From CoinDesk · By Omkar Godbole
Coinbase says Bitcoin should begin preparing now for quantum computers that could eventually derive private keys from public keys and drain vulnerable wallets.
The exchange recommends flexible post-quantum signatures, staged adoption, reliable implementations and support for both individual users and institutions using multiparty security systems.
Coinbase says the contentious question of how to handle dormant or late-migrating wallets should be addressed separately so it does not delay broader protections.
What if someone builds a quantum computer fast enough to crack your bitcoin wallet's security and siphon off your coins?
That's on everyone's mind, since some projections suggest that such a quantum machine, though it doesn't exist today, could arrive within a few years.
Nasdaq-listed crypto exchange Coinbase COIN$181.88·Market Closed, which holds about 5% of all bitcoin in existence today for its clients, including banks, asset managers and hedge funds, has shared its thoughts on that question in a new blog post, laying out what it believes bitcoin needs to do to stay secure against a "potential future" quantum threat.
Its first point is to start preparing now, not wait for the risk to arrive, and handle the question of lost coins separately.
To follow the exchange's suggestions, it helps to know how Bitcoin's locks work and how a quantum computer can break them.
The lock and key
Think of a bitcoin wallet as a mailbox with a narrow horizontal slot at the top and a key held only by the owner. The visible slot, through which anyone can drop letters inside, is the wallet's public key. The private key, by contrast, is the physical key that unlocks the box. Kept strictly in the owner's hands, this private key is invisible to the outside world and keeps the Bitcoin in the wallet safe.
When a user sends bitcoin, their wallet uses the private key to create a digital signature, a tamper-proof stamp. The network checks it against the user's public key; if it matches, the transaction is approved.
The Bitcoin blockchain uses two methods, called ECDSA and Schnorr, to create and verify these digital signatures. These are extremely secure for now because current computers aren't powerful enough to crack the math behind these techniques and reverse-engineer a user's private key from its digital signature or public key.
Enter the quantum risk
A sufficiently powerful quantum computer, one that could exist by 2029, according to Google Researchers, could do just that: reverse-engineer a private key from a public key and drain holders' bitcoin wallets.
Researchers call a machine with that capability a cryptographically relevant quantum computer, or CRQC.