Engine

Holds FCT's engine information

Typed Struct (EIP712)

Engine(bytes4 selector,bytes3 version,bytes3 random_id,bool eip712,string verifier,bool auth_enabled,bool dry_run)

Params

Name	Type
selector	bytes4
version	bytes3
random_id	bytes3
eip712	bool
verifier	string
auth_enabled	bool
dry_run	bool

selector

Holds the FCT Engine called function selector, the first four bytes of the Keccak-256 hash of the signature of the batchMultiSigCall function inside the FCT_BatchMultiSig contract.

Must be "0xb91c650e" for current FCT_BatchMultiSig interface

version

Holds the version number of a specific implementation of the FCT Engine called function

FCT supports using different implementation of the same interface by adding version numbers resulting in an "extended function selector".

FCT follows the Semantic Versioning standard: 0xMMmmpp MM - Major Version (up-to 256 values) mm - Minor Version (up-to 256 values) pp - Patch Version (up-to 256 values)

0x010A04 represents version 1.10.4

FCT Engine will preserve backward compatibility for minor and patch version changes while major version changes indicates breaking changes

The FCT_Runner gets the interface and version before executing and can implement any versioning logic. See "vault versioning" for current vault implementation

random_id

FCT protects against double spending by keeping the hashes of executed messages.

In order to enable executing FCTs that holds the exactly same content more than once, without using the recurrency feature, there is a need to make all FCT's hashes unique. In order to do that, every FCT message holds a free random value.

random_id may hold any number between 0 and 16777215 represented by bytes3 value

random_id is relevant only in the case where all fields of two FCTs holds exactly the same values, e.g. sending the same amount to the same address

eip712

A boolean that tells the FCT Engine, the message format, the current FCT was signed. If the value is true, FCT is expected to be formatted as a standard EIP-712 message. If this values if false, FCT is expected to be formatted as a standard EIP-191 message

verifier

Users can set a 3rd party verifier that needs to sign of the FCT in order to make it valid.

Anti-AML and scam protection services can use this field to give protection to their users.

auth_enabled

A boolean that tells the FCT Engine, to make sure only official known runners are being used.

When there is more than one participant on the FCT, it is highly recommended to set this flag on.

dry_run

A boolean that tells the FCT Engine to always fail, returning special revert message on successful execution of the fct, or passing the existing revert message when execution fails.

Dry run is being used to provide off chain alerts for customised on-chain data.