function rsaSign (input, algorithm, privateSecret) {
  try {
    // sign with rsa_private_key.pem
    return crypto.createSign(algorithm).update(input).sign(privateSecret, 'base64')
  } catch (e) {
    throw new Error(errorMap['003'].message)
  }
}
function rsaSign (input, algorithm, privateSecret) {
  try {
    
    return crypto.createSign(algorithm).update(input).sign(privateSecret, 'base64')
  } catch (e) {
    throw new Error(errorMap['003'].message)
  }
}
function rsaSign ( input , algorithm , privateSecret ) { try { // sign with rsa_private_key.pem return crypto . createSign ( algorithm ) . update ( input ) . sign ( privateSecret , 'base64' ) } catch ( e ) { throw new Error ( errorMap [ '003' ] . message ) } }
rsa sign
@param  {String} input             rsa sign input
@param  {String} algorithm         rsa sign algorithm
@param  {String} privateSecret     rsa sign secret
@return {String}                   rsa signature
rsa sign