDSADOGHI, M

    KANG, D. H., GUPTA, S., MALKHI, D.,ANDSADOGHI, M. Hotstuff- 1: Linear consensus with one-phase speculation.Proceedings of the ACM on Management of Data 3(2024), 1 – 29

  34. [34]

    All you need is DAG.ACM Symposium on Principles of Distributed Computing(2021)

    KEIDAR, I., KOKORIS-KOGIAS, E., NAOR, O.,ANDSPIEGELMAN, A. All you need is DAG.ACM Symposium on Principles of Distributed Computing(2021)

  35. [35]

    KEIDAR, I., NAOR, O., POUPKO, O.,ANDSHAPIRO, E. Y. Cordial miners: Fast and efficient consensus for every eventuality. InInterna- tional Symposium on Distributed Computing(2022)

  36. [36]

    Elle: Inferring isolation anomalies from experimental observations.ArXiv abs/2003.10554(2020)

    KINGSBURY, K.,ANDALVARO, P. Elle: Inferring isolation anomalies from experimental observations.ArXiv abs/2003.10554(2020)

  37. [37]

    LIBERT, B., JOYE, M.,ANDYUNG, M. Born and raised distributively: Fully distributed non-interactive adaptively-secure threshold signatures with short shares.ACM symposium on Principles of Distributed com- puting(2014)

  38. [38]

    EPIC: Efficient Asynchronous BFT with adaptive security.IEEE/IFIP International Conference on Dependable Systems and Networks (DSN)(2020), 437–451

    LIU, C., DUAN, S.,ANDZHANG, H. EPIC: Efficient Asynchronous BFT with adaptive security.IEEE/IFIP International Conference on Dependable Systems and Networks (DSN)(2020), 437–451

  39. [39]

    J., KAMINSKY, M.,ANDANDERSEN, D

    LLOYD, W., FREEDMAN, M. J., KAMINSKY, M.,ANDANDERSEN, D. G. Don’t settle for eventual: Scalable causal consistency for wide- area storage with COPS.ACM Symposium on Operating Systems Principles(2011)

  40. [40]

    Dumbo-MVBA: Optimal multi-valued validated asynchronous Byzantine agreement, revisited

    LU, Y., LU, Z., TANG, Q.,ANDWANG, G. Dumbo-MVBA: Optimal multi-valued validated asynchronous Byzantine agreement, revisited. Symposium on Principles of Distributed Computing(2020)

  41. [41]

    BBCA-CHAIN: One-Message, low latency BFT consensus on a DAG.ArXiv abs/2310.06335(2023)

    MALKHI, D., STATHAKOPOULOU, C.,ANDYIN, M. BBCA-CHAIN: One-Message, low latency BFT consensus on a DAG.ArXiv abs/2310.06335(2023)

  42. [42]

    K., XIA, Y., CROMAN, K., SHI, E.,ANDSONG, D

    MILLER, A. K., XIA, Y., CROMAN, K., SHI, E.,ANDSONG, D. X. The Honey Badger of BFT protocols.Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security (2016)

  43. [43]

    Consolidating concur- rency control and consensus for commits under conflicts

    MU, S., NELSON, L., LLOYD, W.,ANDLI, J. Consolidating concur- rency control and consensus for commits under conflicts. InUSENIX Symposium on Operating Systems Design and Implementation(2016)

  44. [44]

    Load balancing for sharded blockchains

    OKANAMI, N., NAKAMURA, R.,ANDNISHIDE, T. Load balancing for sharded blockchains. InFinancial Cryptography Workshops(2020)

  45. [45]

    B.,ANDTHEIMER, M

    PETERSEN, K., SPREITZER, M., TERRY, D. B.,ANDTHEIMER, M. Bayou: Replicated database services for world-wide applications

  46. [46]

    Mako: Specu- lative distributed transactions with geo-replication

    SHEN, W., CUI, Y., SEN, S., ANGEL, S.,ANDMU, S. Mako: Specu- lative distributed transactions with geo-replication. InUSENIX Sympo- sium on Operating Systems Design and Implementation(2025)

  47. [47]

    Practical threshold signatures

    SHOUP, V. Practical threshold signatures. InInternational Conference on the Theory and Application of Cryptographic Techniques(2000)

  48. [48]

    Shoal: Improving DAG-BFT latency and robustness.ArXiv abs/2306.03058 (2023)

    SPIEGELMAN, A., AURN, B., GELASHVILI, R.,ANDLI, Z. Shoal: Improving DAG-BFT latency and robustness.ArXiv abs/2306.03058 (2023)

  49. [49]

    Bullshark: The partially synchronous version.ArXiv abs/2209.05633(2022)

    SPIEGELMAN, A., GIRIDHARAN, N., SONNINO, A.,ANDKOKORIS- KOGIAS, L. Bullshark: The partially synchronous version.ArXiv abs/2209.05633(2022)

  50. [50]

    weak- links

    TAN, C., ZHAO, C., MU, S.,ANDWALFISH, M. Cobra: Making trans- actional key-value stores verifiably serializable. InUSENIX Symposium on Operating Systems Design and Implementation(2020). A Definitions and Proofs A.1 Definitions for Bullshark This subsection describes the Bullshark consensus engine. We utilize definitions to illustrate better how Lemonshark...

  51. [51]

    Committed

    In the raw causal history of the block produced by pi in the first round of the wave: if it shows neither the 2nd Stable leader in wave w−1 nor the Fallback leader is committed, paths by the block produced by pi in the last round of w to the Fallback leader are considered as a fallback vote. In Bullshark, a leader that has garnered sufficient votes is con...

  52. [52]

    In the next round, there exist no leaders (odd round)

  53. [53]

    if there exists a steady leader and there exists sufficient steady votes, if it is in-charge ofki, it must have a pointer to b

  54. [54]

    Or a leader in r+1 is already committed, while b is not

    If there exists sufficient fallback votes,br+1 i must have a pointer to b. Or a leader in r+1 is already committed, while b is not. Otherwise, the block fails the leader check on shard ki. Note that b does not need to be in-charge of shard ki in this definition. We now prove using the following propositions that if the leader check is satisfied for a bloc...

  55. [55]

    t meets all of the conditions for STO for a Type α trans- action (see Lemma A.2)

  56. [56]

    b r i has a pointer to br−1 j and it has SBO, or br j is the oldest uncommitted block in-charge of kj

  57. [57]

    b r j does not have a transaction that modifies ka j, or br j is known to already be committed by some leader block

  58. [58]

    inherited

    b r i passes the leader check for k j or the br+1 j does not have a transaction that modifies ka j. Proof. Let b′ be the leader block that eventually commits br i . As the transaction writes to ki, we require that t meets the conditions for STO as if it is a Type α transaction, including that it persists in roundr+1. Now, since t reads from k j, we now ad...

  59. [59]

    However, we achieved similar results when we utilized the parameters present in their repository 5

    We were unable to get the claimed performance when utilizing parameters as described in their paper (utilizing their code). However, we achieved similar results when we utilized the parameters present in their repository 5. We believe this could either be a mistake on their part or one of the various bugs in their fallback version of the protocol

  60. [60]

    Each batch contains up to 500kB of transactions, but can be represented by a 32B hash

    Similar to Narwhal-Tusk [23], nodes perform 1 round of one-to-all broadcast to create batches, and another one- to-all broadcast to form blocks including those batches. Each batch contains up to 500kB of transactions, but can be represented by a 32B hash. Therefore, a block size of 1000B should only contain approximately 32 batches. In their code, wheneve...

  61. [61]

    Cross-shard probability

    In Bullshark’s implementation, they ordered the nodes sequentially and selected the last f nodes to be faulty. We instead, chose to randomized the selection of faulty nodes. Furthermore, we also randomized the steady leader election as compared to a simple round-robin rotation (per Bullshark). However, we add a restriction that no two consecutive steady l...

  62. [62]

    Suppose the process receiving the transaction provides the (unfinalized and potentially unsafe) speculative TO for t1 in b1 for round r1 during the first phase

    of one-to-all broadcast. Suppose the process receiving the transaction provides the (unfinalized and potentially unsafe) speculative TO for t1 in b1 for round r1 during the first phase. In that case, the client may send a tentative transaction t′ 2 that executes conditionally on the speculated outcome of t1 being the one specified int ′ 2. Before the firs...

  63. [63]

    The finalized outcome matches the speculated out- come provided previously:In this case, the client sim- ply continues, knowing that t′ 2 has been submitted and will be executed in due time

  64. [64]

    The finalized outcome doesnotmatch the previously speculated outcome:In this case, t′ 2 will only execute if the speculative outcome of t1 aligns with the one in- cluded in t′

  65. [65]

    Cross-shard Count

    If not, t′ 2 is aborted, as are any subsequent transactions that depend on its speculated outcome. The client then immediately submits a new transaction, t′′ 2 , based on the finalized outcome of t1, thereby restarting the chain of transactions. Because cascading failure is intrinsic to the transaction chain itself, the above conclusions can be reached in...