This past weekend and week saw a spike in the number of invalid blocks being mined by Bitcoin miners and a few forks of the Bitcoin blockchain started as result. To avoid this, the Bitcoin Core developers have alerted everyone who is running on software older than 0.9.5 to upgrade to 0.10.2. See below for more information and resources.

Also in the world this week, China and Greece have been continuing to suffer economic downturns. For Greece this has led to a media row in how the Greeks could turn to Bitcoin to avoid economic woes, however, it doesn’t seem like the Greek people know much about bitcoin at all (nor are they entirely favored to buy in.) However, hoping to capitalize on the potential for Greeks looking for bitcoins, Polish Bitcoin exchange Bitcurex has started a fee-free service for Greek customers.

While you’re here also take a look at MIT’s Enigma Project, an interesting idea that would use the blockchain to allow for computational privacy on data–thus permitting multiple parties to analyze data without fully revealing the underlying data itself to any one party. And also check out ArcBit, a privacy-focused iOS wallet produced by an ex-Blockchain.info developer.

Finally, there’s some music at the end of the Weekly in the form of a YouTube video, so be sure to read all the way through.

Update to Bitcoin Core 0.10.2 to avoid invalid blocks problem

Recently the Bitcoin Core developers released an alert that issues have become apparent with older versions of the Bitcoin Core and certain miners have been producing invalid blocks. To avoid this problem it is suggested that anyone using a Bitcoin wallet or mining software update to Bitcoin Core 0.10.2.

People using Bitcoin Core 0.9.5 or later are unaffected; but it is still recommended to upgrade to the latest version to receive all recent security fixes.

If you are still running an older version, allow for at an additional 30 confirmations before assuming a transaction is safe.

In summary, what happened is some miners are currently producing invalid blocks. Older software running on the Bitcoin network can accept these invalid blocks under certain conditions. So far there have been two forks that happened due to invalid blocks: one on July 4, resulting in 6 blocks; and one in July 5, resulting in 3 blocks. There is no evidence of double-spends occurring during either of these forks.

This issue is ongoing is not yet resolved. If you are still running on 0.9.5 you must continue to wait an additional 30 confirmations and it is highly recommended you upgrade.

The Enigma Project at MIT

MIT’s Enigma Project: Decentralized computation privacy using the Bitcoin blockchain

MIT has long been on the forefront of computer technology and has been in the news taking an interest in Bitcoin and the Bitcoin blockchain protocol. Now that interest is bearing fruit with the Enigma Project, a privacy-centric cloud platform that uses the Bitcoin blockchain to enable storing encrypted data and compute with it without needing to fully reveal the data to any party involved.

Created by Guy Zyskind and Oz Nathan, Enigma is aided by cryptographer Ranjit Kumaresan and advised by Professor Alex Pentland, computer scientist and Toshiba professor at MIT. Prof. Pentland is also known for helping create the Media Lab at MIT, which is the umbrella laboratory harboring the Enigma Project.

Technical details for the project are available in a whitepaper [PDF] that outlines how peer-to-peer networking in the blockchain can be used to provide computational capability while securing privacy:

A peer-to-peer network, enabling different parties to jointly store and run computations on data while keeping the data completely private. Enigma’s computational model is based on a highly optimized version of secure multi-party computation, guaranteed by a verifiable secret-sharing scheme. For storage, we use a modified distributed hashtable for holding secret-shared data. An external blockchain is utilized as the controller of the network, manages access control, identities and serves as a tamper-proof log of events. Security deposits and fees incentivize operation, correctness and fairness of the system. Similar to Bitcoin, Enigma removes the need for a trusted third party, enabling autonomous control of personal data. For the first time, users are able to share their data with cryptographic guarantees regarding their privacy.

The idea is ambitious, but interesting, and has a lot of possible implications for the data market. The project is also preparing to launch into beta and signups are available on the website.

Former Blockchain.info developer launches ArcBit, a competing Bitcoin wallet

Due to privacy practices he disagrees with over at Blockchain.info, Timothy Lee, a former software developer at said Bitcoin web wallet service, launched his own Bitcoin wallet dubbed ArcBit. He spoke with CoinTelegraph about the launch and his expectations for this wallet and consumers.

“At Blockchain.info, I was the primary person working on the HD wallet for the iOS and Web wallet…” Lee said. “While I was there, the company was making some design decisions on the wallet that I wish weren’t made. One of those decisions ended up costing users some privacy, something I disagreed with.”

This became the impetus for creating ArcBit, a wallet that stores all private keys on the users’ device and they are not shared with ArcBit’s servers.

Currently ArcBit only has an iOS version, but it supports a feature not seen in other wallets: stealth addresses. Lee claims this will make ArcBit the only iOS Bitcoin wallet that supports stealth addresses on the market.

Stealth addresses were first announced in 2014 and outlined in a paper authored by Peter Todd based on input from Gregory Maxwell, Adam Back and Amir Taaki. The paper proposes a type of bitcoin address that allows payees to use a single, fixed address that payers can send funds to without revealing underlying transactions.

Other ArcBit features include:

• Single recovery passphrase that works forever;
• Optional PIN protection;
• Open source: https://github.com/arcbit/arcbit-ios;
• Advance mode for bitcoin experts;
• Import private keys support;
• Import BIP38 encrypted private keys support;
• Import watch only addresses support;
• Import HD wallet account keys support;
• Import HD wallet watch only account keys support.

Currently available for iOS, the ArcBit wallet is free to use.

Bitcurex launches no-fees service for Greece

Greece has been facing dire financial troubles recently involving European loans to bolster the country’s guttering economy. Recently, 61 per cent of Greek voters voted against budget cuts proposed by creditors for rescue loans. As the economy of Greece continues to suffer, many Bitcoin luminaries and fans have suggested that Greek citizens may turn to bitcoin.

To take advantage of a potential rally from Greece to BTC, Poland-based Bitcoin exchange Bitcurex has launched a zero-fee service for Greek citizens:

We are happy to inform you about our new promo: if you are a Greek citizen, all you have to do is sign up at Bitcurex and verify your account – then you get zero fees for a 3 month period.

More info about Greek crisis at satoshi.pl

Best Regards,

Bitcurex Team

Although Bitcurex is barely visible in the Bitcoin media world, the exchange has been around since 2012. It is also claimed to be one of the more popular European exchanges. With this outreach to Greek citizens, Bitcurex is hoping to make themselves a name and find more popularity in the European market.

Music: Welcome to the Blockchain

Toby Granger on YouTube released the above song some months ago. We’re including this in the Bitcoin Weekly because it’s a perfect example of how culture and technology collide in the Bitcoin community.

Support the artist! Lyrics and raps by Toby Ganger (there’s a bitcoin donation address on his site), produced by Decap, and additional vocals by Jimetta Rose. The music is recorded at Manifest Studios, Santa Monica, CA.