Electrum Documentation Release 3.3 Thomas Voegtlin Sep 07, 2021 GUI and beginners 1 Frequently Asked Questions 3 1.1 How does Electrum work?........................................3 1.2 Does Electrum trust servers?.......................................3 1.3 What is the seed?.............................................4 1.4 How secure is the seed?.........................................4 1.5 I have forgotten my password. What can I do?.............................4 1.6 How does Electrum get the Bitcoin price it uses?............................4 1.7 My transaction has been unconfirmed for a long time. What can I do?.................4 1.8 What does it mean to “freeze” an address in Electrum?.........................5 1.9 How is the wallet encrypted?.......................................5 1.10 Does Electrum support cold wallets?..................................5 1.11 Can I import private keys from other Bitcoin clients?..........................5 1.12 Can I sweep private keys from other Bitcoin clients?..........................6 1.13 Where is the Electrum datadir located?.................................6 1.14 Where is my wallet file located?.....................................7 1.15 How to enable debug logging?......................................7 1.16 Can I do bulk payments with Electrum? (batching)...........................7 1.17 Can Electrum create and sign raw transactions?.............................8 1.18 Electrum freezes when I try to send bitcoins...............................8 1.19 What is the gap limit?..........................................8 1.20 How can I pre-generate new addresses?.................................9 1.21 How do I upgrade Electrum?.......................................9 1.22 My anti-virus has flagged Electrum as malware! What now?......................9 1.23 Electrum requires recent Python. My Linux distribution does not yet have it. What now?....... 10 1.24 I might run my own server. Are client-server connections authenticated?............... 10 1.25 Does Electrum support altcoins (“cryptocurrencies”)?......................... 11 2 Invoices 13 3 Two Factor Authentication 15 3.1 Creating a Wallet............................................. 16 3.2 Restoring from seed........................................... 17 4 Multisig Wallets 19 4.1 Create a pair of 2-of-2 wallets...................................... 19 4.2 Receiving................................................. 21 4.3 Spending................................................. 21 i 5 Cold Storage 25 5.1 Create an offline wallet.......................................... 25 5.2 Create a watching-only version of your wallet.............................. 26 5.3 Create an unsigned transaction...................................... 27 5.4 Get your transaction signed....................................... 28 5.5 Broadcast your transaction........................................ 30 6 Hardware wallets on Linux 31 6.1 1. Dependencies............................................. 31 6.2 2. Python libraries............................................ 31 6.3 3. udev rules............................................... 32 6.4 4. Done.................................................. 32 7 Using the most current Electrum on Tails 33 7.1 Steps to use AppImage.......................................... 33 8 Plugins 35 8.1 Audio Modem.............................................. 35 8.2 Cosigner Pool.............................................. 35 8.3 Email................................................... 35 8.4 LabelSync................................................ 35 8.5 Revealer................................................. 36 8.6 Two Factor Authentication........................................ 36 8.7 Virtual Keyboard............................................. 36 9 Using cold storage with the command line 37 9.1 Create an unsigned transaction...................................... 37 9.2 Sign the transaction........................................... 37 9.3 Broadcast the transaction......................................... 37 10 How to split your coins using Electrum in case of a fork 39 10.1 Note:................................................... 39 10.2 What is a fork?.............................................. 39 10.3 What does it mean to ‘split your coins’?................................. 39 10.4 Fork detection.............................................. 39 10.5 Procedure................................................. 40 11 Using Electrum Through Tor 45 11.1 List of Active .onion servers....................................... 45 11.2 LINUX.................................................. 45 11.3 Option 1: Single Server......................................... 45 11.4 Option 2: Multiple servers but Tor Main................................. 46 11.5 WINDOWS............................................... 46 11.6 Option 1: Connecting to a single Server................................. 46 11.7 Option 2................................................. 47 12 Verifying GPG signature of Electrum using Linux command line 49 12.1 Obtain public GPG key for ThomasV.................................. 49 12.2 Download Electrum and signature file (asc)............................... 49 12.3 Verify GPG signature.......................................... 49 13 Command Line 51 13.1 Using the inline help........................................... 51 13.2 How to use the daemon......................................... 51 13.3 Magic words............................................... 52 ii 13.4 Aliases.................................................. 52 13.5 Formatting outputs using jq....................................... 52 13.6 Examples................................................. 53 14 How to configure SSL with Electrum 55 14.1 Add your SSL private key........................................ 55 14.2 Add your SSL certificate bundle..................................... 55 14.3 Check that your certificate was accepted by Electrum.......................... 56 15 How to accept Bitcoin on a website using Electrum 57 15.1 Add your SSL certificate to Electrum.................................. 57 15.2 Create and use your merchant wallet................................... 57 15.3 Start the Electrum daemon........................................ 58 15.4 Create a signed payment request..................................... 58 15.5 Open the payment request page in your browser............................ 58 15.6 Lightning payments........................................... 60 16 How to setup a watchtower 63 16.1 How to configure a watchtower..................................... 63 16.2 Configure the watchtower in your client................................. 64 17 JSONRPC interface 65 18 The Python Console 67 19 Simple Payment Verification 69 20 Electrum Seed Version System 71 20.1 Description................................................ 71 20.2 Motivation................................................ 71 20.3 Version number.............................................. 72 20.4 List of reserved numbers......................................... 72 20.5 Seed generation............................................. 73 20.6 Security implications........................................... 73 21 Electrum protocol specification 75 21.1 Format.................................................. 75 21.2 Methods................................................. 76 21.3 External links............................................... 80 22 Serialization of unsigned or partially signed transactions 83 22.1 Extended public keys........................................... 83 22.2 Public key................................................ 83 22.3 BIP32 derivation............................................. 84 22.4 Legacy Electrum Derivation....................................... 84 22.5 Bitcoin address.............................................. 84 23 Plugin rules: 85 iii iv Electrum Documentation, Release 3.3 Electrum is a lightweight Bitcoin wallet. GUI and beginners 1 Electrum Documentation, Release 3.3 2 GUI and beginners CHAPTER 1 Frequently Asked Questions 1.1 How does Electrum work? Electrum’s focus is speed, with low resource usage and simplifying Bitcoin. Startup times are instant because it operates in conjunction with high-performance servers that handle the most complicated parts of the Bitcoin system. 1.2 Does Electrum trust servers? In short, not really. The Electrum client never sends private keys to the servers. In addition, it verifies the information reported by servers, using a technique called Simple Payment Verification By default, Electrum tries to maintain connections to ~10 servers. The client subscribes to block header notifications to all of these, and also periodically polls each for dynamic fee estimates. For all connected servers except one, that is all they are used for. Getting block headers from multiple sources is useful to detect lagging servers, chain splits and forks. One of the servers, arbitrarily, is selected as the “main” server. • The client subscribes to its own addresses (nit: sha256 hashes of scriptPubKeys) so that it would be notified of new transactions touching them. It also synchronizes the existing history of its addresses. This means the client sacrifices some privacy to the server, as the server can now reasonably guess that all these addresses belong to the same entity. • As above, confirmed transactions are verified via SPV. • The server is trusted about unconfirmed transactions. • The server can lie by omission. That is, it can