HotStuff types

hotstuff_pseudo_code.hpp

// WIP

namespace eosio::hotstuff {

using sha256         = fc::sha256;
using block_id_type  = eosio::chain::block_id_type;
using bitset         = boost::dynamic_bitset<uint32_t>;
using bls_public_key = fc::crypto::blslib::bls_public_key;
using bls_signature  = fc::crypto::blslib::bls_signature;

struct proposal {
    sha256          parent_proposal;    //< ID of the proposal that is justified by the valid QC that normally must be
                                        //< available prior to creating this proposal.
                                        //< This could be the empty hash to indicate that this proposal has no parent,
                                        //< which is allowed in exceptional situations such as when the transition to 
                                        //< HotStuff consensus first occurs or if the network needs to unsafely 
                                        //< recover liveness from some catastrophic failure.

    block_id_type   head_block; //< ID of the head of the blockchain proposed by this proposal.
                                //< If the parent_proposal is not the empty hash, then head_block must reference a 
                                //< block that is or extends the block referenced by the head_block of the proposal 
                                //< referenced by parent_proposal.

    block_id_type   final_on_qc;    //< ID of the latest block that is in the branch defined by head_block that will
                                    //< be considered final once a valid QC is available for this proposal.
                                    //< If parent_proposal is the empty hash, there would not be a long enough QC
                                    //< chain to advance finality of the blockchain, but final_on_qc should reference 
                                    //< the last known final block in the branch defined by head_block.

    uint64_t        view;   //< View number for this proposal.
                            //< Assume time_bound is the number of milliseconds (rounded up) since UNIX epoch for
                            //< the block timestamp captured in the block referenced by head_block.
                            //< Assuming p is a proposal where p.proposal_id() == parent_proposal:
                            //<    Then, view must be greater than p.view but less than time_bound.
                            //<    If possible, view should ideally be equal to p.view + 1.
                            //<    If that is not possible, then the next best value for the view (assuming allowed
                            //<    by the constraints) is the number of milliseconds (rounded up) since UNIX epoch
                            //<    for the block timestamp captured in the block one previous to the block referenced
                            //<    by head_block.
                            //< If such a p does not exist since parent_proposal is the empty hash,
                            //< then view must be equal to time_bound.

    uint64_t        active_generation;  //< Generation number for the finalizer set that is active at the start of 
                                        //< this proposal. 
                                        //< That active finalizer set must be used as the QC signature on this
                                        //< proposal's proposal_id().
                                        //< Assuming p is a proposal where p.proposal_id() == parent_proposal:
                                        //<     Then, active_generation must be equal to p.next_active_generation.
                                        //< If such a p does not exist since parent_proposal is the empty hash,
                                        //< then active_generation must be equal to the highest generation number of
                                        //< the proposed finalizer sets available in the block header extensions for
                                        //< the blockchain accessible from the block referenced by final_on_qc.

    uint64_t        next_active_generation; //< Generation number for the finalizer set to be considered active for
                                            //< the next proposal that references this proposal assuming a valid QC is
                                            //< available for this proposal.
                                            //< Assuming p is a proposal where p.proposal_id() == parent_proposal:
                                            //<     Then, next_active_generation must be greater than or equal to 
                                            //<     p.next_active_generation.
                                            //<     It must be set to the highest generation number of the proposed
                                            //<     finalizer sets available in the block header extensions for the
                                            //<     blockchain accessible from the block referenced by final_on_qc.
                                            //< If such a p does not exist since parent_proposal is the empty hash,
                                            //< then next_active_generation must be equal to active_generation.

   sha256 proposal_id() const; // Computes SHA256 digest of a serialization of the variables above within this struct.
}

struct quorum_certificate_signature {
    bitset          present_finalizers;
    bls_signature   aggregate_signature;
};

struct quorum_certificate {
    sha256                          proposal_id;
    quorum_certificate_signature    qc_sig; //< QC signature on proposal_id.
                                            //< qc_sig.present_finalizers bitset references the finalizer set with
                                            //< generation number equal to p.active_generation where p is a proposal
                                            //< such that p.proposal_id() == proposal_id.
};

} // namespace eosio::hotstuff



namespace eosio::chain {

namespace hs = eosio::hotstuff;

struct hs_proposal_message {
    hs::proposal                        proposal;
    hs::quorum_certificate_signature    qc_sig; //< QC signature on proposal.parent_proposal.
                                                //< qc_sig.present_finalizers bitset references the finalizer set with
                                                //< generation number equal to p.active_generation where p is a
                                                //< proposal such that p.proposal_id() == proposal.parent_proposal.
                                          
};

struct hs_vote_message {
    fc::sha256                      proposal_id;
    hs::bls_public_key              pub_key;
    hs::bls_signature               sig;    // Signature sig must be on proposal_id validated with public key pub_key.

};

struct hs_new_view_message {
    hs::quorum_certificate   high_qc;
};

} // namespace eosio::chain