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1  Other / Meta / What about an Announcements forum for Altcoins? on: June 08, 2014, 06:47:41 AM
Yes, I KNOW there's already a forum with the misleading name "Announcements (Altcoins)", but that one is mainly used for discussing announcements of altcoins, e.g. I'm pretty sure the 36068 postings about Darkcoin do not ALL have announcing content.

Have 20 of those high-traffic-announcement threads and _real_ announcements will never show up anywhere near page one.

My proposal, open for discussion of course, would be:

  • Announcements (Altcoins): only ONE posting per thread, no follow-ups allowed, with a moderator who closely watches abuse.
  • Announcements (Discussion): renamed version of  the currently existing one.

Thoughts?

2  Alternate cryptocurrencies / Altcoin Discussion / Darkcoin paranoia? on: May 28, 2014, 07:50:53 AM




Out of nowhere unknown (big) pools and hash-rate doubling to 190 GH/s in just one day...if I would plan an attack I would it do right after a long announced fork  Shocked
3  Bitcoin / Development & Technical Discussion / What if a block can NEVER be found? on: May 01, 2014, 09:54:49 AM
Disclaimer: I'm a complete crypto-currency noob, and besides doing some alt-coin mining for 3 months now I never had the slightest idea what's behind all this.

Not until I've read Satoshi's whitepaper last week.

After letting it settle for some days, and a closer look into the algorithm and source code, I think I might have found a problem which _could_ have serious implications.

I barely scrapped the surface of this all, so if you think I'm wrong either because I'm just dumb or lacking some knowledge feel free to say so, and preferably point me to additional information/papers for further reading.
Most probably someone else has already pointed this out years ago and I just could not find that information.


Anyway, from what I have read a block header is the hash of the version, previous block, Merkle root, time stamp, difficulty (short VPMTD+N because I don't want to write this again  Grin ) and a variable nonce chosen in a way that the resulting hash has the needed number of leading zero bits to fulfill the difficulty criterion.

Since VPMTD is fixed for a given block and SHA256 is a deterministic function the number of possible hashes is finite because the number of nonces is finite (uint32_t possibilities), in other words not all _possible_ hashes exist, just a finite subset.

Therefore it _could_ be that for this given finite set of inputs there is no hash which has the required number of leading zero bits.

VERY improbable, but not impossible.

In this case there would be no next block and the complete block-chain would come to a halt.
So would Bitcoin and a multimillion crypto economy.

Or is (what I would do) there already some heuristic which detects an unusual long block-time (e.g. longer than the difficulty re-target time) and changes the input (if I remember correctly there are some padding bits which could be abused for this, or just change the difficulty which is also part of the hash) to prevent this?

Or am I just the next noob who asks this dumb question?

A curious mind....
4  Alternate cryptocurrencies / Altcoin Discussion / Is this a Dogecoin fork attempt? on: April 21, 2014, 12:02:00 PM
[Disclaimer: this is the first time I've investigated into the depths of a blockchain, so if I should have understood this completely wrong please correct me! If you need more data from my log, request it, I'm happy to help]


3 days ago I started my Dogecoin wallet (the latest 1.6.something version, downloaded from the official Dogecoin link) after being offline for 2 days and it stopped syncing at block 186741.

What I tried so far:

  • Re-installed the wallet, and using only the nodes listed on the official Dogecoin announcement page here in this forum
  • Restored blockchain from a 6 week old local backup
  • Completely synced blockchain from scratch into the empty Dogecoin folder

But, no matter what, sync stopped at block 186741.

Fortunately I have a debug.log for this time, this is what it says:

Code:
2014-04-20 18:45:55 received block d8768862a5cc5ddd786232982985a92122ce3159848a878a17fb966f207d5e6d
2014-04-20 18:45:55   nActualTimespan = 23  before bounds
2014-04-20 18:45:55 DIGISHIELD RETARGET
2014-04-20 18:45:55 GetNextWorkRequired RETARGET
2014-04-20 18:45:55 nTargetTimespan = 60    nActualTimespan = 56
2014-04-20 18:45:55 Before: 1b393006  0000000000393006000000000000000000000000000000000000000000000000
2014-04-20 18:45:55 After:  1b356005  0000000000356005999999999999999999999999999999999999999999999999
2014-04-20 18:45:55 SetBestChain: new best=d8768862a5cc5ddd786232982985a92122ce3159848a878a17fb966f207d5e6d  height=186741  log2_work=59.243471  tx=9278894  date=2014-04-18 16:32:14 progress=0.997577
2014-04-20 18:45:55 ProcessBlock: ACCEPTED
2014-04-20 18:45:56 received block 42baadc93c3b503e06d28ecdc225fd48eea3a237fce7926359f871bffe776662
2014-04-20 18:45:56   nActualTimespan = 79  before bounds
2014-04-20 18:45:56 DIGISHIELD RETARGET
2014-04-20 18:45:56 GetNextWorkRequired RETARGET
2014-04-20 18:45:56 nTargetTimespan = 60    nActualTimespan = 62
2014-04-20 18:45:56 Before: 1b356005  0000000000356005000000000000000000000000000000000000000000000000
2014-04-20 18:45:56 After:  1b37277c  000000000037277ca22222222222222222222222222222222222222222222222
2014-04-20 18:45:56 ERROR: ConnectBlock() : inputs missing/spent
2014-04-20 18:45:56 InvalidChainFound: invalid block=42baadc93c3b503e06d28ecdc225fd48eea3a237fce7926359f871bffe776662  height=186742  log2_work=59.243482  date=2014-04-18 16:36:39
2014-04-20 18:45:56 InvalidChainFound:  current best=d8768862a5cc5ddd786232982985a92122ce3159848a878a17fb966f207d5e6d  height=186741  log2_work=59.243471  date=2014-04-18 16:32:14
2014-04-20 18:45:56 InvalidChainFound: invalid block=42baadc93c3b503e06d28ecdc225fd48eea3a237fce7926359f871bffe776662  height=186742  log2_work=59.243482  date=2014-04-18 16:36:39
2014-04-20 18:45:56 InvalidChainFound:  current best=d8768862a5cc5ddd786232982985a92122ce3159848a878a17fb966f207d5e6d  height=186741  log2_work=59.243471  date=2014-04-18 16:32:14
2014-04-20 18:45:56 ERROR: SetBestBlock() : ConnectBlock 42baadc93c3b503e06d28ecdc225fd48eea3a237fce7926359f871bffe776662 failed
2014-04-20 18:45:56 ERROR: AcceptBlock() : AddToBlockIndex failed
2014-04-20 18:45:56 ERROR: ProcessBlock() : AcceptBlock FAILED
2014-04-20 18:45:56 Misbehaving: 69.245.81.106:22556 (0 -> 100) DISCONNECTING
2014-04-20 18:45:56 disconnecting node 69.245.81.106:22556

Does this "misbehaving" node 69.245.81.106 try to manipulate things or is it normal that clients are misbehaving due lack of programming skills?

After this, I got a couple of hundreds "received block ...", "Process block: ORPHAN BLOCK, ...." message pairs.

After that, for each(!) incoming new block I get:
Code:
2014-04-20 18:47:29 received block 5ca10c212bf91a77fac7fa181574d97b2b2b238ae57aa2b37ba9aa149c1c3c62
2014-04-20 18:47:29   nActualTimespan = 265  before bounds
2014-04-20 18:47:29 DIGISHIELD RETARGET
2014-04-20 18:47:29 GetNextWorkRequired RETARGET
2014-04-20 18:47:29 nTargetTimespan = 60    nActualTimespan = 85
2014-04-20 18:47:29 Before: 1b37277c  000000000037277c000000000000000000000000000000000000000000000000
2014-04-20 18:47:29 After:  1b4e229a  00000000004e229a555555555555555555555555555555555555555555555555
2014-04-20 18:47:29 InvalidChainFound: invalid block=5ca10c212bf91a77fac7fa181574d97b2b2b238ae57aa2b37ba9aa149c1c3c62  height=186743  log2_work=59.243489  date=2014-04-18 16:37:51
2014-04-20 18:47:29 InvalidChainFound:  current best=d8768862a5cc5ddd786232982985a92122ce3159848a878a17fb966f207d5e6d  height=186741  log2_work=59.243471  date=2014-04-18 16:32:14
2014-04-20 18:47:31 InvalidChainFound: Warning: Displayed transactions may not be correct! You may need to upgrade, or other nodes may need to upgrade.
2014-04-20 18:47:29 ProcessBlock: ACCEPTED

The "Displayed transactions may not be correct..." message is also displayed within the wallet.

I've never seen this this with any coin before. Is this normal, should I be worried and most important, how can I stop/work around this to sync my wallet again?


Any help highly appreciated!

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