Nomos currently uses bincode for all serialization. While fast and simple, bincode lacks support for schema evolution and cross-language compatibility—two features increasingly important as the ecosystem scales.

2. Selection Criteria

We evaluated candidate encoding formats based on:

Schema Evolution – Supports changes to data structures without breaking compatibility.
Security – Handles untrusted inputs safely.
Performance – Fast to serialize and deserialize.
Determinism – Always produces identical output for the same input.
Cross-language Compatibility – Available and maintained across multiple languages.

3. Format Comparison (P2P-Relevant Formats)

Encoding Format	Evolution	Deterministic	Security	Lang Support	Usage
Protobuf	✓	△	⬤⬤◯	⬤⬤⬤	Cosmos SDK, libp2p
Borsh	—	✓	⬤⬤⬤	⬤⬤◯	NEAR, Solana programs
SCALE	—	✓	⬤⬤◯	⬤◯◯	Polkadot
Bincode	—	✓	⬤⬤◯	⬤◯◯	Solana validators
CBOR	✓	△	⬤⬤◯	⬤⬤⬤	Cardano, IPFS
MsgPack	△	△	⬤◯◯	⬤⬤⬤	Algorand
SSZ	—	✓	⬤⬤⬤	⬤◯◯	Ethereum 2.0

4. Tooling Considerations

Serde-Generate

https://crates.io/crates/serde-generate

Auto-generates serializers for Rust types, but fails with complex constructs like Risc0LeaderProof due to issues with the tracing feature. Adding schemas manually is also non-trivial.

Canonical Protobuf in Rust

https://crates.io/crates/prost

We can use prost with deterministic configurations:

// In build.rs - use BTreeMap for consistent key ordering
let mut config = prost_build::Config::new();
config.btree_map(&["."]); // Apply to all map fields
config.compile_protos(&["your.proto"], &["."])?;

Manual canonicalization wrapper:

use prost::Message;

fn encode_with_prost<T: Message>(msg: &T) -> Vec<u8> {
    // Standard prost encoding. Output is deterministic if:
    // - map fields use BTreeMap via build config
    // - .proto field tag numbers match declaration order
    // - unknown or unset optional fields are avoided
    let mut buf = Vec::new();
    msg.encode(&mut buf).unwrap();
    buf
}

5. Why Evolution Matters

// V1
struct Block { height: u64, hash: [u8; 32] }

// V2
struct Block { height: u64, hash: [u8; 32], timestamp: u64 }

Rigid encodings like bincode break when structures evolve. Nomos may support thousands of clients, making coordinated upgrades costly. Formats that support optional fields and schema evolution reduce this friction.

6. Planning for Multi-Language Support

Support for multiple implementations matters most post-adoption. Initially, most ecosystems rely on one client. However, protocol-level encoding should avoid locking into a single ecosystem from the start.

7. Serialization Benchmark Analysis

Benchmark Overview

This analysis compares 8 serialization formats: Bincode, Borsh, CBOR, JSON, MessagePack, Protobuf, SCALE, and SSZ. The benchmarks test performance on different data types and scales.

Top Observations

Bincode offers best performance for small and medium-sized data
SCALE and Borsh perform best on large structures
Protobuf offers compact encoding size and moderate throughput

Simple Structs Serialization (Roundtrip Performance)

Encoding Format	Roundtrip Time	Size (bytes)	Throughput (Melem/s)
Bincode	607.66 ns	12	82.28
Borsh	775.14 ns	12	64.51
SSZ	947.31 ns	12	52.78
SCALE	1.06 µs	10	47.31
Protobuf	1.21 µs	9	41.24
MessagePack	2.12 µs	13	23.63
JSON	3.74 µs	31	13.36
CBOR	5.70 µs	22	8.77

Binary Structs Performance

Encoding Format	Roundtrip Time	Size (bytes)	Throughput (Melem/s)
Bincode	1.59 µs	13	31.55
Borsh	1.81 µs	9	27.64
SCALE	1.83 µs	6	27.25
Protobuf	2.66 µs	7	18.81
MessagePack	3.19 µs	7	15.66
SSZ	4.27 µs	9	11.70
CBOR	4.82 µs	12	10.37
JSON	4.99 µs	20	10.03

Large Structs Performance

Encoding Format	Roundtrip Time	Size (bytes)	Throughput (Kelem/s)
SCALE	2.85 µs	647	1,755
Borsh	3.05 µs	700	1,637
Protobuf	4.81 µs	643	1,041
Bincode	5.29 µs	772	946
SSZ	8.57 µs	589	583
CBOR	18.13 µs	720	276
MessagePack	18.45 µs	618	271
JSON	27.11 µs	1,318	184

Performance Scaling Characteristics

Format	Simple Structs	Binary Structs	Large Structs	Overall Scalability
Bincode	⬤⬤⬤	⬤⬤⬤	⬤⬤◯	Strong
SCALE	⬤⬤◯	⬤⬤⬤	⬤⬤⬤	Strong
Borsh	⬤⬤◯	⬤⬤◯	⬤⬤⬤	Strong
Protobuf	⬤⬤◯	⬤⬤◯	⬤⬤◯	Good
SSZ	⬤◯◯	⬤◯◯	⬤◯◯	Good
MessagePack	⬤◯◯	⬤◯◯	⬤◯◯	Good
CBOR	⬤◯◯	⬤⬤◯	⬤◯◯	Moderate
JSON	⬤◯◯	⬤◯◯	⬤◯◯	Moderate

8. Encoding Evaluation and Conclusion

Benchmark results show meaningful performance differences across formats, especially in large and nested structures. While bincode leads in raw speed for small data, SCALE and Borsh outperform others in large-structure throughput.

Good alternatives to consider:

Protobuf – Supports schema evolution, great language support, and offers compact size with moderate performance.
Borsh and SCALE – Compact and deterministic; good performance, but lack schema evolution and broader tooling.

Each has trade-offs. The decision depends on the need for schema evolution, performance, cross-language support, and implementation simplicity.

9. How to run benchmarks

To run the benchmarks, clone the repository and execute:

cargo bench

README.md Unescape Escape

Choosing the Right Encoding for Networking

1. Introduction