Puzzle 2

23rd January

19:00 UTC

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A good rogue must be able to complete the obstacle course within a specific amount of time.

View the solution

Puzzle Preparation

To give you a better chance of solving this puzzle, we suggest that you look through some relevant background materials.

See puzzle details on Github

Puzzle link

Puzzle Hints

1. Read about rogue key attacks. The following paper is a good resource:

2. Note that the proof-of-possession scheme is not exactly the one done in Sapling... observe the differences

3. Use the fact that proof-of-possession scheme is malleable to generate a proof for a key you don't know the discrete log for - one that cancels out the contribution of the other keys

Puzzle Winners

gold 01


Puzzles completed



silver 02


Puzzles completed



bronze 03


Puzzles completed



You can see all of the scores for this puzzle in the spreadsheet here.

Puzzle Solutions and Write-ups

The winner of the puzzle write up was submitted by thor314. You can view the solution and puzzle write up here. The background material required to solve the puzzle is also covered in the write up.
There were many interesting write-up submissions which are linked below:
* Write-up by thor314
* Write-up by niooss-ledger
* Write-up by sylvainpelissier
* Write-up by 10to4
* Write-up by flyq
* Write-up by huy-tn
* Write-up by 0xArsi
* Write-up by Megaloblastt
* Write-up by notnotraju
* Write-up by timgestson
* Write-up by TrapdoorHeader