SoftForkNewOpcode.sol

pragma solidity ^0.4.0;

// This contract is used for making a new opcode via a softfork.
// It works for opcodes that just evaluate an arbitrary function,
// returning y = f(x).
//
// The idea is to create a contract that implements an arbitrary key-value 
// mapping, but miners (after the softfork) enforce that the only updates to the
// contract respect the correct function.
// 
// To make this easy to enforce, the contract itself enforces that the mappings
// can only be written by a transaction from a user account (but the private
// key for this account is published / well-known).

contract SoftForkNewOpcode {

    // Private key (anyone can spend!): 
    //   9d3cd1335763d4e46a335054a27672aab7edefabdb6111729801c6a55d9350a7
    address constant pk = 0x8f9704c1F3773B49D095217B4577935191Ec8050;

    mapping (bytes32 => bytes32) public data;
    
    function set(bytes32 k, bytes32 v) {
        // This function can only be called by the account above 
        require(msg.sender == pk);
        data[k] = v;
    }
}