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Document offline signing
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docs/interacting/offline-signing.md
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docs/interacting/offline-signing.md
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# Offline Signing
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Offline signing involves
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* Creating an unsigned transaction on a view-only wallet
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* Moving the unsigned transaction to an offline machine
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* Signing the unsigned transaction on an offline wallet
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* Moving the signed transaction to a view-only wallet
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* Broadcasting the transaction
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It is securer than a hardware wallet connected to an online computer via a USB
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cable. It is also more versatile than a hardware wallet.
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## Creating a new offline wallet
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Constructing a new offline wallet is done by executing
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```
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monero-wallet-cli --generate-new-wallet /path/to/wallet-file
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```
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on an offline machine. Record the seed on paper by executing `seed` on the
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offline wallet.
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## Creating a new offline wallet with seed offset passphrase
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Seed and seed offset passphrase combine to create a new seed. You can store seed
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and seed offset passphrase in separate places so that a thief can't steal your
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fund without stealing seed and seed offset passphrase. I recommend 6 to 8
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(english) words as a seed offset passphrase as one english word has 11 bits of
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entropy on average and 8 words have 88 bits of entropy. With seed passphrase,
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you can also create decoy wallets that contain a little bit of money and can
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protect you from torturers or blackmailers who demand money from you.
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If you want to create an offline wallet with seed and seed passphrase,
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create an offline wallet, record the seed on paper, delete the wallet file,
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generate seed offset passphrase, record seed offset passphrase on paper, and
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execute
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```
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monero-wallet-cli --generate-new-wallet /path/to/wallet-file \
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---restore-deterministic-wallet
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```
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to restore from seed and seed offset passphrase. When you restore from seed, you
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can enter seed offset passphrase.
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Generate seed offset passphrase on an offline machine or with diceware because
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humans are bad at creating random passphrases.
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If you want to reconstruct an existing offline wallet that received or sent
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transactions, you need extra steps. Refer to `Restoring offline wallet`.
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## Creating a new view-only wallet
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To create a view-only wallet, copy primary address and secret view key from an
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offline wallet to an online machine where a view-only wallet is going to be
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created. You can get primary address by executing `address` on an offline wallet
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and secret view key by executing `viewkey` on the offline wallet.
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You can use a microSD card and two USB microSD card readers to exchange data
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between an offline wallet and a view-only wallet. You can also use a USB flash
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drive.
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To create a view-only wallet on an online machine, execute
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```
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monero-wallet-cli --generate-from-view-key /path/to/wallet-file \
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--daemon-address remote-node-address:port
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```
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If you want to reconstruct an existing view-only wallet that received or sent
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transactions, refer to `Restoring view-only wallet`.
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## Launching offline wallet
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Execute
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```
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monero-wallet-cli --wallet-file /path/to/wallet-file
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```
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## Launching a view-only wallet
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Execute
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```
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monero-wallet-cli --wallet-file /path/to/wallet-file \
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--daemon-address remote-node-address:port
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```
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It's safe to sync your wallet over clearnet. If you want to broadcast a
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transaction without revealing your IP address, execute
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```
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monero-wallet-cli --wallet-file /path/to/wallet-file \
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--daemon-address tor-or-i2p-remote-node-address:port \
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--proxy 127.0.0.1:tor-or-i2p-port
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```
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Synchronizing wallet over clearnet is a lot faster than doing it on tor or i2p.
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Thus, consider synchronizing over clearnet even if you broadcast transactions
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over tor or i2p.
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## Offline transaction signing
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Execute any wallet command that transfers monero to any address. For example,
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```
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transfer xmr-address amount-of-xmr-to-send
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```
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Any transfer command on a view-only wallet creates `unsigned_monero_tx` in the
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current working directory.
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Move `unsigned_monero_tx` to an offline machine that has an offline wallet.
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Execute
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```
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sign_transfer
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```
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on the offline wallet in the directory with `unsigned_monero_tx`.
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`signed_monero_tx` file is created in the current working directory. Move
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`signed_monero_tx` to the online machine with a view-only wallet. In the
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directory with `signed_monero_tx`, launch the view-only wallet, and execute
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```
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submit_transfer
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```
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Because a view-only wallet doesn't have key images, it can't see outgoing
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transactions. To make a view-only wallet see outgoing transactions, it has
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to export new outputs created by `submit_transfer` to an offline wallet which
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creates key images out of new outputs.
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Execute
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```
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export_outputs outputs
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```
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on a view-only wallet. Move `outputs` file to the offline machine with an offline
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wallet. Launch the offline wallet, and execute
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```
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import_outputs /path/to/outputs
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```
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Export key images derived from new outputs by executing
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```
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export_key_images key_images
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```
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on an offline wallet. Move `key_images` file to the machine with a view-only
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wallet. Launch the view-only wallet, and execute
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```
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import_key_images /path/to/key_images
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```
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## Updating wallet softwares on an offline signing machine
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When you update an offline machine with offline wallets, you can't just
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connect the machine to the internet and update wallet softwares because
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doing so exposes offline wallets to the internet.
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Instead, boot OS installation media, wipe filesystems, and then connect
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to the internet, and install everything from scratch again.
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If your root filesystem is encrypted, OS installation media can connect
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to the internet from the beginning because encrypted data are safe until
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they are decrypted.
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## Restoring offline wallet
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After updating wallet softwares on an offline signing machine by wiping it out
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and reinstalling everything, you have to restore offline wallet.
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Restore an offline wallet from seed (and seed offset passphrase) by executing
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```
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monero-wallet-cli --generate-new-wallet wallet-file --restore-deterministic-wallet
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```
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The new offline wallet can't sign new transactions because it doesn't have
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all trasaction outputs that precede a new unsigned transaction. Thus, it first
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has to import all outputs from a view-only wallet.
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On a view-only wallet that was derived from the offline wallet, execute
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```
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export_outputs all all_outputs
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```
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`all` is important because `export_outputs` exports only new outputs that weren't
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exported before, but
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```
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export_outputs all
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```
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exports all outputs. Move `all_outputs` file to the offline machine with the
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offline wallet. Execute
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```
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import_outputs /path/to/all_outputs
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```
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on the new offline wallet.
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## Restoring view-only wallet
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If you reconstruct view-only wallet, because it doesn't have key images,
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it can't see outgoing transactions. If it can't see outgoing transactions,
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it reports wrong account balances. Thus, it has to import all key images
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from its corresponding offline wallet.
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On the offline wallet, execute
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```
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export_key_images all all_key_images
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```
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`export_key_images` doesn't work because it exports only new key images that
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weren't exported before.
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```
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export_key_images all
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```
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exports all key images. Move `all_key_images` file to the machine with the
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view-only wallet. Execute
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```
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import_key_images /path/to/all_key_images
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```
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@ -14,6 +14,7 @@ nav:
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- Verify: 'interacting/verify-monero-binaries.md'
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- Overview: 'interacting/overview.md'
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- Config file: 'interacting/monero-config-file.md'
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- Offline Signing: 'interacting/offline-signing.md'
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- monerod: 'interacting/monerod-reference.md'
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- monero-wallet-cli: 'interacting/monero-wallet-cli-reference.md'
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- monero-wallet-gui: 'interacting/monero-wallet-gui-reference.md'
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