Sei Research Initiative

SIP-5: a post-quantum upgrade path for Sei

Jul 27, 2026

SIP-5: a post-quantum upgrade path for Sei

TL;DR: SIP-5 is the proposed post-quantum upgrade path for Sei. It is not an immediate plan, but rather a proposed way for the network to move to quantum-safe signatures before a quantum computer can break the cryptography that EVM accounts rely on today. Under SIP-5 every existing account keeps its address, balance, and history, and can bind a post-quantum key before a governance cutoff. We are shipping this defense now because today's post-quantum cryptography is still immature, and we are building better post-quantum cryptography in parallel.

Why a post-quantum upgrade path, and why now

SIP-5 is the initial proposed post-quantum upgrade path for the Sei Network. Its job is to give the network a secure route to becoming post-quantum before the threat it defends against actually arrives.

Every EVM account is secured by ECDSA over the secp256k1 curve. That signature scheme is what proves an account authorized a transaction. A sufficiently capable quantum computer running Shor's algorithm can recover a private key from its public key and forge those signatures. No such machine exists today, and estimates for when one might vary widely, but any real post-quantum response takes time to build and deploy. The goal of this plan is to give Sei a solution well before a threat makes it necessary.

Post-quantum cryptography is still immature. The post-quantum signature schemes available today are orders of magnitude bigger than an ECDSA signature, and that size will slow down EVM blockchains that adopt them. Beyond raw size, many pitfalls are hidden inside any migration: how accounts opt in, what happens to accounts that do not, and how the chain stays live through the switch. SIP-5 is designed to hold up against those pitfalls.

SIP-5 is also only one half of the work. In parallel, Sei Labs is developing new post-quantum cryptography aimed at delivering high performance and post-quantum security at the same time.

How the SIP-5 migration works

SIP-5 defines a migration path that preserves the account state that already exists. Every EVM address, balance, nonce, and contract relationship carries forward. There will be no chain-wide reset.

The mechanism turns on a single governance-set cutoff, a block height called H_Q, and one new operation.

SetPQKey is the operation an account uses to bind a post-quantum key to itself. Before H_Q, any address can call SetPQKey to register an ML-DSA key against its existing account. ML-DSA is the post-quantum digital signature scheme standardized by NIST, so the binding uses a vetted, standardized primitive.

Before H_Q, classical ECDSA signing still works, so accounts have a large window during which they can migrate. After H_Q, classical ECDSA authorization will be disabled across the network. From that point, originating a transaction will require a valid ML-DSA signature that matches the key the account registered. Because H_Q is set by governance rather than hardcoded, the network can bring the cutoff forward if circumstances change.

That gives accounts three ways through the transition:

  • Opt into post-quantum early. An account can move to post-quantum-only authorization ahead of H_Q.

  • Carry both through the window. An account can keep both classical and post-quantum signatures valid through the transition window.

  • Do nothing and reach H_Q unbound. An account that hits H_Q without registering a key enters invalid mode. It remains a valid recipient, funds can still be sent to it, but it can no longer originate transactions until it migrates.

Users will get enough time to migrate deliberately while the chain keeps a governance lever to move quickly if the threat arrives faster than anyone expects.

What SIP-5 does and does not claim

SIP-5 commits the network to a concrete migration mechanism today. It does not claim that today's post-quantum signatures are cheap, and it does not ask the network to accept their performance cost as permanent.

That is the reason the two efforts run together. SIP-5 makes the network defensible now with the standardized tools that exist today. The parallel cryptography research is aimed at making post-quantum security something the network can carry at full performance.

Read the full specification in the SIP below.

Sources