Using weil pairing

an identity-based ring signcryption scheme is proposed.Its concrete algorithm is given.Using this scheme the message sender can anonymously send the message

the confidentiality and authenticity of message are realized at the same time.It is proved that the scheme is secure against adaptively chosen cipher text attack under the difficulty of the Decisional Bilinear Diffie-Hellman problem.Compared with the traditional "signature then encryption scheme"

the cipher text of our scheme is rather short.So our scheme is more applicable to systems where cryptogram is sent over a low bandwidth channel.