Trying to understand double spending after 1 confirmation.

[o_e_l_e_o]

I tried, but got different numbers. How did you calculate this?

Those two particular examples I simply lifted from page 8 of the the whitepaper. For q=0.3 (an attacker with 30% of the hashrate), the probability (P) they overturn 10 confirmations (z=10) is 0.0416605, which is 4.16605%.

The equation itself is also given in the whitepaper, but rather than calculate it manually you can just plug your numbers in here: https://web.archive.org/web/20181231045818/https://people.xiph.org/~greg/attack_success.html

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[tranthidung]

Loyce,

You can check it with Lopp's Bitcoin confirmation risk calculator too
https://jlopp.github.io/bitcoin-confirmation-risk-calculator/
https://github.com/jlopp/bitcoin-confirmation-risk-calculator

Lopp has an account in Bitcointalk and replied when he fixed a bug in his tool.

The rounding error was an unintentional result of me taking the form input and running it through parseInt, which truncates all decimal precision. I've changed that to parseFloat - the discrepancy is now resolved.