From 7934ed8ef986ae2910f0e0a9e765e595bbbcac01 Mon Sep 17 00:00:00 2001 From: crocket <748856+crocket@users.noreply.github.com> Date: Tue, 30 Mar 2021 10:51:26 +0900 Subject: [PATCH] Document offline signing --- docs/interacting/offline-signing.md | 238 ++++++++++++++++++++++++++++ mkdocs.yml | 1 + 2 files changed, 239 insertions(+) create mode 100644 docs/interacting/offline-signing.md diff --git a/docs/interacting/offline-signing.md b/docs/interacting/offline-signing.md new file mode 100644 index 0000000..f32e4ae --- /dev/null +++ b/docs/interacting/offline-signing.md @@ -0,0 +1,238 @@ +# Offline Signing + +Offline signing involves + +* Creating an unsigned transaction on a view-only wallet +* Moving the unsigned transaction to an offline machine +* Signing the unsigned transaction on an offline wallet +* Moving the signed transaction to a view-only wallet +* Broadcasting the transaction + +It is securer than a hardware wallet connected to an online computer via a USB +cable. It is also more versatile than a hardware wallet. + +## Creating a new offline wallet + +Constructing a new offline wallet is done by executing + +``` +monero-wallet-cli --generate-new-wallet /path/to/wallet-file +``` + +on an offline machine. Record the seed on paper by executing `seed` on the +offline wallet. + +## Creating a new offline wallet with seed offset passphrase + +Seed and seed offset passphrase combine to create a new seed. You can store seed +and seed offset passphrase in separate places so that a thief can't steal your +fund without stealing seed and seed offset passphrase. I recommend 6 to 8 +(english) words as a seed offset passphrase as one english word has 11 bits of +entropy on average and 8 words have 88 bits of entropy. With seed passphrase, +you can also create decoy wallets that contain a little bit of money and can +protect you from torturers or blackmailers who demand money from you. + +If you want to create an offline wallet with seed and seed passphrase, +create an offline wallet, record the seed on paper, delete the wallet file, +generate seed offset passphrase, record seed offset passphrase on paper, and +execute + +``` +monero-wallet-cli --generate-new-wallet /path/to/wallet-file \ +---restore-deterministic-wallet +``` + +to restore from seed and seed offset passphrase. When you restore from seed, you +can enter seed offset passphrase. + +Generate seed offset passphrase on an offline machine or with diceware because +humans are bad at creating random passphrases. + +If you want to reconstruct an existing offline wallet that received or sent +transactions, you need extra steps. Refer to `Restoring offline wallet`. + +## Creating a new view-only wallet + +To create a view-only wallet, copy primary address and secret view key from an +offline wallet to an online machine where a view-only wallet is going to be +created. You can get primary address by executing `address` on an offline wallet +and secret view key by executing `viewkey` on the offline wallet. + +You can use a microSD card and two USB microSD card readers to exchange data +between an offline wallet and a view-only wallet. You can also use a USB flash +drive. + +To create a view-only wallet on an online machine, execute + +``` +monero-wallet-cli --generate-from-view-key /path/to/wallet-file \ +--daemon-address remote-node-address:port +``` + +If you want to reconstruct an existing view-only wallet that received or sent +transactions, refer to `Restoring view-only wallet`. + +## Launching offline wallet + +Execute + +``` +monero-wallet-cli --wallet-file /path/to/wallet-file +``` + +## Launching a view-only wallet + +Execute + +``` +monero-wallet-cli --wallet-file /path/to/wallet-file \ +--daemon-address remote-node-address:port +``` + +It's safe to sync your wallet over clearnet. If you want to broadcast a +transaction without revealing your IP address, execute + +``` +monero-wallet-cli --wallet-file /path/to/wallet-file \ +--daemon-address tor-or-i2p-remote-node-address:port \ +--proxy 127.0.0.1:tor-or-i2p-port +``` + +Synchronizing wallet over clearnet is a lot faster than doing it on tor or i2p. +Thus, consider synchronizing over clearnet even if you broadcast transactions +over tor or i2p. + +## Offline transaction signing + +Execute any wallet command that transfers monero to any address. For example, + +``` +transfer xmr-address amount-of-xmr-to-send +``` + +Any transfer command on a view-only wallet creates `unsigned_monero_tx` in the +current working directory. + +Move `unsigned_monero_tx` to an offline machine that has an offline wallet. +Execute + +``` +sign_transfer +``` + +on the offline wallet in the directory with `unsigned_monero_tx`. +`signed_monero_tx` file is created in the current working directory. Move +`signed_monero_tx` to the online machine with a view-only wallet. In the +directory with `signed_monero_tx`, launch the view-only wallet, and execute + +``` +submit_transfer +``` + +Because a view-only wallet doesn't have key images, it can't see outgoing +transactions. To make a view-only wallet see outgoing transactions, it has +to export new outputs created by `submit_transfer` to an offline wallet which +creates key images out of new outputs. + +Execute + +``` +export_outputs outputs +``` + +on a view-only wallet. Move `outputs` file to the offline machine with an offline +wallet. Launch the offline wallet, and execute + +``` +import_outputs /path/to/outputs +``` + +Export key images derived from new outputs by executing + +``` +export_key_images key_images +``` + +on an offline wallet. Move `key_images` file to the machine with a view-only +wallet. Launch the view-only wallet, and execute + +``` +import_key_images /path/to/key_images +``` + +## Updating wallet softwares on an offline signing machine + +When you update an offline machine with offline wallets, you can't just +connect the machine to the internet and update wallet softwares because +doing so exposes offline wallets to the internet. + +Instead, boot OS installation media, wipe filesystems, and then connect +to the internet, and install everything from scratch again. + +If your root filesystem is encrypted, OS installation media can connect +to the internet from the beginning because encrypted data are safe until +they are decrypted. + +## Restoring offline wallet + +After updating wallet softwares on an offline signing machine by wiping it out +and reinstalling everything, you have to restore offline wallet. + +Restore an offline wallet from seed (and seed offset passphrase) by executing + +``` +monero-wallet-cli --generate-new-wallet wallet-file --restore-deterministic-wallet +``` + +The new offline wallet can't sign new transactions because it doesn't have +all trasaction outputs that precede a new unsigned transaction. Thus, it first +has to import all outputs from a view-only wallet. + +On a view-only wallet that was derived from the offline wallet, execute + +``` +export_outputs all all_outputs +``` + +`all` is important because `export_outputs` exports only new outputs that weren't +exported before, but + +``` +export_outputs all +``` + +exports all outputs. Move `all_outputs` file to the offline machine with the +offline wallet. Execute + +``` +import_outputs /path/to/all_outputs +``` + +on the new offline wallet. + +## Restoring view-only wallet + +If you reconstruct view-only wallet, because it doesn't have key images, +it can't see outgoing transactions. If it can't see outgoing transactions, +it reports wrong account balances. Thus, it has to import all key images +from its corresponding offline wallet. + +On the offline wallet, execute + +``` +export_key_images all all_key_images +``` + +`export_key_images` doesn't work because it exports only new key images that +weren't exported before. + +``` +export_key_images all +``` + +exports all key images. Move `all_key_images` file to the machine with the +view-only wallet. Execute + +``` +import_key_images /path/to/all_key_images +``` diff --git a/mkdocs.yml b/mkdocs.yml index 762862e..7c79fbc 100644 --- a/mkdocs.yml +++ b/mkdocs.yml @@ -14,6 +14,7 @@ nav: - Verify: 'interacting/verify-monero-binaries.md' - Overview: 'interacting/overview.md' - Config file: 'interacting/monero-config-file.md' + - Offline Signing: 'interacting/offline-signing.md' - monerod: 'interacting/monerod-reference.md' - monero-wallet-cli: 'interacting/monero-wallet-cli-reference.md' - monero-wallet-gui: 'interacting/monero-wallet-gui-reference.md'