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What is a certificate?

Cross-subnet communication in Topos lies in the submission of certificates—data structures that certify subnet state transitions.

It is the role of every subnet to:

Once broadcast and delivered throughout the TCE, the certificate can be verified and the cross-subnet message executed in the receiving subnet.


A certificate is defined as:

  • subnet_id is the unique identifier of the subnet;
  • prev_state_hash is the previous subnet state commitment (from the previous certificate);
  • state_hash is the current subnet state commitment;
  • proof is the zkSTARK proof of validity;
  • XS_list represents the list of included cross-subnet messages;
  • proof_XS_list is the list of inclusion proofs of cross-subnet messages in the proven state transition;