Abstract: In everyday life many documents require authorization from more than one party. For instance contracts, decisions and workflow systems etc. The purpose and use of multiple signatures are various. Multiple signature schemes realize that plural users generate the signature on a message and that the signature is verified. There is many multiple signature protocols available which satisfy order verifiability but not order flexibility and a message requiring N signatures would be increased in length by about N times as much as for one signature which is not feasible in economic perspective. An existing scheme does not provide security from unauthenticated message. In this study we propose a new multiple signature method with the following features. Multiple signatures with the same length as a single one. Multiplesigncrypt: Enhancing security by combining multiple signatures with encrypted data. Robust: Preventing unauthenticated users from attacking the text. Order Flexibility: Allowing the order of signers to be random. We have shown a RSA-based multisignature scheme which satisfies the above mentioned features.