- Witness Key: Only allows update signing key and publish price feed
- Trading Key: Only allows limit orders (arguments restricted to desired markets), update margin position and transfers (arguments restricted to certain accounts)
- Proposal Update Key: Approve proposals (2FA comes to mind)
Note: The user can still use the active authority just like used to, no change in existing behavior. The named keys only give an additional possibility. For example: The user can login the UI using the private key of such a named key. Then he only as access to the operations that this named key grants. He can still login with the existing password to gain full access (similar a local wallet can be created that only contains the named key).
This BSIP will be split into three parts that will be voted on separately (see Milestones section). All of the above keys are possible with Milestone 1. Milestone 2 allows stateful restrictions (e.g. allow market orders up to some amount for every month), Milestone 3 gives finer control of how to combine restrictions. Milestone 2 and 3 will be put up for voting if Milestone 1 proves successful.
Custom active permission is a list of `custom active authorities`. A `custom active authority` contains an `operation_id`, an `authority` (just like with active permission) and `restrictions` than can be used to restrict arguments and is only valid a certain time period (`valid_from` and `valid_to`). When handling incoming signed transactions, the backend checks for each operation if there is a `custom active authority` for any of its required accounts. Check for every required account of the transaction if all its belonging operations have at least one positively matched `custom active authority` (match means its `authority` is granted through present signatures, same `operation_id`, now is within `valid_to` and `valid_from` and none of the `restrictions` is violated), and if so grant the active authority of the corresponding account.
All descriptions in this section are on a pseudo/prosa level and no recommendation how it can best be implemented or serialized. They are meant to facilitate the understanding. If anything in the looping process or order of evaluation is unsuitable for actual implementation, changes can be made accordingly as long the same functionality is achieved.
Note: This assumes `custom_active_permission` is stored in a separate index. Actual implementation details left to the implementer, as long as every `custom_active_permission` can be assigned to exactly one account.
is called a restriction, that can assert itself positively (passed) or negatively (violated). All restrictions are evaluated per default with `AND` logic to determine if the whole list has asserted positively.
- if there is no value given (e.g. an optional argument, or nested value not given), the restrictions is passed (even if the underlying operation understands the absence of a key as instructions to delete it on-chain, see bitshares/bitshares-core#838)
- if the expected type of the argument does not match the given type (no implicit type conversion), the restriction is violated (needed for nested `attribute_assert`)
Stateful assert, only `int` type arguments. When the authority is created, `interval_began` is set to `valid_from` from its custom active authority and `max_cumsum` to `0`. Incoming operations are first tried to match all stateless asserts,
and if all passes continue with stateful asserts. If `now > interval_began + interval_in_sec`, then set `max_cumsum = 0` and set `interval_began = now`.
The assert that needs to pass is now `current_cumsum + incoming value <= max_cumsum`. If all `asserts` of this `custom_active_authority` pass, update `current_cumsum = current_cumsum + incoming value`.
Stateful assert, only `int` type arguments. Analogue to `limit`, but `interval_began` is initially set to `month(valid_from)` and set to `month(now)` on update, additionally the time assert is `month(now) >= interval_began + interval_in_months` (include logic for month overflow when year changes). The `month(now)` call assumes zulu time to calculate month number.
Stateless assert, only for dictionary type objects. The data list contains restrictions that all must pass, the reference for the `argument` of the child restriction is nested into the attributes of the parent dictionary type object. Allows nesting of `attribute_assert`.
`data = [ [restriction 1, restriction 2], [restriction 3, restriction 4], ... ]`. If one of the restrictions sub-lists in data passes as whole, this restriction passes. In above miniexample that would mean if `restriction 1` and `restriction 2` pass, the whole `logical_or` restriction is considered to be passed as well.
- iterate over all `operations` (child operations of proposal are not included) within the transactions that require the active authority of this account
Adding a custom active authority means increased effort for the backend, and with a stateful one also the need for more storage. Proposed transaction fees:
-`install_custom_active_authority`: Normal accounts can only create custom active authoritites with a duration of maximum 1 year, LTM can do any duration. Two options come to mind:
- A fixed high fee independent of authorities content
- Tied to the duration and complexity of the custom active authority. Transaction fee is then `fee = flat_fee + basic_fee * duration` where `basic_fee` is calculated according to complexity (e.g. size of authority, number of restrictions and etc.). Fee is capped at 1 year for LTM.
* Add a new index or extend the account object to store custom active permission are assigned to an account and contain a list of custom active authorities. Multiple custom active authority entries are possible for one operation
* Provide operations: `install_custom_active_authority`, `update_custom_active_authority`, `delete_custom_active_authority` to allow changing the custom active permission (3 operation to allow custom transaction fees and avoid having to send the complete list of all authorities for every update)
* If the active authority of the account is updated, all custom active authorities are disabled and must be manually specified / re-enabled. User can either
1. keep the authorities enabled by specifying them in a list of `custom_active_authorities` in `extensions` of `account_update_operation`
2. enable them again afterwards by using `update_custom_active_authority`
Assume `asset_update_operation`. All attributes of its `options` must be filled on update call. This assert can not be used to realize a "may only change attribute xzy of `options`". This would require that the logic knows which of the arguments are reflected on-chain and it knows how to query it for every operation that contains `options`. If `options` are to be restricted with this assert, all values that should not change would need be fixated by defining an `any` assert for those attributes, while having e.g. a `lt` assert for the one attribute that is allowed to change.
The custom active authority should be put such that a transfer transaction sending funds away from A can be signed with key K, as long as the receiver is B. More concrete, the authority would look like
- Create a proposal that includes operation 'transfer asset X with amount Y from account A to account B', signed with Key K: Accepted. Anyone can create a proposal.
We propose do split the implmentation into two milestones. Each milestone will be voted on as a separate BSIP:
1. Implementation of basic functionaliy to allow custom active permissions and authorities, including `any`, `none` and `lt, le, gt, ge` and `attribute_assert``asserts`. If deemed necessary by developpers, reduce to only allow one key or one account for every `custom active authority`
2. Implement stateful asserts `limit` and `limit_monthly`
3. Implement `logical_or`
This approach allows as well to add other asserts at a later stage (with a new BSIP).
Bad publicity in terms of security can have very negative effect on the BTS value. This BSIP allows that traders can e.g. use a trading key, witnesses can use their witness key and a faucet can use a faucet key. If then for some reason the key or witness/faucet server becomes compromised, such a key can do little harm to the account holders, minimizing the risk.
This BSIP opens up a lot of use-cases as presented in Motivation section. The intention is to not alter any existing logic of the permission system, which reduces the risk of malfunctioning.
