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Capture the flag

You need to capture the flag, or rather to put Ether in the Flag contract without a Thief taking it before you can claim the flag.

Goals

  • The exercise serves to show that not all Ether comes with a beautiful transaction.
  • It also serves to show that if you forgot to make your operations atomic, someone may exploit it by sneaking in between your operations.
  • Accessorily it shows the power of gas price.

Notes

  • You need to run the node/watchAndSteal.js trap for the challenge to be fun.
  • The Thief contract is not strictly needed, it is only here so that the capture call happens in an internal transaction, and as such is semi-invisible on Etherscan.
  • The sneakUpOn function is totally useless and acts as a decoy. Do not remove it.

When deploying the IPFS page, you need to adjust, manually?, for ./static and ../../fonts.

Current IPFS location: http://ipfs.b9lab.com:8080/ipfs/QmNidcNaGnresM8EFhU5J3gWV9Sfan5CX3qwcTfruNJN8x/