UNunbeli·Mar 7, 2017
I think that won't even compile due to an accidentally pasted URL here:
https://github.com/zcoinofficial/zcoin/commit/0359bcb2ead7fe...
In Zcoin implementation bug enabled attacker to create over 500K Zcoinsfiroorg
firo
C++2017–2017
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firo
The privacy-focused cryptocurrency
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This week on Hacker News
Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 3:03:16 PM UTC.
No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.
Mentions over time
HN mentions by day10 dated mentions
Observed mentions: 2017-02-17 22:48:14 UTC to 2017-03-07 09:42:18 UTC.
Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.
View mention counts and date ranges
| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
|---|---|---|---|---|---|
| Feb 17 | 2017-02-17 00:00:00 UTC | 2017-02-18 00:00:00 UTC | 2 | 0 | 2 |
| Feb 18 | 2017-02-18 00:00:00 UTC | 2017-02-19 00:00:00 UTC | 5 | 0 | 5 |
| Feb 19 | 2017-02-19 00:00:00 UTC | 2017-02-20 00:00:00 UTC | 0 | 0 | 0 |
| Feb 20 | 2017-02-20 00:00:00 UTC | 2017-02-21 00:00:00 UTC | 0 | 0 | 0 |
| Feb 21 | 2017-02-21 00:00:00 UTC | 2017-02-22 00:00:00 UTC | 0 | 0 | 0 |
| Feb 22 | 2017-02-22 00:00:00 UTC | 2017-02-23 00:00:00 UTC | 0 | 0 | 0 |
| Feb 23 | 2017-02-23 00:00:00 UTC | 2017-02-24 00:00:00 UTC | 0 | 0 | 0 |
| Feb 24 | 2017-02-24 00:00:00 UTC | 2017-02-25 00:00:00 UTC | 0 | 0 | 0 |
| Feb 25 | 2017-02-25 00:00:00 UTC | 2017-02-26 00:00:00 UTC | 0 | 0 | 0 |
| Feb 26 | 2017-02-26 00:00:00 UTC | 2017-02-27 00:00:00 UTC | 0 | 0 | 0 |
| Feb 27 | 2017-02-27 00:00:00 UTC | 2017-02-28 00:00:00 UTC | 0 | 0 | 0 |
| Feb 28 | 2017-02-28 00:00:00 UTC | 2017-03-01 00:00:00 UTC | 0 | 0 | 0 |
| Mar 1 | 2017-03-01 00:00:00 UTC | 2017-03-02 00:00:00 UTC | 0 | 0 | 0 |
| Mar 2 | 2017-03-02 00:00:00 UTC | 2017-03-03 00:00:00 UTC | 0 | 0 | 0 |
| Mar 3 | 2017-03-03 00:00:00 UTC | 2017-03-04 00:00:00 UTC | 0 | 0 | 0 |
| Mar 4 | 2017-03-04 00:00:00 UTC | 2017-03-05 00:00:00 UTC | 0 | 0 | 0 |
| Mar 5 | 2017-03-05 00:00:00 UTC | 2017-03-06 00:00:00 UTC | 0 | 0 | 0 |
| Mar 6 | 2017-03-06 00:00:00 UTC | 2017-03-07 00:00:00 UTC | 0 | 0 | 0 |
| Mar 7 | 2017-03-07 00:00:00 UTC | 2017-03-08 00:00:00 UTC | 3 | 0 | 3 |
What Hacker News says
10 sourcesThe commit that fixes it does not change any tests:
https://github.com/zcoinofficial/zcoin/commit/0359bcb2ead7fe...
This indicates that the code in question is not covered by tests. I work on a database, for which correctness is paramount, so it's unnerving to see any code fixes not associated with test additions or changes. I would have thought that cryptocurrency had similar standards.
In Zcoin implementation bug enabled attacker to create over 500K ZcoinsThe error is here:
https://github.com/zcoinofficial/zcoin/blob/81a667867b5d8489...
and the line of code:
zccoinSpend.denomination == libzerocoin::ZQ_LOVELACE;
In other words, a statement with no effect. In D, such a line gives an error, not a warning:
Error: == has no effect in expression
You can force the statement to be accepted by casting it to void.
It's really past time for languages to not accept such code any more. Legacy code needs to get fixed.
In Zcoin implementation bug enabled attacker to create over 500K ZcoinsI think the single character fix is this [1], GP seems to be describing [2].
[1] https://github.com/zcoinofficial/zcoin/commit/b20c177032de3c...
[2] https://github.com/zcoinofficial/zcoin/commit/33796c839f7d4d...
In Zerocoin implementation bugwhat went wrong: TLDR probably Ctrl-C,Ctrl-V.
(Just to be clear, this is about Zcoin, not Zcash/Zerocash. The two are completely different)
The fix is here. https://github.com/zcoinofficial/zcoin/commit/33796c839f7d4d...
What happened?
First, some stylized facts about ZCoin:
0) ZCoin is a fork of Bitcoin that uses a 4 year old academic research library, libzerocoin, to make anonymous payments using the Zerocoin protocol.
1) Unlike Zcash/Zerocash, the Zerocoin protocol has only fixed value coins.
2) To get multiple denominations, you have completely separate instances of the anonymous currency that just happen to live on the same blockchain as the other denominations.
3) Zerocoin has its own bitcoin like non anonymous base currency. Call it basecoin.
4) You spend basecoins to get zerocoins.
5) When you spend zerocoins, you get basecoins.
6
Read the rest
) ZQ_WILLIAMSON and ZQ_PEDERSEN are denominations, worth 100 and 50 respectively, defined in libzerocoin.
So what went wrong?
When you convert a zerocoin into 100 basecoin, the ZCoin code forked from bitcoin checked if the coin was a valid instance of ZQ_PEDERSEN (worth 50 ) not ZQ_WILLIAMSON (worth 100). So you paid 50 for the zcoin,got it into the instance for ZQ_PEDERSEN, but got back 100. Free money.
Why did this happen? Well, it looks like in order to support the multiple denominations libzerocoin offers, the ZCoin developers wrote some code for one denomination and then duplicated it for each remaining denomination. There are five in total, ZQ_LOVELACE=1,ZQ_GOLDWASSER=10, ZQ_RACKOFF = 25, ZQ_PEDERSEN = 50,ZQ_WILLIAMSON = 100.
But on the last one, ZQ_PEDERSEN was not changed to ZQ_WILLIAMSON in a few places. This caused the bug.
Caveat: I have nothing to do with ZCoin. However, I am an author of the zerocoin protocol, libzerocoin, the zerocash protocol, and am involved with Zcash.
Nope this -- 4 commits later, and 12 minutes ago at this time.
https://github.com/zcoinofficial/zcoin/commit/b20c177032de3c...
In Zerocoin implementation bugYeah that seems quite possible.
(And people mock me for putting constants first!
i.e.
if (someconstant == somevar) { ...
[edit: nope, looks like this is it]
https://github.com/zcoinofficial/zcoin/commit/b20c177032de3c...
In Zerocoin implementation bugActually I think this might have been the fix.
https://github.com/zcoinofficial/zcoin/commit/584e1c60617d59...
In Zerocoin implementation bugBetter look at commits.
I am not familiar with their code base, but latest commit seems like a bugfix: https://github.com/zcoinofficial/zcoin/commit/33796c839f7d4d...
In Zerocoin implementation bugAnyone know which line of code they're talking about?
I took a glance at their Github bug tracker and couldn't find any references to this bug.
[0] https://github.com/zcoinofficial/zcoin/issues?q=is%3Aissue+i...
In Zerocoin implementation bug