What Are the Bandwidth Requirements for Post-Quantum Transactions?

Post-quantum transactions require more bandwidth than ECDSA-based transactions due to larger signature and key sizes. SPHINCS+ signatures range from 7-49 KB compared to ECDSA's 64-72 bytes. Network infrastructure must accommodate this increase while maintaining acceptable transaction throughput.

Signature size comparison: ECDSA produces ~72 byte signatures. Dilithium ranges 2.4-4.6 KB. SPHINCS+ ranges 7-49 KB depending on security and performance parameters. A 100x-500x increase affects block sizes, mempool management, and network propagation.

Key size impact: ECDSA public keys are 33-65 bytes. Kyber-768 public keys are ~1,184 bytes. SPHINCS+ public keys are 32-64 bytes. Key storage and transmission requirements increase, though address formats can compress public key commitments.

Block size considerations require either larger blocks or fewer transactions per block. Layer-1 designs must balance throughput against propagation delays that larger blocks create. Node synchronization and initial blockchain download times increase proportionally.

Optimization techniques mitigate bandwidth impact: signature aggregation (where applicable), key reuse protocols, hierarchical signature schemes, and compression algorithms. Protocol-level design choices can reduce effective bandwidth overhead.

Modern infrastructure handles the increase. Contemporary internet speeds and storage costs make post-quantum transaction sizes manageable. A 50 KB transaction is trivial compared to streaming video or software downloads. Mobile networks easily accommodate larger transactions.

SynX network architecture accounts for Kyber-768 and SPHINCS+ bandwidth requirements with optimized block structures and propagation protocols. The larger cryptographic elements are balanced against security benefits quantum resistance provides.