PoSME: Proof of Sequential Memory Execution via Latency-Bound Pointer Chasing with Causal Hash Binding

TL;DR

PoSME is a cryptographic primitive that enforces strict sequential computation using latency-bound pointer chasing and causal hash binding, offering resistance to time-memory trade-offs and practical benchmarks.

Contribution

It introduces PoSME, a novel primitive for sequential memory enforcement with formal bounds, high resistance, and practical implementation benchmarks across CPUs and GPUs.

Findings

Hash computation accounts for less than 3.5% of step cost.

GPU hardware is 14 to 19 times slower than consumer CPU.

PoSME provides a foundation for verifiable delay and Sybil resistance.

Abstract

We introduce PoSME (Proof of Sequential Memory Execution), a cryptographic primitive that enforces sustained sequential computation via latency-bound pointer chasing over a mutable arena. Each step reads data-dependent addresses, writes a block whose value and causal hash are mutually dependent (symbiotic binding), and chains the result into a global transcript. This yields three properties: (1) strict linear sequential memory-step enforcement, (2) high time-memory trade-off resistance (a tenfold penalty at a write density of 4, with a formal space-time lower bound that scales quadratically with the number of steps), and (3) a tight ASIC advantage bound by DRAM random-access latency rather than bandwidth. Benchmarks across 17 CPU platforms and 4 GPU architectures demonstrate that hash computation is under 3.5 percent of step cost and GPU hardware is 14 to 19 times slower than a consumer CPU. POSME requires no trusted setup and provides a foundation for verifiable delay, authorship attestation, and Sybil resistance.