Typed data hashing and signing

Common structure

The whole idea is heavily inspired by EIP-712. To get a signature needed to calculate hash(hash(domain), hash(aci), hash(data)).

hash function is blake2b.

domain is a record containing not required properties:

• name as string,

• version as integer,

• networkId as string,

• contractAddress as ct-encoded string.

aci is part of a complete contract ACI. It defines a type of data to sign. For example, the ACI

{
  "record": [
    { "name": "foo", "type": "string" },
    { "name": "bar", "type": "int" }
  ]
}

corresponds to the data

{ "foo": "test", "bar": 42 }

domain and data are fate-encoded before hashing. aci is prepared for hashing according to RFC8785.

Implementation

• AccountBase:signTypedData — calculates signature, supported in AccountMemory and in aepp-wallet connection;
• hashTypedData — calculates the overall hash of typed data to sign;
• hashJson — deterministic hashing of an arbitrary JS value, used to calculate hash(aci);
• hashDomain — use for debugging or to prepare the hash value for smart contract.

Examples

• signing and verifying on aepp side
• signing confirmation on wallet side
• verifying a signature on contract side