[Elephant] Feature: Mosaic Restrictions

[evias]

In catapult, mosaic creators should be allowed to set constraints on accounts that can transact with their defined mosaics.

This functionality will be enabled by a new mosaic property Constrainable that will be disabled by default. Constraints are undesirable for completely fungible tokens (like XEM).

In order to assign a constraint, a new mosaic constraint transaction is required.

We will be adding a new transaction type MosaicRestrictionTransaction to be defined in catapult-server. With following specificities:

• The mosaic creator of the affected mosaic must be signer of this transaction.
• MosaicRestrictionType is only applicable to global mosaic constraints (0-Address for Target). When setting on specific account, the constraint type must be EQ.

A constraint will be defined by a list of custom properties as defined in following table (counter-check with catapult-server needed for confirmation.)

Mosaic Address Restriction

• Version: 1
• EntityType: 0x4251

Field	Type	Description
mosaicId	MosaicId	Identifier of the mosaic to which the restriction applies
restrictionKey	uint64_t	Restriction key
targetAdderss	Address or 0-Address	Affected address (zero address to set global mosaic instead of account-specific property)
previousRestrictionValue	uint64_t	Previous restriction value
newRestrictionValue	uint64_t	New restriction value

Mosaic Global Restriction

• Version: 1
• EntityType: 0x4151

Field	Type	Description
mosaicId	MosaicId	Identifier of the mosaic to which the restriction applies
referenceMosaicId	MosaicId	Identifier of the mosaic providing the restriction key
restrictionKey	uint64_t	Restriction key
previousRestrictionValue	uint64_t	Previous restriction value
previousRestrictionType	MosaicRestrictionType	Previous restriction type
newRestrictionValue	uint64_t	New restriction value
newRestrictionType	MosaicRestrictionType	New restriction type

MosaicRestrictionType

• value: uint8_t

Type	Decimal Value	Description
NONE	0	Uninitialized value indicating no restriction
EQ	1	Must be exact match
NE	2	Must not equal
LT	3	Must be less than
LE	4	Must be less than or equal
GT	5	Must be greater than
GE	6	Must be less than or equal

MosaicPropertyFlag

• Type: uint8
  A new flag Restrictable is added,

PropertyName	Value	Description
none	0x00	No flags present
supplyMutable	0x01	Mosaic supports supply changes even when mosaic owner owns partial supply
transferable	0x02	Mosaic supports transfers between arbitrary accounts
restrictable	0x04	Mosaic supports custom restrictions configured by mosaic owner