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Congratulations Capture the Coin participants!

By Author


, September 17, 2019

, 3 min read time

We are pleased to announce the completion of our Blockchain Security competition — Capture the Coin. Our mission was to promote the field of blockchain security and educate players in the areas of cryptography, smart contracts, forensic analysis, malware, and others. We are excited that so many of you participated and hopefully inspired to join the good fight to make the future open financial system safer for all.


The prize for all of the top contest participants is a custom laser etched steel wallet. In case you are not familiar, steel wallets can be used to backup the mnemonic seeds used to unlock all of the cryptocurrency wallets such as Coinbase Wallet.


We had eight players who completed all of the challenges. We will be reaching out to each of them with prize information shortly:

1. arpox 2. Gundas 3. Verichains 4. Captura 5. Starkat 6. Kubertu 7. mofa28 8. drdr

In addition, congratulations to the four winners at Defcon 27 — Blockchain Village:

1. philip 2. ConsenSysDilligence 3. Skynet404 4. Lollerk8s

Really good job, folks!


Our challenges were split into three categories: Trivia, Blockchain, and Cryptography. They covered a wide range of topics ranging from blockchain forensics, smart contract security, cryptocurrency-stealing malware, and various cryptography flaws. We would like to thank the many challenge creators and platform maintainers:

  • Capture the Coin Infrastructure — Nishil Shah

  • Trivia challenges — Zassmin Montes de Oca and Peter Kacherginsky

  • Blockchain: Satoshi’s Secret — Mark Nesbitt

  • Blockchain: Hide and Seek — Peter Kacherginsky

  • Blockchain: Evil Droid — Joel Kenny

  • Blockchain: Daily Double…spend — Don Yu

  • Blockchain: Tricky Ether — Peter Kacherginsky

  • Cryptography: AES Encryption Flaw — Jake Craige

  • Cryptography: ECDSA Nonce Reuse — Jake Craige

  • Cryptography: Linkable Payments — Max Mikhaylov

  • Cryptography: Schnorrer Signature — Jesse Posner

  • Cryptography: Forging a Signature — Jake Craige

Also special thanks to Dom Flask for the awesome prize design and many others at Coinbase who helped make this contest happen!


The contest had 438 registered users and 154 active participants both online and during Defcon 27’s Blockchain Village.

Out of the 22 challenges, cryptography category had the least amount of solves and trivia the most. Our hardest cryptography challenge, Linkable Payments, had only 11 solves and our easiest challenge, Satoshi, had 136 solves.


The majority of players with solutions came from the US, followed by Singapore, France, UK, and other countries in Europe.

We hope you enjoyed the contest and looking forward to seeing you all next year for another installment of Capture the Coin. But for now, look out for the upcoming blog series where we will cover challenge solutions and the behind the scenes look on our CTF infrastructure.

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