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System Contracts

System contracts are interfaces defined as contracts, which are essential or recommended for an ewasm VM.

An ewasm VM implementation may opt to implement these interfaces natively or to rely on implementations written in ewasm.

Each of these contracts have a pre defined address and can be executed through regular contract invocations.

Sentinel Contract

Address: 0x000000000000000000000000000000000000000a

Every newly deployed ewasm contract must be processed by the Sentinel Contract prior to including the code in the state. The sentinel will perform three very important processing steps:

  • Validate ewasm semantics
  • Inject metering code
  • Wrap the result in the deployer preamble (see Appendix A)

See the dedicated chapter about it.

EVM Transcompiler

Address: 0x000000000000000000000000000000000000000b

Transcompiles EVM1 bytecode into ewasm bytecode. See the dedicated chapter about it.

The use of this is optional. A compatible client may implement EVM1 natively or may choose to use this transcompiler.

Input:

  • variable length: EVM1 contract code

Output:

  • variable length: ewasm contract code

EVM Precompiled Contracts

Precompiled contracts are defined for EVM1 (see the Yellow Paper). Several extensions have been proposed as Ethereum Improvement Proposals.

We assume the contracts defined in the Yellow Paper still apply for ewasm.

ecrecover

Address: 0x0000000000000000000000000000000000000001

Calculates the corresponding Ethereum address for the public key which created the given signature.

Input:

  • 32 bytes: message hash
  • 32 bytes: recovery id
  • 32 bytes: R component
  • 32 bytes: S component

Output:

  • 32 bytes: Ethereum address (left padded with zeroes)

sha2-256

Address: 0x0000000000000000000000000000000000000002

Returns the SHA2-256 hash of the input.

Input:

  • variable length: input data

Output:

  • 32 bytes: sha2-256 hash

ripemd160

Address: 0x0000000000000000000000000000000000000003

Returns the RIPEMD-160 hash of the input.

Input:

  • variable length: input data

Output:

  • 32 bytes: ripemd160 hash (left padded with zeroes)

identity

Address: 0x0000000000000000000000000000000000000004

Copies the input data to the output.

Input:

  • variable length: input data

Output:

  • variable length: output data

keccak256

Address: 0x0000000000000000000000000000000000000009

Returns the KECCAK-256 hash of the input. It is being used by the EVM Transcompiler.

Input:

  • variable length: input data

Output:

  • 32 bytes: keccak-256 hash

Appendix A: ewasm deployer preamble

;;
;; Standard ewasm deployer code.
;;
;; We keep the to-be-deployed contract as a memory segment and simply return it.
;;

(module
  (memory 1
    (segment 0 "\10\00\00\00")     ;; Here comes the size of the code in LSB
    (segment 4 "Hello World CODE") ;; Here comes the code as a escaped hex string
  )
  (export "memory" memory)
  (export "main" $main)
  (import $ethereum_return "ethereum" "return" (param i32 i32))
  (func $main
    (call_import $ethereum_return (i32.const 4) (i32.load (i32.const 0)))
  )
)