Electrum, Bitcoin's popular lightweight wallet, launched a new version of its software this week. Apart from a desktop client, Electrum 2.6 is now available on Android as well, with an iOS version soon to come.
At its heart, the mobile version of Electrum is no different from the available desktop version. The two are fully compatible as well; if the seed from one wallet is imported onto the other, all funds and transactions are synchronized. As such, users don't need to maintain two different balances on their desktop and mobile devices.
“The main difference between existing Electrum wallets and the mobile version is the user interface,” Electrum developer Thomas Voegtlin explained. “The look and feel is very different of course, I basically had to redesign that part from scratch. Compared to the desktop version, the mobile wallet is generally easier to use, and built around payment requests in particular – both incoming and outgoing. I've also added some extra tricks, like the option to use a second phone to create a completely safe cold storage device to sign transactions. And users will be able to buy and sell Bitcoin directly from the app later this year.”
Electrum offers a unique hybrid security model, that combines indexing the blockchain with Simple Payment Verification (SPV). The wallet retrieves its transaction history and balance from a single Electrum server, while it connects to a number of additional servers to fetch block headers and verify that transactions reported by the first server are really included in the blockchain. Private keys are generated on the client side, and are always controlled by the user.
Voegtlin said he believes his wallet offers a much-needed move away from centralized solutions, benefiting decentralization and the Bitcoin ecosystem as a whole.
“Most mobile users currently rely on wallet applications that trust centralized servers, often hosted by companies,” Voegtlin explained. “That offers very little security. In the worst case, users do not have control over their private keys, and the companies providing these apps can block transactions or even confiscate funds. Either intentionally, for example in order to comply with regulations, or unintentionally: their server could be hacked by a malicious employee or otherwise compromised. In the best case, the user controls his private keys, but still trusts a server for his balance and status. This means that whoever compromises the server can poison a user's wallet with fake transactions, for example, by falsely making them believe they received Bitcoin. And of course, these wallets offer very little privacy.”
He added:
“Electrum is based on open source software, and users control their own money. The wallet is also faster than other SPV-wallets, which need to scan the blockchain, and offers more privacy since the list of wallet addresses are not sent over the Bitcoin network.”
While reliable user statistics are typically not easy to get in the open source and privacy aware Bitcoin space, it's safe to say that Electrum is one of the most used – if not the most used – software wallets available. Extrapolating data from his own Electrum server, Voegtlin estimates that some 10 percent of all transactions on the network are sent with the open-source software wallet.