# Circuits definitions crate
This crate contains the 'outer layer' for multiple circuits. The concrete circuits code is in `era-zkevm_circuits`
repository.
## Code structure
We have 13 different 'base layer' circuits (for example MainVM, Decomitter), and 3 recursive circuits (Leaf, Node and
Scheduler).
Base layer circuits are located in `src/base_layer`, Recursive circuits are in `src/recursion_layer`.
We also have 'AUX' circuits: compressors and wrapper, that are run on top of the final Scheduler proof, and they are
located in `src/aux_layer`.
`src/encodings` directory contain some helper structs that are used by the test harness (and should match the ones used
in circuits themselves).
## Circuit types
We have 12 different circuit types (in witness, you might notice 13, as one circuit (events_dedup_and_sort) is used for
both L1 messages and events).
| Main VM | vm_main.rs | Executes OpCodes from the VM |
| CodeDecommittmentsSorter | sort_code_decommit.rs | Verifies the order of requests for code decommitment (fetching bytecode based on hash). |
| CodeDecommiter | code_decommiter.rs | Unpacks the bytecode matching a given hash into memory. |
| LogDemuxer | log_demux.rs | Splits the queue into 6 output ones (like keccak, sha, storage). |
| KeccakRoundFunction | keccak256_round_functions.rs | Round of the keccak hash |
| Sha256RoundFunction | sha256_round_function.rs | Round of sha256 hash |
| ECRecover | ecrecover.rs | Verifies ECRecover |
| RAMPermutation | ram_permutation.rs | Verifies the correctness of the RAM accesses - looking at the access queue, and checking that correct bytes values were read |
| StorageSorter | storage_sort_dedup.rs | Similar to RAM permutation, but for storage - checking that correct bytes were stored / read. |
| StorageApplication | storage_apply.rs | Verifies the final merkle root and storage diffs based on the data that was written during computation. |
| EventsSorter | events_sort_dedup.rs | Verifies that a given 'unsorted' queue is matching the sorted one, without any repetitions. In this case, used for System Events. |
| L1MessagesSorter | events_sort_dedup.rs | It reuses the circuit above, but this time to sort user generated events (L2 -> L1 messages). |
| L1MessageHasher | linear_hasher.rs | Verifies that linear hash of L1 messages matches the content of the queue. |
3 recursive circuits:
| Leaf | leaf_layer.rs | Aggregates 32 basic circuits of the same type |
| Node | node_layer.rs | Aggregates 32 leaf (or node) circruits of the same type |
| Scheduler | scheduler.rs | Aggregates 13 nodes (1 from each type) into a final proof |
And 'wrapper'/AUX circuits on top:
| Compression | compression.rs | Compresses the final scheduler proof |
| Wrapper | wrapper.rs | Wraps the compressed proof into a SNARK to be verifierd on L1. (This is a SNARK circuit) |