P4-commentary.txt

                      Protocol update commentary

Protocol Version: 4
Builds on Protocol Version: 3
Protocol Name: Sirius

Protocol version 4 adds support for two major features, delegation and
improved smart contracts.

In the delegation model in protocol version 4, bakers can open pools,
and accounts can delegate part of their capital to such a pool.
Rewards for baking are distributed proportionally to each pool’s
stake. The baker gets a portion of the pool rewards, the remaining
rewards are then distributed amongst the pool participants,
proportionally to their stake. To ensure security of the chain each
pool has a leverage bound, ensuring bakers have to stake a minimum
amount of their own capital, and there is a global bound to ensure no
pool grows too large relative to all other pools.

The smart contracts are updated by adding a new variant, version 1
contracts. The new smart contracts expand the range of use-cases
supported on the concordium chain, make it easier to build smart
contracts that interact with other contracts, and natively support
cryptographic functions `verify_ed25519_signature`,
`verify_ecdsa_secp256k1_signature`, `hash_sha2_256`, `hash_sha3_256`,
and `hash_keccak_256`.

The key technical features of the new contracts are unlimited contract
state based on a key-value store API, synchronous contract calls to
make it simpler to interact with other contracts, and increased
contract size allowance. Version 1 contracts can also support fallback
or default entrypoints to enable easier building of proxy contracts.

Existing version 0 contracts will retain their semantics and continue
to function as they have. New version 0 contracts can still be
created.