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Virtual Machines on the Æternity blockchain

A smart contract is associated with a virtual machine for the execution of that contract. The Æternity blockchain supports the virtual machine AEVM - A version of the Ethereum VM. The AEVM can also use different ABIs, and it is versioned to ensure that runs on earlier version can still be run to validate the chain in the presence of consensus breaking VM changes.

A Create Contract transaction and the contract state tree contains a 'vm_version' field and an 'abi_version' field. These fields describes the type and version of the virtual machine to use for the contract and the type and version of the application binary interface (ABI) of the contract. (Note that the serialization packs the version into one integer.)

The current meaning of the VM field is:

Value (hex) Machine Description
00 none NO_VM ("Used" in oracles)
01 AEVM_01 For Sophia contracts on the AEVM
02 AEVM_01 For Solidity contracts on the AEVM
03 AEVM_02 Improved AEVM for Sophia, Minerva release
04 AEVM_03 Improved AEVM for Sophia, Fortuna release

The current meaning of the ABI field is:

Value (hex) ABI Description
00 raw string No interpretation - used in oracles
01 Sophia_01 For Sophia contracts on the AEVM
02 Solidity_01 For Solidity contracts on the AEVM

Which VM versions are accepted are different based on consensus protocol versions.

Protocol version Operation Accepted VM values Accepted ABI values
Roma contract call/create 0x1 0x1
oracle register (Not applicable.) 0x0, 0x1
Minerva contract call 0x1, 0x3 0x1
contract create 0x3 0x1
oracle register (Not applicable.) 0x0, 0x1
Fortuna contract call 0x1, 0x3, 0x4 0x1
contract create 0x3, 0x4 0x1
oracle register (Not applicable.) 0x0, 0x1

The number after the machine name designates the version of the machine. In the future new versions of the machine can be implemented with new instructions, contracts using these machines must use a new vm_version number corresponding to the new machine version.

The ABI name correspond to the supported languages. All Ethereum VM languages uses the same ABI (Solidity_1). The languages can in the future be extended with new functionality and new ABIs reflected by the ABI version number.

For a description of each ABI see the corresponding language description: Sophia, Solidity, Varna.

The Æternity Ethereum Virtual Machine AEVM

See The AEVM.

Consensus breaking changes between AEVM versions

AEVM_01 -> AEVM_02

  • Oracle query fee of unknown oracle
  • AEVM_01: Succeeded with bogus value
  • AEVM_02: Fails with exception
  • New crypto/hash primitives
  • New VM instructions (bit shift operations)

AEVM_02 -> AEVM_03

  • New primitive operations (Auth.tx_hash)
  • New crypto primitives