In a police lineup, the suspect stands beside fifteen strangers who look like him, and a witness picks. It only protects him while the strangers stay convincing and nobody gets to run it twice.
That lineup is how Monero, the biggest privacy coin, hides who paid whom. A privacy coin is digital money built so outsiders cannot see the sender, the receiver or the amount. Every Monero payment goes into a public record, one block every two minutes, and each one stands in a lineup with 15 decoys pulled from older payments. Computers compete to write each block, which is called mining, and whoever holds the most computing power writes it most often.
My claim: twice since March 2024, someone thinned that lineup without breaking any math, and I think the privacy is already gone for anyone who needs it to hold when somebody pushes.
March 2024. A spammer flooded the record for 23 days for about 80 XMR, Monero's own coin, in fees. The best public estimate put the working lineup at 5.5 faces instead of 16, since he could rule out his own decoys.
August 2025. A mining group announced it had passed half of Monero's computing power. Researchers found no proof it held that for long.
September 14, 2025. Someone with enough power rewrote 18 blocks, about 70 minutes, when Monero's own rule calls ten blocks safe. 115 payments already written in were thrown out and re-sent, and a re-sent payment draws a fresh lineup. Put the old lineup beside the new one and the one face in both is the real payer. That happened to about 74 percent of them, and it cannot be undone.
The strongest case for Monero is fair. On a quiet day it hides more than Bitcoin, which shows sender, receiver and amount to anyone who looks. No coins were lost in the rewrite and no shop has publicly reported a loss. The developers are building a replacement that hides each payment among every payment ever made, with no launch date as of August 2026.
What would prove me wrong: twelve months with no rewrite deeper than ten blocks and a working lineup back near 16.
Bitcoin never promised a lineup, so a rewrite has nothing to expose, and its privacy tools sit on top of the record. That record is guarded by about 900 billion billion guesses a second from machines built for one job. Monero's has about 6 billion, from ordinary computer chips. Bitcoin's two block rewrite on March 24 this year was rare enough to make the news. I would rather build privacy on a record that has held than trust a lineup two strangers have walked through.
if this changed how you judge a privacy promise, Zap ⚡