quizchain/18

Solved on 2019-04-10 after 4h 59m, key derived from the published recipe. 0.007 BTC on Bitcoin.

Story

What the post asked, what the answer turned out to be, and what the chain says happened. The record below holds the data.

Kerckhoffs

Start with offs and add the missing letters. The author dripped the rest out letter by letter on Twitter.

It's Kerckhoffs, of the principle that a cipher must not depend on a secret method. The author's point: nearly every block in this chain survives only because the method is secret. A little self-aware, that one. Five hours.

IDquizchain/1818 / 772019-04-10

Puzzle / quizchain

18

bitcoinp2pkh solved

Record

bitcoinPuzzle({
  address: p2pkh("16Cn1vy7wEGz…n856Myn5", "3912c8310f99…551aecae"),
  status: Status.Solved,
  key: wif("L2nS1Af6BM2C…gJVPqmEf").entropy("8c4705387f72…ba7bfaa1", source("https://www.…lock_18/")).derived(),
})

Prize: 0.007 BTC
Key material: wif, derived from the recipe
Verification: verified
Solved: 2019-04-10 · 4h 59m

tx 2

Trail: Explorerblockstream.info; Sourcereddit.com/r/bitcoinpuzzles/comments/bbij0e/meidum_7_mbtc_quizchain_block_18; Tryquizchain/18 in the playground

Address: 16Cn1vy7wEGzy3TWgwCzrcLd91n856Myn5

hash160 3912c8310f999eaa93c474ee6d8045c1551aecae

Balance

asking the explorer

Key

public key · compressed: 0226e59a96172e92b7d4a2010b32dd6589b13392dddeb8eb368487cac852db1afd
WIF: L2nS1Af6BM2C8PUe442nLWf7fBNK4q25k1thY4G9onLdgJVPqmEf
entropy hash: 8c4705387f72118d9518c6f0ba7bfaa1
entropy source: MD5 of the name, a space and the last three characters of the block 17 key

Transactions

funding2019-04-100.007 BTCf299d6796c…eecabf
claim2019-04-100.00679777 BTC8df3586b2b…b582b8

Hints

undated
officialQuestion: Start with "offs". Add the missing letters to get the solution string. Format: [solution] [link]. with exactly one space between them. Use MD5 as hash algorithm (changed from SHA 256 for all blocks after 15).
Sourcereddit.com/r/bitcoinpuzzles/comments/bbij0e/meidum_7_mbtc_quizchain_block_18
Published answer
Kerckhoffs
Sourcereddit.com/r/bitcoinpuzzles/comments/bbij0e/meidum_7_mbtc_quizchain_block_18
undated
officialThere are no letters in between, but these four may be at any position in the solution string. As I mentioned in my Twitter feed @NakamotoAoi, another letter is e, the only other vowel.
Sourcereddit.com/r/bitcoinpuzzles/comments/bbij0e/comment/ekjcc1k