eccrypto-scripts/bin/derive

#!/usr/bin/env node

'use strict'

var eccrypto = require('eccrypto')

var command = process.argv[0]
var script = process.argv[1]
var private_key  = process.argv[2]
var public_key = process.argv[3]

if (!(private_key && public_key)) {
  return process.stdout.write(JSON.stringify({
    error: 'private key or public key not given'
  }), function() {
    process.exit(1)
  })
}

var pka, pkb

try {
  pka = Buffer(private_key, 'hex')
  pkb = Buffer(public_key, 'hex')
} catch (err) {
  return process.stdout.write(JSON.stringify({
    error: 'public key, message or signature is not a hexadecimal string'
  }), function() {
    process.exit(1)
  })
}

eccrypto.derive(pka, pkb).then(function(shared_secret) {
  process.stdout.write(JSON.stringify({
    shared_secret: shared_secret.toString('hex')
  }), function() {
    process.exit(0)
  })
}).catch(function(err) {
  process.stdout.write(JSON.stringify({
    eccrypto_error: JSON.stringify(err || true)
  }), function() {
    process.exit(1)
  })
})