I have a 256-bit private key and I want to get its public address without having to install Geth (which is quite heavy) on the machine. Is there any small JS lib that does that?


You want lightweight and Javascript... how's this? https://github.com/ethereumjs/ethereumjs-util

npm install ethereumjs-util


var ethUtils = require('ethereumjs-util')
var privateKey = new Buffer([234, 84, 189, 197, 45, 22, 63, 136, 201, 58, 176, 97, 87, 130, 207, 113, 138, 46, 251, 158, 81, 167, 152, 154, 171, 27, 8, 6, 126, 156, 28, 95])
var address = ethUtils.privateToAddress(privateKey).toString('hex')
// address will be 2f015c60e0be116b1f0cd534704db9c92118fb6a

If you have the private key in hex, then you can the use Buffer constructor with second argument as 'hex', example:

var privateKey = new Buffer('ea54bdc52d163f88c93ab0615782cf718a2efb9e51a7989aab1b08067e9c1c5f', 'hex')

It has few more utility functions than you asked for, but you will need at least a crypto library (and in turn a bignumber library).

  • Hmm not so awesome. That file seems to depend on installing C libraries (wtf?) that do not install at all. I need something browser compatible... could you browserify the relevant parts? – MaiaVictor Feb 6 '16 at 13:39
  • ethereumjs-accounts may help, but it will be heavier. – eth Feb 7 '16 at 0:23
  • ethereumjs-tx may actually be a middle-ground you are looking for, browser compatible and lighter than ethereumjs-accounts. – eth Feb 7 '16 at 0:27
  • I'm not sure how that helps, I'm supposed to create a fake transaction and get the public address of the private key from it? :| – MaiaVictor Feb 7 '16 at 17:31
  • ethereumjs-tx says it creates an ethUtil global, so should be able to use privateToAddress like answer. – eth Feb 8 '16 at 5:48

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