Ckb-auth library is able to verify a lot of blockchain signatures including the monero.
We can use monero-wallet-cli (or other compatible wallet) to generate valid signatures and validate them on-chain with ckb-auth.
A simple way to use monero signature algorithm to lock ckb cells
is to sign the transaction hash (or maybe sighash_all, i.e. hashing all fields
including transaction hash and other witnesses in this input group)
with monero-wallet-cli, and then leverage ckb-auth to check the validity of this signature.
See the docs for more details.
Assume that the message (sighash_all result) to be signed is
8fe9f62674d51f3103a3635433e73b4fcdadf6faa3b0c8392546ca6af161aa12
Here the argument given to -a is the address of monero account, while the argument given to -m refers to
whether the spend key or view key is used to sign the transaction (only spend key mode is supported).
ckb-auth-cli monero parse -a 41eBLjYsK28CJD5z2b7FojMCDg6vERASShVZqAvnsC9LhS7saG8CmMo5Rm92wgnT8wa6nJVu57MHHjmnoyvTpCG7NQ7dErc -m spend
which outputs
a55ec8bb5b93aaffefd754996cb097228839aad6
Following the steps below to set up a monero wallet, save above message to a binary file,
e.g. running printf "$(printf 157ea09579f09cf96307f6b23d6fd61c3cff123076d44c27e2e9bedf02135e87 | fold -w 2 | xargs -n 1 printf '\\x%s')" > ckb-auth-test-message
to save it to ckb-auth-test-message. To sign this message, finally run
monero-wallet-cli --wallet-file ckb-auth-test-wallet --password pw sign ckb-auth-test-message
which outputs
SigV23ZKheximq145tW14dshL17Jpqp2GJn296GfRnGqt3pMeaZU7xoEEAFr2Xm7Jc7xZjYWf6KhstZanA73to7uF6rea
Stripping prefix SigV2, this is the base64-encoded signature.
ckb-auth-cli monero verify -p a55ec8bb5b93aaffefd754996cb097228839aad6 -s 3ZKheximq145tW14dshL17Jpqp2GJn296GfRnGqt3pMeaZU7xoEEAFr2Xm7Jc7xZjYWf6KhstZanA73to7uF6rea -a 41eBLjYsK28CJD5z2b7FojMCDg6vERASShVZqAvnsC9LhS7saG8CmMo5Rm92wgnT8wa6nJVu57MHHjmnoyvTpCG7NQ7dErc --mode spend --message 157ea09579f09cf96307f6b23d6fd61c3cff123076d44c27e2e9bedf02135e87
This commands return zero if and only if verification succeeded.
The commands below download the official monero binaries (e.g. monerod for monero daemon,
monero-wallet-cli for monero command line client) into the directory /usr/local.
tarball=monero-wallet-cli.tar.gz
wget -O "$tarball" https://downloads.getmonero.org/cli/monero-linux-x64-v0.18.2.2.tar.bz2
tar xvaf "$tarball"
sudo cp -r monero-*/* /usr/local/
You will need to create a new wallet to sign transactions with monero-wallet-cli.
One option is to generate a all-new wallet by running
monero-wallet-cli --offline --generate-new-wallet ckb-auth-test-wallet
Just follow the instructions to create a new wallet.
To import an account with address 41eBLjYsK28CJD5z2b7FojMCDg6vERASShVZqAvnsC9LhS7saG8CmMo5Rm92wgnT8wa6nJVu57MHHjmnoyvTpCG7NQ7dErc into a wallet named ckb-auth-test-wallet non-interactively, we can first create a file which is to be used as the stdin of a following monero-wallet-cli.
cat <<EOF >commands
41eBLjYsK28CJD5z2b7FojMCDg6vERASShVZqAvnsC9LhS7saG8CmMo5Rm92wgnT8wa6nJVu57MHHjmnoyvTpCG7NQ7dErc
8ef26aced8b5f8e1e8ce63b6c75ac6ee41424242424242424242424242424202
972874ae95f5c167285858141e940847398f9c246c7913c0d396b6d73b484105
pw
pw
0
N
EOF
Here 8ef26aced8b5f8e1e8ce63b6c75ac6ee41424242424242424242424242424202 and 972874ae95f5c167285858141e940847398f9c246c7913c0d396b6d73b484105 are respectively the spend private key and view private key of this account.
We can then run the following command to import this account.
monero-wallet-cli --offline --generate-from-keys ckb-auth-test-wallet < commands
See also Creating a wallet in non-interactive mode using monero-wallet-cli? - Monero Stack Exchange.
Running monero-wallet-cli --wallet-file ckb-auth-test-wallet --password pw --offline to enter the interactive mode of
monero command line wallet.
[wallet 41eBLj (no daemon)]: viewkey
Wallet password:
secret: 972874ae95f5c167285858141e940847398f9c246c7913c0d396b6d73b484105
public: bbcb8c902571ae1a777f7f07a023ecc5e3d83ba624d4b0ffb7eff79e8b5d10bd
[wallet 41eBLj (no daemon)]: spendkey
Wallet password:
secret: 8ef26aced8b5f8e1e8ce63b6c75ac6ee41424242424242424242424242424202
public: 007caf7a553a894389dd562115b17e78ba84a5c7692677f216c54385dc5c6ff1
[wallet 41eBLj (no daemon)]: address
0 41eBLjYsK28CJD5z2b7FojMCDg6vERASShVZqAvnsC9LhS7saG8CmMo5Rm92wgnT8wa6nJVu57MHHjmnoyvTpCG7NQ7dErc Primary address
Currently, ckb-auth uses mode, spend public key, view public key to compute pubkey hash of monero account. To be more specific,
pubkey_hash = blake2b_256(mode || pub_spend_key || pub_view_key)
Here mode indicates whether we are using the spend key or the view key.
Although there are flags --spend and --view for monero-wallet-cli to toggle whether to
use spend key or view key to sign a message. We only support signing transactions with spend key.
Thus the only valid value for mode is 0, which
represents that we used spend key to sign the message.
For example if the account we are using to sign messages is as above, i.e. it has
public spend key 007caf7a553a894389dd562115b17e78ba84a5c7692677f216c54385dc5c6ff1 and
public view key bbcb8c902571ae1a777f7f07a023ecc5e3d83ba624d4b0ffb7eff79e8b5d10bd.
Then the pubkey hash a55ec8bb5b93aaffefd754996cb097228839aad6 is just the blake2b 256 hash of 00007caf7a553a894389dd562115b17e78ba84a5c7692677f216c54385dc5c6ff1bbcb8c902571ae1a777f7f07a023ecc5e3d83ba624d4b0ffb7eff79e8b5d10bd.
In order for monero-wallet-cli to sign a message, we need first create a message file.
Normally the message the binary representation of a hash, we can create such binary file easily with
printf '%b' $(printf 4242424242424242424242424242424242424242424242424242424242424242 | fold -b2 | sed 's#^#\\x#') > message
Here message is a binary file with 32 repeated bytes of 0x42. Change the command to suit your needs.
We can sign a message with spend key by running
monero-wallet-cli --wallet-file ckb-auth-test-wallet --password pw sign message
Below is a sample output of the above command.
This is the command line monero wallet. It needs to connect to a monero
daemon to work correctly.
WARNING: Do not reuse your Monero keys on another fork, UNLESS this fork has key reuse mitigations built in. Doing so will harm your privacy.
Monero 'Fluorine Fermi' (v0.18.1.2-unknown)
Logging to monero-wallet-cli.log
Opened wallet: 41eBLjYsK28CJD5z2b7FojMCDg6vERASShVZqAvnsC9LhS7saG8CmMo5Rm92wgnT8wa6nJVu57MHHjmnoyvTpCG7NQ7dErc
**********************************************************************
Use the "help" command to see a simplified list of available commands.
Use "help all" to see the list of all available commands.
Use "help <command>" to see a command's documentation.
**********************************************************************
SigV2DXdetxj9qiRe6PHsch9EwZVutb1FFR38ubNuM9ef8YPYcnjAisLWo4sLZMoT3g4Z48VRD3xAUsk1EcfthWcxnayW
Stripping the prefix SigV2 of SigV2DXdetxj9qiRe6PHsch9EwZVutb1FFR38ubNuM9ef8YPYcnjAisLWo4sLZMoT3g4Z48VRD3xAUsk1EcfthWcxnayW,
we get the base58 representation of the signature. Note that monero's implementation of base58 is different from bitcoin's.
See monero-rs/base58-monero for how to manipulate monero base58 data programatically.
In order for ckb-auth to actually verify the validity of the signature, we need to store the signature,
the mode (only spend key mode is supported) that used to sign the transactions
and public keys (spend key followed by view key).
For example, to verify the signature with base65 encoding 3ZKheximq145tW14dshL17Jpqp2GJn296GfRnGqt3pMeaZU7xoEEAFr2Xm7Jc7xZjYWf6KhstZanA73to7uF6rea
which is signed by the spend key of monero account 41eBLjYsK28CJD5z2b7FojMCDg6vERASShVZqAvnsC9LhS7saG8CmMo5Rm92wgnT8wa6nJVu57MHHjmnoyvTpCG7NQ7dErc
we need to use the data whose hex encoding is
0f49fbc1bee9b7d31d3918a3753af5526a915e1f930198315da3e43bbd32f109c8a40ece34f42ff909263e16bb43f53bb14e5fe90de6c04f242b7c6a73ee320f00007caf7a553a894389dd562115b17e78ba84a5c7692677f216c54385dc5c6ff1bbcb8c902571ae1a777f7f07a023ecc5e3d83ba624d4b0ffb7eff79e8b5d10bd
where the first 64 bytes 0f49fbc1bee9b7d31d3918a3753af5526a915e1f930198315da3e43bbd32f109c8a40ece34f42ff909263e16bb43f53bb14e5fe90de6c04f242b7c6a73ee320f are the signature itself,
the 65th byte is the mode for signing (here 00, which stands for signing with spend key),
the next 64 bytes 007caf7a553a894389dd562115b17e78ba84a5c7692677f216c54385dc5c6ff1bbcb8c902571ae1a777f7f07a023ecc5e3d83ba624d4b0ffb7eff79e8b5d10bd are the public spend key followed by public view key.