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.
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 :ref:`Simple Payment Verification <spv>`
The seed is a random phrase that is used to generate your private keys.
Example:
constant forest adore false green weave stop guy fur freeze giggle clock
Your wallet can be entirely recovered from its seed. For this, select the "restore wallet" option in the startup.
The seed phrase created by Electrum has 132 bits of entropy. This means that it provides the same level of security as a Bitcoin private key (of length 256 bits). Indeed, an elliptic curve key of length n provides n/2 bits of security.
It is not possible to recover your password. However, you can restore restore your wallet from its seed phrase, and and choose a new password. If you lose both your password and your seed, there is no way to recover your money. This is why we ask you to save your seed phrase on paper.
Bitcoin transactions become 'confirmed' when miners accept to write them in the Bitcoin blockchain. In general, the speed of confirmation depends on the fee you attach to your transaction; miners prioritize transaction that pay the highest fees.
Recent versions of Electrum use 'dynamic fees', in order to make sure that the fee you pay with your transaction is adequate. This feature is enabled by default in recent versions of Electrum.
If you have made a transaction that is unconfirmed, you can:
- Wait for a long time. Eventually, your transaction will either be confirmed or cancelled. This might take several days.
- Increase the transaction fee. This is only possible for 'replaceable' transactions. To create this type of transaction, you must have enabled 'Replace by Fee' in your preferences, before sending the transaction.
- Create a 'Child Pays For Parent' transaction. A CPFP is a new transaction, that pays a high fee in order to compensate for the small fee of its parent transaction. It can be done by the recipient of the funds, or by the sender, if the transaction has a change output.
When you freeze an address, the funds in that address will not be used for sending bitcoins. You can not send Bitcoins if you don't have enough funds in the non-frozen addresses.
Electrum uses two separate levels of encryption:
- Your seed and private keys are encrypted using AES-256-CBC. The private keys are decrypted only briefly, when you need to sign a transaction; for this you need to enter your password. This is done in order to minimize the amount of time during which sensitive information is unencrypted in your computer's memory.
- In addition, your wallet file may be encrypted on disk. Note that the wallet information will remain unencrypted in the memory of your computer for the duration of your session. If a wallet is encrypted, then its password will be required in order to open it. Note that the password will not be kept in memory; Electrum does not need it in order to save the wallet on disk, because it uses asymmetric encryption (ECIES).
Wallet file encryption is activated by default since version 2.8. It is intended to protect your privacy, but also to prevent you from requesting bitcoins on a wallet that you do not control.
Yes. see :ref:`Cold Storage <coldstorage>`
In Electrum 2.0, you cannot import private keys in a wallet that has a seed. You should sweep them instead.
If you want to import private keys and not sweep them you need to create a special wallet that does not have a seed. For this, create a new wallet, select "restore", and instead of typing your seed, type a list of private keys, or a list of addresses if you want to create a watching-only wallet.
You will need to back up this wallet, because it cannot be recovered from seed.
Sweeping private keys means to send all the bitcoins they control to an existing address in your wallet. The private keys you sweep do not become a part of your wallet. Instead, all the bitcoins they control are sent to an address that has been deterministically generated from your wallet seed.
To sweep private keys go to Wallet menu -> Private Keys -> Sweep. Enter the private keys in the appropriate field. Leave the 'Address' field unchanged. That is the destination address and it'll be from your existing electrum wallet.
The default wallet file is called default_wallet which is created when you first run the application and located under the /wallets folder.
On Windows:
- Show hidden files
- Go to UsersYourUserNameAppDataRoamingElectrumwallets
On Mac:
- Open Finder
- Go to folder (shift+cmd+G) and type ~/.electrum
On Linux:
- Home Folder
- Go -> Location and type ~/.electrum
You can create a transaction with several outputs. In the GUI, type each address and amount on a line, separated by a comma.
Amounts are in the current unit set in the client. The total is shown in the GUI.
You can also import a CSV file in the 'Pay to' field, by clicking on the folder icon.
Electrum lets you create and sign raw transactions right from the user interface using a form.
This might happen if you are trying to spend a large number of transactions outputs (for example, if you have collected hundreds of donations from a Bitcoin faucet). When you send Bitcoins, Electrum looks for unspent coins that are in your wallet, in order to create a new transaction. Unspent coins can have different values, much like physical coins and bills.
If this happens, you should consolidate your transaction inputs, by sending smaller amounts of bitcoins to one of your wallet addresses; this would be the equivalent of exchanging a stack of nickels for a dollar bill.
The gap limit is the maximum number of consecutive unused addresses in your deterministic sequence of addresses. Electrum uses it in order to stop looking for addresses. In Electrum 2.0, it is set to 20 by default, so the client will get all addresses until 20 unused addresses are found.
Electrum will generate new addresses as you use them, until it hits the gap limit
If you need to pre-generate more addresses, you can do so by typing wallet.create_new_address(False) in the console. This command will generate one new address. Note that the address will be shown with a red background in the address tab, to indicate that it is beyond the gap limit. The red color will remain until the gap is filled.
WARNING: Addresses beyond the gap limit will not automatically be recovered from seed. To recover them will require either increasing the client's gap limit or generating new addresses until the used addresses are found.
If you wish to generate more than one address, you may use a 'for' loop. For example, if you wanted to generate 50 addresses, you could do this:
for x in range(0, 50):
print wallet.create_new_address(False)Warning: always save your wallet seed on paper before doing an upgrade.
To upgrade Electrum, just install the most recent version. The way to do this will depend on your OS.
Note that your wallet files are stored separately from the software, so you can safely remove the old version of the software if your OS does not do it for you.
Some Electrum upgrades will modify the format of your wallet files.
For this reason, it is not recommended to downgrade Electrum to an older version, once you have opened your wallet file with the new version. The older version will not always be able to read the new wallet file.
The following issues should be considered when upgrading Electrum 1.x wallets to Electrum 2.x:
- Electrum 2.x will need to regenerate all of your addresses during the upgrade process. Please allow it time to complete, and expect it to take a little longer than usual for Electrum to be ready.
- The contents of your wallet file will be replaced with an Electrum 2 wallet. This means Electrum 1.x will no longer be able to use your wallet once the upgrade is complete.
- The 'Addresses' tab will not show any addresses the first time you launch Electrum 2. This is expected behaviour. Restart Electrum 2 after the upgrade is complete and your addresses will be available.
- Offline copies of Electrum will not show the addresses at all because it cannot synchronize with the network. You can force an offline generation of a few addresses by typing the following into the Console: wallet.synchronize(). When it's complete, restart Electrum and your addresses will once again be available.