Key Management¶

Securely managing keys is of utmost importance in any blockchain, including Mavryk, because keys are used to sign sensitive operations such as transfers of valuable assets (mav, FA tokens, tickets, …) or baking operations.

The Mavkit tool suite offers several solutions to store your private keys safely and use them securely for signing operations. However, these solutions are not enabled by default, so you have to turn them on, as explained in this tutorial.

Indeed, by default:

Private keys are stored unencrypted in file $MAVKIT_CLIENT_DIR/secret_keys.
The client uses these keys to sign user operations (e.g. transfers) by itself.
The baker daemon uses these keys to automatically sign its operations (e.g. (pre-)attestations).

The solutions provided to strengthen the security of the default key management and signing are the following:

A hardware wallet (highly recommended) allows to:
- store your private keys securely
- sign user operations (e.g. transfers) interactively on the wallet
- automatically sign baking operations, such as (pre-)attestations, more securely.
If you don’t have a hardware wallet, the option --encrypted of the client offers a first protection for storing your keys.
A separate signer daemon allows to decouple the client and baker from the signing process.

In particular, this allows executing the signer remotely (that is, on a different machine than the client and/or the baker), perhaps less exposed to attacks.

As the keys only need to be accessible to the signer, they can also benefit from the lesser exposure. Even better (and recommended), a remote signer can be combined with a hardware wallet connected to the same machine as the signer.

These solutions are detailed in the rest of this page.

Ledger support¶

It is possible and advised to use a hardware wallet to securely store and manage your keys. The Mavkit client supports Ledger Nano devices provided that they have a Mavryk app installed. The apps were developed by Obsidian Systems and they provide a comprehensive tutorial on how to install it.

Ledger Manager¶

The preferred way to set up your Ledger is to install Ledger Live. On Linux make sure you correctly set up your udev rules as explained here. Connect your Ledger, unlock it and go to the dashboard. In Ledger Live install Mavryk Wallet from the applications list and open it on the device.

Mavryk Wallet app¶

Now on the Mavkit client we can import the keys (make sure the device is in the Mavryk Wallet app):

./mavkit-client list connected ledgers

This will display some instructions to import the Ledger encrypted private key, and you can choose between the root or a derived address. We can follow the instructions and then confirm the addition by listing known addresses:

./mavkit-client import secret key my_ledger ledger://XXXXXXXXXX
./mavkit-client list known addresses

Optional: we can check that our Ledger signs correctly using the following command and confirming on the device:

mavkit-client show ledger ledger://XXXXXXXXXX --test-sign

The address can now be used as any other with the exception that during an operation the device will prompt you to confirm when it’s time to sign an operation.

Mavryk Baking app¶

In Ledger Live (with Developer Mode enabled), there is also a Mavryk Baking app which allows a delegate to sign automatically (i.e., there is no need to manually sign every block or (pre-)attestation). Of course, the application is restricted to only sign baking operations; it never signs a transfer, for example. Furthermore, the application keeps track of the last level baked and only allows baking for subsequent levels. This prevents signing blocks at levels below the latest block signed.

If you have tried the app on some network and want to use it on another network you might need to reset this level with the command:

mavkit-client setup ledger to bake for my_ledger

More details can be found on the Mavryk Ledger app.

Signer¶

A solution to decouple the client and the baker from the signing process is to use a remote signer.

In this configuration, the client sends signing requests over a communication channel towards mavkit-signer, which can run on a different machine that stores the secret key.

There are several signing schemes supported by the client, corresponding to different communication channels, such as unix, tcp, http and https. We can list the available schemes with:

mavkit-client list signing schemes

We now explain how this remote signer configuration works based on signing requests, how can it be set up, and how the connection to the signer can be secured (as by default it is not secure).

Signer requests¶

The mavkit-signer handles signing requests with the following format:

<magic_byte><data>

In the case of blocks or consensus operations for example, this format is instantiated as follows:

<magic_byte><chain_id><block|consensus_operation>

Consensus operations also include preattestations. The magic byte distinguishes messages, as follows:

Message type	Magic byte
Legacy block	0x01
Legacy endorsement	0x02
Transfer	0x03
Authenticated signing request	0x04
Michelson data	0x05
Block	0x11
Pre-attestation	0x12
Attestation	0x13

The magic byte values to be used by the signer can be restricted using its option --magic-bytes, as explained in the signer’s manual.

Signer configuration¶

In our home server we can generate a new key pair (or import one from a Ledger) and launch a signer that signs operations using these keys. To select the tcp signing scheme, one has to launch mavkit-signer with the socket argument, as shown below. The new keys are stored by the signer in $HOME/.mavkit-signer in the same format as mavkit-client. On our internet-facing virtual private server, called “vps” here, we can then import a key with the address of the signer.

home~$ mavkit-signer gen keys alice
home~$ cat ~/.mavkit-signer/public_key_hashs
[ { "name": "alice", "value": "mv1abc..." } ]
home~$ mavkit-signer launch socket signer -a home

vps~$ mavkit-client import secret key alice tcp://home:7732/mv1abc...
vps~$ mavkit-client sign bytes 0x03 for alice

Every time the client on vps needs to sign an operation for alice, it sends a signature request to the remote signer on home.

However, with the above method, the address of the signer is hard-coded into the remote key value. Consequently, if we ever have to move the signer to another machine or access it using another protocol, we will have to change all the remote keys. A more flexible method is to only register a key as being remote, and separately supply the address of the signer using the -R option:

vps~$ mavkit-client -R 'tcp://home:7732' import secret key alice remote:mv1abc...
vps~$ mavkit-client -R 'tcp://home:7732' sign bytes 0x03 for alice

Alternatively, the address of the signer can be recorded in environment variables:

vps~$ export MAVRYK_SIGNER_TCP_HOST=home
vps~$ export MAVRYK_SIGNER_TCP_PORT=7732
vps~$ mavkit-client import secret key alice remote:mv1abc...
vps~$ mavkit-client sign bytes 0x03 for alice

All the above methods can also be used with the other signing schemes, for instance, http:

home~$ mavkit-signer launch http signer -a home

vps~$ mavkit-client import secret key alice http://home:7732/mv1abc...
vps~$ mavkit-client sign bytes 0x03 for alice

vps~$ mavkit-client -R 'http://home:7732' import secret key alice remote:mv1abc...
vps~$ mavkit-client -R 'http://home:7732' sign bytes 0x03 for alice

vps~$ export MAVRYK_SIGNER_HTTP_HOST=home
vps~$ export MAVRYK_SIGNER_HTTP_PORT=7732
vps~$ mavkit-client import secret key alice remote:mv1abc...
vps~$ mavkit-client sign bytes 0x03 for alice

The complete list of environment variables for connecting to the remote signer is:

MAVRYK_SIGNER_TCP_HOST
MAVRYK_SIGNER_TCP_PORT (default: 7732)
MAVRYK_SIGNER_HTTP_HOST
MAVRYK_SIGNER_HTTP_PORT (default: 6732)
MAVRYK_SIGNER_HTTPS_HOST
MAVRYK_SIGNER_HTTPS_PORT (default: 443)
MAVRYK_SIGNER_UNIX_PATH
MAVRYK_SIGNER_HTTP_HEADERS

Secure the connection¶

Note that the above setup alone is not secure, the signer accepts requests from anybody and happily signs any transaction!

Improving the security of the communication channel can be done at the system level by setting up a tunnel with ssh or wireguard between home and vps.

The signer itself can also be configured to provide additional protection. With the option --require-authentication the signer requires the client to authenticate before signing any operation.

First we create a new key on the vps and then import it as an authorized key on home where it is stored under .mavkit-signer/authorized_keys (similarly to ssh). Note that this key is only used to authenticate the client to the signer and it is not used as a Mavryk account.

vps~$ mavkit-client gen keys vps
vps~$ cat ~/.mavryk-client/public_keys
[ { "name": "vps",
    "value":
       "unencrypted:edpk123456789" } ]

home~$ mavkit-signer add authorized key edpk123456789 --name vps
home~$ mavkit-signer --require-authentication launch socket signer -a home-ip

All request are now signed with the vps key, guaranteeing their authenticity and integrity. However, this setup does not guarantee confidentiality: an eavesdropper can see the transactions that you sign (on a public blockchain this may be less of a concern). In order to avoid that, you can use the https scheme or a tunnel to encrypt your traffic.

Consensus Key¶

By default, the baker’s key, also called manager key, is used to sign in the consensus protocol, i.e. signing blocks while baking, and signing consensus operations (preattestations and attestations).

A delegate may elect instead to choose a dedicated key: the consensus key. It can then be changed without redelegation.

It also allows establishment of baking operations in an environment where access is not ultimately guaranteed: for example, a cloud platform providing hosted Key Management Systems (KMS) where the private key is generated within the system and can never be downloaded by the operator. The delegate can designate such a KMS key as its consensus key. Shall they lose access to the cloud platform for any reason, they can simply switch to a new key.

However, both the delegate key and the consensus key give total control over the delegate’s funds: indeed, the consensus key may sign a Drain operation to transfer the delegate’s free balance to an arbitrary account.

As a consequence, the consensus key should be treated with equal care as the manager key.

Registering a Consensus Key¶

A consensus key can be changed at any point.

The operation is signed by the manager key and does not require the consensus private key to be accessible by the client.

However the public key must be known by the client. It can be imported with the command:

mavkit-client import public key consensus unencrypted:edpk...

The command to update the consensus key is:

mavkit-client set consensus key for <mgr> to consensus

The update becomes active after CONSENSUS_RIGHTS_DELAY + 1 cycles. We therefore distinguish the active consensus key and the pending consensus keys. The active consensus key is by default the delegate’s manager key, which cannot change.

However, it is also possible to register as a delegate and immediately set the consensus key:

mavkit-client register key <mgr> as delegate with consensus key <key>

There can be multiple pending updates: it is possible to have multiple pending consensus keys for multiple future cycles. A subsequent update within the same cycle takes precedences over the initial one.

Baking With a Consensus Key¶

In your baker’s command, replace the delegate’s manager key alias with the consenus key alias:

mavkit-baker-Ptxxxxxx run with local node ~/.mavryk-node <consensus_key_alias> --liquidity-baking-toggle-vote pass

While transitioning from the delegate’s manager key, it is possible to pass the alias for both delegate’s manager key and consensus key. The delegate will seamlessly keep baking when the transition happens:

mavkit-baker-Ptxxxxxx run with local node ~/.mavryk-node <consensus_key_alias> <delegate_key_alias> --liquidity-baking-toggle-vote pass

Draining a Manager’s Account With its Consensus Key¶

This operation immediately transfers all the spendable balance of the baker_pkh’s implicit account into the destination_pkh implicit account:

mavkit-client drain delegate <baker_pkh> to <destination_pkh> with <consensus_pkh>

If the destination is the consensus key account, this can be simplified to:

mavkit-client drain delegate <baker_pkh> to <consensus_pkh>

The active consensus key is the signer for this operation, therefore the private key associated to the consensus key must be available in the wallet of the client typing the command. The delegate’s private key does not need to be present.

The drain operation has no effect on the frozen balance.

A fixed fraction of the drained delegate’s spendable balance is transferred as fees to the baker that includes the operation, i.e. the maximum between 1 mav or 1% of the spendable balance.

Getting keys for fundraiser accounts¶

If you took part in the fundraiser but didn’t yet activate your account, it is still possible to activate your Mainnet account on https://check.tezos.com/. This feature is also included in some wallets. If you have any questions or issues, refer to that page or to the Mavryk Foundation for support.

You may also use mavkit-client to activate your account, but be warned that you should have a very good understanding of key management in Mavryk and be familiar with the command-line. The first step is to recover your private key using the following command which will ask for:

the email address used during the fundraiser
the 14 words mnemonic of your paper wallet
the password used to protect the paper wallet

mavkit-client import fundraiser key alice

Once you insert all the required information, the client computes your secret key and it asks you to create a new password in order to store your secret key on disk encrypted.

If you haven’t already activated your account on the website, you can use this command with the activation code obtained from the Mavryk foundation.

mavkit-client activate fundraiser account alice with <code>

Check the balance with:

mavkit-client get balance for alice

As explained above, your keys are stored under ~/.mavryk-client. We strongly advise you to first make a backup and then transfer your tokens to a new pair of keys imported from a Ledger (see Ledger support).