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Support Desk

Mike Feb 20 Announcements / Announcements

Dear MtGox Customers,

 

Thank you for your patience this week while we are working on re-initiating bitcoin withdrawals. In addition to the technical issue, this week we have experienced some security problems, and as a result we had to relocate MtGox to our previous office building in Shibuya (details can be found here: https://support.mtgox.com/home). The move, combined with some other security and technical challenges, pushed back our progress.

 

As much as we didn’t want to only provide an “update on an update”, this is the current status. We are committed to solving this issue and will provide more information as soon as possible to keep everyone in the loop.

 

We are very sorry for the delays and deeply appreciate your kind understanding and continuous support.

 

Best regards,

 

MtGox Team

Mike Feb 19 Announcements / Announcements

Dear MtGox Customers,

MtGox Co.,Ltd. (Japan) has moved to the address below:

MtGox Co.,Ltd.
Cerulean Tower 15F
26­-1 Sakuragaoka­cho
150­8512 Shibuya Tokyo
Japan

Please send all documents/letters to the above address from now on.
Thank you for your kind cooperation.

Best Regards,

MtGox Team

Mike Feb 17 Announcements / Announcements

February 17th, 2014


Dear MtGox Customers,


We apologize for the inconvenience caused by the recent suspension of external bitcoin transfers. Fortunately, as we announced on Saturday we have now implemented a solution that should enable withdrawals and mitigate any issues caused by transaction malleability (please see our previous statements for details on this issue).


Thanks to our friends at Blockchain.info, MtGox now has a workaround that will use a unique identifier created by Blockchain to show whether transactions have been modified or not. This will prevent any fraudulent use of the malleability issue and protect the assets of our customers.


Resuming Withdrawals


With this new system in place, MtGox should be able to resume withdrawals soon. At the beginning we will do so at a moderated pace and with new daily/monthly limits in place to prevent any problems with the new system and to take into account current market conditions.


In order to launch the new system, we are going through the following steps:


- Re-indexing the entire Blockchain (approx. 32 million entries).

- Fully deploying the new NTX ID.

- Implementing a new bitcoin withdrawal queue that needs to be tested.


We will update everyone again by Thursday at the latest.


Additionally, you may have noticed that we have added a new login system that sends you an email when you successfully access your account. This is an additional security layer, but as always we strongly encourage our customers to use the 2-step authorization options available in our Security Center.

Thank you again for your support, and we look forward to resume bitcoin withdrawals as quickly as possible.


Best regards,


MtGox Team

Mike Feb 17 Announcements / Announcements

Tokyo, Japan, February 15th, 2014

 

Dear MtGox Customers,

In order to implement our solution to the "transaction malleability" issue being faced by bitcoin exchanges and businesses, we are going to have a 6-hour downtime on all bitcoin deposits and internal bitcoin transfers in addition to the current pause on bitcoin withdrawals. Trading will otherwise still be open as usual.

Maintenance Schedule (approximate): 6pm ~ 12am JST (February 15th)

The above downtime period is approximate: it may be shortened or lengthened as required. Once the implementation is complete customers will again be able to deposit bitcoin, but we will be doing extensive testing before bitcoin withdrawals are reactivated. We will publish an update on the situation on Monday .

BlockChain.info have implemented changes to address the malleability issue. Our solution should work in the short term, while a longer-term solution is being discussed with the Bitcoin Core Dev team and the Bitcoin Foundation. We are also discussing this with other exchanges and businesses.

Thank you for your support during the maintenance, and we will update you on the progress shortly.

Best regards,

MtGox Team

Marion Feb 10 Announcements / Announcements

Dear MtGox Customers and Bitcoiners,

As you are aware, the MtGox team has been working hard to address an issue with the way that bitcoin withdrawals are processed. By "bitcoin withdrawal" we are referring to transactions from a MtGox bitcoin wallet to an external bitcoin address. Bitcoin transactions to any MtGox bitcoin address, and currency withdrawals (Yen, Euro, etc) are not affected by this issue.

The problem we have identified is not limited to MtGox, and affects all transactions where Bitcoins are being sent to a third party. We believe that the changes required for addressing this issue will be positive over the long term for the whole community. As a result we took the necessary action of suspending bitcoin withdrawals until this technical issue has been resolved.


Addressing Transaction Malleability
MtGox has detected unusual activity on its Bitcoin wallets and performed investigations during the past weeks. This confirmed the presence of transactions which need to be examined more closely. 


Non-technical Explanation: 
A bug in the bitcoin software makes it possible for someone to use the Bitcoin network to alter transaction details to make it seem like a sending of bitcoins to a bitcoin wallet did not occur when in fact it did occur. Since the transaction appears as if it has not proceeded correctly, the bitcoins may be resent. MtGox is working with the Bitcoin core development team and others to mitigate this issue.


Technical Explanation:
Bitcoin transactions are subject to a design issue that has been largely ignored, while known to at least a part of the Bitcoin core developers and mentioned on the BitcoinTalk forums. This defect, known as "transaction malleability" makes it possible for a third party to alter the hash of any freshly issued transaction without invalidating the signature, hence resulting in a similar transaction under a different hash. Of course only one of the two transactions can be validated. However, if the party who altered the transaction is fast enough, for example with a direct connection to different mining pools, or has even a small amount of mining power, it can easily cause the transaction hash alteration to be committed to the blockchain.

The bitcoin api "sendtoaddress" broadly used to send bitcoins to a given bitcoin address will return a transaction hash as a way to track the transaction's insertion in the blockchain.
Most wallet and exchange services will keep a record of this said hash in order to be able to respond to users should they inquire about their transaction. It is likely that these services will assume the transaction was not sent if it doesn't appear in the blockchain with the original hash and have currently no means to recognize the alternative transactions as theirs in an efficient way.

This means that an individual could request bitcoins from an exchange or wallet service, alter the resulting transaction's hash before inclusion in the blockchain, then contact the issuing service while claiming the transaction did not proceed. If the alteration fails, the user can simply send the bitcoins back and try again until successful.

We believe this can be addressed by using a different hash for transaction tracking purposes. While the network will continue to use the current hash for the purpose of inclusion in each block's Merkle Tree, the new hash's purpose will be to track a given transaction and can be computed and indexed by hashing the exact signed string via SHA256 (in the same way transactions are currently hashed).

This new transaction hash will allow signing parties to keep track of any transaction they have signed and can easily be computed, even for past transactions.

We have discussed this solution with the Bitcoin core developers and will allow Bitcoin withdrawals again once it has been approved and standardized. 

In the meantime, exchanges and wallet services - and any service sending coins directly to third parties - should be extremely careful with anyone claiming their transaction did not go through.

Note that this will also affect any other crypto-currency using the same transaction scheme as Bitcoin.


Conclusion
To put things in perspective, it's important to remember that Bitcoin is a very new technology and still very much in its early stages. What MtGox and the Bitcoin community have experienced in the past year has been an incredible and exciting challenge, and there is still much to do to further improve. 

MtGox will resume bitcoin withdrawals to outside wallets once the issue outlined above has been properly addressed in a manner that will best serve our customers.

More information on the status of this issue will be released as soon as possible. 

We thank you for taking the time to read this, and especially for your patience. 

Best Regards,
MtGox Team