01
A large enough quantum computer, and today’s public keys
TLS and certificates lean on public-key algorithms: RSA, and elliptic-curve algorithms such as ECDSA and X25519. Their security is the difficulty of certain math problems for ordinary computers.
Shor’s algorithm is a quantum algorithm aimed at those problems. With a large enough quantum computer, it can recover a private key from the matching public key for the algorithms in wide use today. That is a property of the algorithm, not a label on an exchange.
Nobody knows when a machine of that size will exist. The planning starts from the algorithms you can already see.
02
Harvest now, decrypt later
A TLS session can be recorded today. If the key exchange was quantum-vulnerable, a large enough quantum computer could decrypt that recording later.
Signatures work on a different clock. A certificate is checked when someone presents it. Keys that stay in use for years are the ones a migration plan has to name.
03
Lattices, ML-KEM and ML-DSA
Post-quantum cryptography replaces those public-key problems with different ones. The standards in view here are lattice-based.
ML-KEM, FIPS 203, is how two parties agree a shared secret. ML-DSA, FIPS 204, is a signature. A picture of a lattice is a grid of points: the public key hides a secret path through that grid.
Hybrid TLS keeps a classical group and adds ML-KEM. X25519MLKEM768 is one such group: X25519 beside ML-KEM.
NIST IR 8547, Transition to Post-Quantum Cryptography Standards, was published in final form in October 2026 (https://csrc.nist.gov/pubs/ir/8547/final). It states that NIST will deprecate quantum-vulnerable public-key algorithms after 2030 and disallow them under NIST standards and guidelines after 2035.
04
What an exchange actually publishes
An exchange shows the world a website and a set of APIs. Each name completes a TLS handshake. The handshake has a protocol, a key-exchange group and a certificate algorithm.
The certificate is the long-lived piece. Signing keys behind withdrawals and internal approvals live longer still. A migration plan names those algorithms one by one.
05
Where Scan fits
Scan looks at the public endpoints an exchange lists. It writes down the protocol, the key-exchange group and the certificate algorithm, then turns that list into a migration checklist and a CycloneDX CBOM.
The goal is simple: find where the public cryptography is quantum-vulnerable, so the team can plan the move to post-quantum cryptography.