const { randomBytes } = require('crypto')

const IVLENGTHS = {
  'A128CBC-HS256': 128 / 8,
  A128GCM: 96 / 8,
  A128GCMKW: 96 / 8,
  'A192CBC-HS384': 128 / 8,
  A192GCM: 96 / 8,
  A192GCMKW: 96 / 8,
  'A256CBC-HS512': 128 / 8,
  A256GCM: 96 / 8,
  A256GCMKW: 96 / 8
}

module.exports = alg => randomBytes(IVLENGTHS[alg])