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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Mar 12, 2025