function stronghash(entity) {
  if (entity.length === 0) {
    // fast-path empty
    return '1B2M2Y8AsgTpgAmY7PhCfg=='
  }

  return crypto
    .createHash('md5')
    .update(entity, 'utf8')
    .digest('base64')
}
Generate a strong hash.

@param {Buffer} entity
@return {String}
@api private