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EIP 55: Mixed-case checksum address encoding

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Note: The following is an excerpt from the official Ethereum site. It is provided here as a convenience and is not authoritative. Refer to the original document as the authoritative reference.
Table 1: Data sheet for Mixed-case checksum address encoding
Title Mixed-case checksum address encoding
Author Vitalik Buterin, Alex Van de Sande
Status Final
Created 2016-01-14
Category ERC


In English, convert the address to hex, but if the ith digit is a letter (ie. it’s one of abcdef) print it in uppercase if the 4*ith bit of the hash of the lowercase hexadecimal address is 1 otherwise print it in lowercase.



  • Backwards compatible with many hex parsers that accept mixed case, allowing it to be easily introduced over time
  • Keeps the length at 40 characters
  • On average there will be 15 check bits per address, and the net probability that a randomly generated address if mistyped will accidentally pass a check is 0.0247%. This is a ~50x improvement over ICAP, but not as good as a 4-byte check code.
dido/public/ra/xapend/xapend.b_stds/defact/ethereum/eip/erc_0055.txt · Last modified: 2020/11/13 02:21 by nick
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