[RSA Accumulator] Add impl & test

[nrryuya]

References

• This is based on The Matter Inc.'s implementation in Solidity. (gist)

• Other references of big integer arithmetic

  • https://github.com/zcoinofficial/solidity-BigNumber
  • axic/BigInt.sol

[nrryuya]

Code size issue

Fow now, the code can't be deployed due to the excess of the code size: eth.exceptions.OutOfGas: Contract code size exceeds EIP170 limit of 24577. Got code of size: 55782

• The size of the Solidity implementation is 6713 with Remix IDE.

• The size of the code of big integer arithmetic is around 30000...

For analysis.

• LLL of Vyper version
• Assembly of Solidity version

Suspects

• Apparently, there are a tremendous number of mstore and mload in the LLL.

  • For example, the first part in the LLL of def _convertBytesArrayToUInt256List(_inp: bytes[256]) -> uint256[8]: has a sequence of 231 of mload.

                  [mload, 320],
                  [mload, 352],
                  [mload, 384],
                  [mload, 416],
                  [mload, 448],
                  [mload, 480],
                  [mload, 512],
                  [mload, 544],
                  [mload, 576],
                  [mload, 608],
                  [mload, 640],
                  [mload, 672],
    # Continuing...

• The code below in Line 225 is compiled to a complicated LLL

  multiplicationResult = _primes[4 * i] * _primes[4 * i + 1] * _primes[4 * i + 2] * _primes[4 * i + 3]

[jacqueswww]

@nrryuya Yes we really need to have some discussion about what we can do here to reduce bytecode size, I don't think pass by reference is a secure paradigm (as always happy to be convinced otherwise). However as suggested by @charles-cooper we can looking in supporting "final" or immutable structs.