EIP-170: Contract code size limit


  Ethereum Improvement Proposals
        
        
          
            
              
            
          
        

        AllCoreNetworkingInterfaceERCMetaInformational

      



      
        
  
    

  
    
    
    
    
    
      Standards Track: Core
    
  
  
    
      EIP-170: Contract code size limit
    
    
      
        
      
    
    
      
        
      
    
  

  

  	Authors	Vitalik Buterin (@vbuterin)
	Created	2016-11-04


  


  

  
    Table of Contents

    	Hard fork
	Parameters
	Specification
	Rationale
	References



  


  
      
      
         Hard fork
      
      
    

Spurious Dragon

  
    
      
      
         Parameters
      
      
    

	MAX_CODE_SIZE: 0x6000 (2**14 + 2**13)
	FORK_BLKNUM: 2,675,000
	CHAIN_ID: 1 (Mainnet)


  
    
      
      
         Specification
      
      
    


If block.number >= FORK_BLKNUM, then if contract creation initialization returns data with length of more than MAX_CODE_SIZE bytes, contract creation fails with an out of gas error.

  
    
      
      
         Rationale
      
      
    


Currently, there remains one slight quadratic vulnerability in Ethereum: when a contract is called, even though the call takes a constant amount of gas, the call can trigger O(n) cost in terms of reading the code from disk, preprocessing the code for VM execution, and also adding O(n) data to the Merkle proof for the block’s proof-of-validity. At current gas levels, this is acceptable even if suboptimal. At the higher gas levels that could be triggered in the future, possibly very soon due to dynamic gas limit rules, this would become a greater concern—not nearly as serious as recent denial of service attacks, but still inconvenient especially for future light clients verifying proofs of validity or invalidity. The solution is to put a hard cap on the size of an object that can be saved to the blockchain, and do so non-disruptively by setting the cap at a value slightly higher than what is feasible with current gas limits.

  
    
      
      
         References
      
      
    


	EIP-170 issue and discussion: https://github.com/ethereum/EIPs/issues/170
	pyethereum implementation: https://github.com/ethereum/pyethereum/blob/5217294871283d8dc4fb3ca9d8a78c7d416490e8/ethereum/messages.py#L397



  Citation

  Please cite this document as:

  
  Vitalik Buterin (@vbuterin), "EIP-170: Contract code size limit," Ethereum Improvement Proposals, no. 170, November 2016. [Online serial]. Available: https://eips.ethereum.org/EIPS/eip-170.






      
    
  

  

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        Ethereum Improvement Proposals (EIPs) describe standards for the Ethereum platform, including core protocol specifications, client APIs, and contract standards.