Mobile blockchain transactions require low latency
for practical deployment. This paper presents a
smartphone-native Trustchain system developed as
part of a collaborative research project where five
students implement Trustchain from scratch, each
optimizing a different performance metric: latency,
robustness, storage, throughput, and battery effi-
ciency. This work focuses on latency optimiza-
tion through a novel modular architecture imple-
mented in Rust/Kotlin that enables runtime proto-
col switching—the first such capability in mobile
blockchain implementations.
The evaluation compares two transport layers: a
lightweight UDP implementation and a business-
grade P2P solution (Iroh). Testing on Android de-
vices demonstrates end-to-end round-trip laten-
cies from 11.8 ms under optimal conditions to
240 ms at extreme loads (500 MPS), with UDP
achieving consistent 11.8ms median latency and
Iroh showing 18.2ms for typical payloads. Results
show clear trade-offs between protocol complexity
and performance, providing guidance for selecting
transport mechanisms in different mobile deploy-
ment scenarios. All code is released open-source to
the Tribler project for reproducibility.

TrustChain is a scalable, lightweight blockchain architecture that avoids global consensus by maintaining a personal chain of co-signed interactions for each peer, forming a directed acyclic graph. While its structure makes it promising for mobile and resource constrained environments, its behavior under real world conditions, such as the time it takes to restore connectivity, remains underexplored. This paper presents an implementation of TrustChain in Rust for Android mobile devices and evaluates its robustness under network disconnections across two protocols: UDP and Iroh over QUIC. Robustness is defined as the time elapsed between network connectivity restoration and the successful exchange of the first valid TrustChain message between peers. Experiments involved controlled Wi-Fi interruptions, measuring the reconnection time for each protocol. The findings reveal trade-offs between protocol simplicity and recovery performance. UDP demonstrated consistent low-latency reconnection times between 4 and 6 seconds, averaging 5 seconds, due to its stateless nature and lack of connection recovery overhead. In contrast, Iroh reconnection times ranged from 4.5 to 11.5 seconds, with most values between 6 and 8 seconds, due to QUIC's timeout strategy, DNS-based peer discovery, and relay reconnection overhead. The results provide insights for deploying decentralized systems in mobile contexts and highlight open challenges in peer reconnection for lightweight blockchain protocols. This study also proposes improvements and directions for future work, including multi-peer evaluation, measuring different Wi-Fi congestion levels, or experimentation with other network protocol stacks.

Blockchain technologies offer decentralized, secure, and transparent transaction sys tems but face significant scalability challenges, especially in mobile and peer-to-peer environments. Directed Acyclic Graph (DAG)-based protocols, such as Trustchain, present a promising alternative by allowing each agent to maintain a personal chain of relevant transactions, thereby improving throughput and reducing resource consump tion. Despite its theoretical potential, Trustchain has not yet been effectively imple mented for smartphones. To evaluate performance, we provide an implementation over two communication protocols, focusing on throughput. We found that our QUIC-based implementation displays an over three times throughput improvement when keeping a QUIC connection open, and can confidently store at least 28 536-byte blocks per sec ond. However, our UDP-based version outperforms our implementation, confidently storing at least 500 668-byte blocks per second.

Smartphones offer limited storage and memory, con- straints that conventional blockchains struggle to meet, yet they are also the devices where user- owned transaction chains promise the most value. We present the first empirical study of TrustChain, a DAG-based per-peer ledger running entirely on mobile hardware. A Rust implementation and open- source benchmark evaluate how flush-interval batch- ing (k) and lossless compression affect a single node scaling from 103 to 106 blocks.
On a Galaxy S8 and Pixel-6 emulator, RAM stays below 600 MB and compressed disk use below 0.5 GB at one million blocks (128 B payload). Insert la- tency remains interactive (< 8 ms) with disk:100 flushing; moderate batching (k ≈ 500) cuts CPU load by roughly 45 % without harming durabil- ity. Lightweight compression (LZ4-1, Zstd-1) trims space by 20 to 30 % at a sub-10 ms cost, with diminishing returns at higher levels. End-to-end tests show storage is never the bottleneck, raw UDP achieving a 7 ms median RTT.
Taken together, the implementation and measure- ment dataset provide a concrete reference for deploy- ing DAG-based chains on smartphones and highlight opportunities for advancing mobile blockchain tech- nology.

Blockchain is already a widely adopted solution which can achieve decentralized storage in trustless settings. However, it is infamous for its high energy demands, making it difficult to operate on mobile phones with limited battery life. Among many design decisions in a blockchain implementation, is the choice of the communication protocol used for messaging between the participants. This work systematically evaluates the energy efficiency of custom blockchain implementations: over UDP and over QUIC with Iroh Rust crate for Android devices. The results demonstrate a higher energy demand by the QUIC-based implementation, with up to 34\% faster battery discharge on average compared to the UDP approach. Investigations show different energy usage per CPU and Wi-Fi components, and network traffic profile during the application's operation. These findings highlight the trade-offs related to energy efficiency in designing a blockchain-based system.