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Bitcoin has no clock. Miners write the time into each block themselves. One line in Satoshi’s 2009 code lets a miner with most of the hash rate lie about it and cut the difficulty window after window. With all of it: the minimum in about 39 days.

Checked it against daily closes. True, so far: 2011: -92.7% 2013-15: -84.5% 2017-18: -83.8% 2021-22: -76.7% 2025-26: -53.1%, still open Odd detail: -53.1% is exactly how deep the summer 2021 dip went, and that one hit a new high three months later.

Today, moving coins to a fresh address is the best quantum defense you have. After a quantum computer shows up, moving them is the risk. Spending puts your public key in the mempool until the next block, and Google’s March paper put cracking one key at about 9 minutes.

Bitcoin turns 18 today. Satoshi sent out the whitepaper on Halloween, 2008. Fitting, because it’s been buried at least 477 times since. Every tombstone in this video is a real obituary, dropped in the year it ran. Watch where they pile up. Hint: not at the bottoms.

Multisig in 35 seconds. Three keys from three different makers, any two sign. Lose one, spend with the other two. Steal one, steal nothing. A bug in one brand breaks nothing. The part people skip: back up the wallet descriptor. Without it, two seeds can’t find the coins.

Binance says it will cover all $6.3B of yesterday’s hack from its own funds. Good for its customers. Not every custodian could. Here are the ones that couldn’t. Binance paused withdrawals after the hack. Coins on your own keys don’t have a pause button.

“Put a fork in it. It’s done.” @PeterSchiff, March 2020. Bitcoin was $7,896. He’s been writing bitcoin’s obituary for 13 years, so we put all 11 of his dated calls on one chart. Bitcoin is still here. The awkward part: his last two calls are holding up.

New on LearnBitcoin: the bitcoin-dev mailing list, readable. Fifteen years of the list where Bitcoin's rules get argued over, one page per thread, searchable, updated daily. 24,699 messages, 3,292 threads, 1,419 people, June 2011 to this week. learnbitcoin.com/archive

New chapter: Which Coins Does Your Wallet Spend? Your wallet has no balance. It has a bag of coins, and every payment starts by picking which to spend. What the pick costs now and later, what it tells a chain analyst, and how Bitcoin Core decides. learnbitcoin.com/rabbit-hole…

We brute-forced two vanity addresses on a laptop CPU this week. 1LearnBTC, any letter case: 46 minutes. bc1qlearn8tc: 6 hours 1 minute. Same eight chosen characters. Bech32 has no upper or lower case to lean on, so the average job was 2.7x bigger. Luck did the rest.

@adam3us @alistairmilne

Half of the top 20 largest quantum-exposed bitcoin addresses belong to exchanges and custodians, holding ~1.06M BTC learnbitcoin.com/rabbit-hole…

35% of all bitcoin (7.1M BTC) sits where its public key is already visible on-chain. @drakefjustin's "bunker mode" advice fixes most of it: 5.2M of that is exposed only because an address got reused. Move it to a fresh bc1q address and the key is hidden again. The other 1.9M is exposed by design: early pay-to-pubkey coins and Taproot.

Bitcoin's entire security model is that rewriting history costs more than anyone can profitably spend.

The 60-second version, now on YouTube: youtu.be/5CX5XATmQR4

Alice sends Bob 0.1 BTC. What actually happens between "Send" and "Confirmed"? Forty-eight seconds. Every step. learnbitcoin.com/journey/usi…

Multisig in 35 seconds. Three keys. Any two sign. Lose one. Spend with the other two. Steal one. Steal nothing. learnbitcoin.com/glossary/mu… #Bitcoin

The mempool isn't a queue. Every node has its own. Transactions sort by fee rate, not arrival time. Pay the rate. Or wait. Or rebroadcast. learnbitcoin.com/rabbit-hole… #Bitcoin