EIP-1482: Define a maximum block timestamp drift


  Ethereum Improvement Proposals
        
        
          
            
              
            
          
        

        AllCoreNetworkingInterfaceERCMetaInformational

      



      
        
  
    

  
    
      🚧 Stagnant
    
    
    
    
    
      Standards Track: Core
    
  
  
    
      EIP-1482: Define a maximum block timestamp drift
    
    
      
        
      
    
    
      
        
      
    
  

  

  	Authors	Maurelian (@Maurelian)
	Created	2018-10-09
	Discussion Link	https://ethereum-magicians.org/t/define-a-maximum-block-timestamp-drift/1556


  


  

  
    Table of Contents

    	Simple Summary
	Abstract
	Motivation
	Specification
	Rationale
	Backwards Compatibility
	Test Cases
	Implementation
	Copyright



  


  
      
      
         Simple Summary
      
      
    


Include an explicit definition of the acceptable timestamp drift in the protocol specification.

  
    
      
      
         Abstract
      
      
    


On the basis that both Geth and Parity implement the same timestamp validation requirements, this should be written into the reference specification.

  
    
      
      
         Motivation
      
      
    


There is a lack of clarity about how accurate timestamps in the block header must be. The yellow paper describes the timestamp as



  A scalar value equal to the reasonable output of Unix’s time() at this block’s inception




This causes confusion about the safe use of the TIMESTAMP opcode (solidity’s block.timestamp or now) in smart contract development.


Differing interpretations of ‘reasonable’ may create a risk of consenus failures.

  
    
      
      
         Specification
      
      
    


The yellow paper should define a timestamp as:



  A scalar value equal to the output of Unix’s time() at this block’s inception. For the purpose of block validation, it must be greater than the previous block’s timestamp, and no more than 15 seconds greater than system time.



  
    
      
      
         Rationale
      
      
    


Both Geth and Parity reject blocks with timestamp more than 15 seconds in the future. This establishes a defacto standard, which should be made explicit in the reference specification.

  
    
      
      
         Backwards Compatibility
      
      
    


It may be necessary to relax this requirement for blocks which were mined early in the main chain’s history, if they would be considered invalid.

  
    
      
      
         Test Cases
      
      
    


These would be important to have.

  
    
      
      
         Implementation
      
      
    

_The implementations must be completed before any EIP is given status “Final”, but it need not be completed before the EIP is accepted. While there is merit to the approach of reaching consensus on the specification and rationale before writing code, the principle of “rough consensus and running code” is still useful when it comes to resolving many discussions of API details.
_

  
    
      
      
         Copyright
      
      
    

Copyright and related rights waived via CC0.


  Citation

  Please cite this document as:

  
  Maurelian (@Maurelian), "EIP-1482: Define a maximum block timestamp drift [DRAFT]," Ethereum Improvement Proposals, no. 1482, October 2018. [Online serial]. Available: https://eips.ethereum.org/EIPS/eip-1482.






      
    
  

  

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