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<\/p>\n 19h05 \u25aa
\n 6
\n min read \u25aa by
\n Nicolas T.<\/p>\n
It is no longer if, but when. The quantum computer will soon be a reality, and it is time to take stock. How many bitcoins are currently at risk?<\/p>\n
<\/p>\n
In Brief<\/p>\n
ChainCode has calculated that 32.7% of BTC are currently vulnerable.
\n 6.36 million bitcoins are currently at risk.
\n 103 million utxos representing 4.49 million BTC are vulnerable due to address reuse.<\/p>\n
Bitcoin and Cryptography<\/p>\n
Recent advances by Google and Microsoft in quantum computing have evolved the consensus. Several BIPs are already on the table to address the threat.<\/p>\n
Don\u2019t miss our previous article about BIP-360<\/a>. You will find plenty of information on the subject there. Today\u2019s article focuses on the exact number of BTC currently vulnerable to the quantum threat. The figures come from the ChainCode Labs report<\/a> presented by Anthony Milton at the Quantum Bitcoin Summit.<\/p>\n Before the numbers, let\u2019s quickly review the cryptographic mechanisms of bitcoin. Let\u2019s start with Bitcoin addresses that are most familiar to us. These addresses are encodings of public keys, hence the term \u201cpublic key cryptography,\u201d also called \u201casymmetric cryptography.\u201d<\/p>\n These public keys are created from a private key commonly called the \u201cseed.\u201d That is, the 12 or 24 words generated when creating a wallet. These 12 words actually represent a large 128-bit number (plus a checksum) from which your wallet can derive billions of public keys (Bitcoin addresses).<\/p>\n Nowadays, \u201cpublic keys\u201d are not really public anymore. As mentioned above, they are hashed using quantum-resistant hashing functions RIPEMD-160 and especially SHA-256. The resulting hash is what we call a \u201cBitcoin address.\u201d<\/p>\n These addresses are used to build UTXOs (Unspent Transaction Outputs). This technical term refers to \u201cscripts\u201d (a piece of code) that lock an amount of BTC (a number) to a public key.<\/p>\n Each BTC transaction consumes and creates UTXOs simultaneously. There are currently about 170 million UTXOs.<\/p>\n The Unbreakable SHA-256<\/p>\n Wallets therefore do not actually contain bitcoins, but private and public keys. These keys are very large numbers linked by a \u201cone-way\u201d mathematical function. In other words, it is impossible for a classical computer to compute a private key from a public key.<\/p>\n The problem is that quantum computers could achieve this (thanks to Shor\u2019s algorithm). Sharp minds might say: \u201cSo what? No problem since we said addresses are encoded with the SHA-256 algorithm which is resistant to quantum computers.\u201d<\/p>\n Absolutely. A public key concealed behind a SHA-256 encoding is safe, no matter what. However, making a transaction necessarily reveals the public key associated with the UTXO being spent.<\/p>\n After this transaction, the public key is known to everyone. Therefore, the address in question should no longer be reused to receive new BTC. Unfortunately, many addresses are reused.<\/p>\n Added to these reused addresses are the addresses of the very first types of UTXOs which were simply public keys without any encoding. This type of script is called P2PK (Pay-to-Public-Key). And finally, the spent P2TR (Pay-to-TAPROOT) UTXOs.<\/p>\n Altogether, ChainCode calculated that 32.7% of BTC are currently vulnerable. That is about 6.36 million bitcoins. Of this total, 69% (103 million UTXOs representing 4.49 million BTC) are vulnerable due to address reuse.<\/p>\n The rest mainly consists of P2PK-type UTXOs (1.87 million BTC), or 8.65% of BTC in circulation. And P2TR UTXOs (0.15 million BTC).<\/p>\n Are Your Bitcoins in Danger?<\/p>\n Yes, if you have reused an address after using it for a transaction. Also yes if you participated in the \u201cordinals\u201d trend and other inscriptions that mostly use P2TR UTXOs. However, these UTXOs contain very few BTC.<\/p>\n
Yes, if your addresses are of the P2PK type. There is, however, little chance this is the case if you installed your wallet after 2011.<\/p>\n
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