What does post-quantum mean?

It describes cryptography meant to remain secure against an attacker with a large quantum computer. The threat is to public-key schemes, where a secret key could be recovered from the public one; symmetric encryption and hashing are far less affected.

What does PQC stand for?

Post-quantum cryptography. It names the replacement algorithms, most commonly lattice-based or hash-based, and in practice also the migration of systems already in service.

Why migrate before quantum computers exist?

Because data captured now can be decrypted later, so long-lived secrets are exposed from today. On public chains the exposure is already visible: the Quantum Alliance puts 6.4 million bitcoin, 30.2 percent of supply, in addresses whose public keys are on chain.

Post-quantum

Also: Post-quantum cryptography · PQC

Cryptography chosen to stay secure against an adversary holding a large quantum computer, and the migration problem that choice creates for systems already running.

The threat is specific rather than general. A sufficiently capable quantum computer would break the public-key cryptography used to agree keys and verify signatures, because it could recover a secret key from the public one. Symmetric encryption and hash functions are far less affected. Post-quantum cryptography replaces the vulnerable part, most often with lattice-based or hash-based constructions.

Why the deadline is already here

Data captured today can be decrypted later, which puts long-lived secrets at risk now rather than when the machine arrives. On public chains the exposure is sharper: the Quantum Alliance estimates that 6.4 million bitcoin, or 30.2 percent of supply, sit in addresses whose public keys are already visible, including about 1.1 million attributed to Satoshi Nakamoto. Those coins cannot be taken this way today, because no existing machine can do it.

What migrating actually involves

More than swapping an algorithm. A post-quantum proof-native protocol we covered drew the lesson plainly: changing signatures is not the same as securing a system end to end, and the hash choice determines proof size, recursion cost and bandwidth. Several folding schemes now aim at plausible post-quantum security through lattice assumptions while trying not to give up small fields or low recursion overhead.

Questions

What does post-quantum mean?: It describes cryptography meant to remain secure against an attacker with a large quantum computer. The threat is to public-key schemes, where a secret key could be recovered from the public one; symmetric encryption and hashing are far less affected.
What does PQC stand for?: Post-quantum cryptography. It names the replacement algorithms, most commonly lattice-based or hash-based, and in practice also the migration of systems already in service.
Why migrate before quantum computers exist?: Because data captured now can be decrypted later, so long-lived secrets are exposed from today. On public chains the exposure is already visible: the Quantum Alliance puts 6.4 million bitcoin, 30.2 percent of supply, in addresses whose public keys are on chain.

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