中文摘要：

针对现有的基于属性的签密方案密文长度会随属性数量的增长而增长导致通信量低下的问题，提出了一个常量密丈基于属性的门限签密方案。签密者（发送方）签密一段消息给解签密者（接收方）；接收方能成功解密当且仅当接收方的属性集合与发送方所用的加密属性集合的交集元素的个数大于k，接收方能确定签名是来自发送方当且仅当发送方的属性集合和发送方签名属性集合的交集元素的个数大于t，其中k、t都是门限值。该方案结合了基于属性的加密和签名，并提供了保密性、真实性、不可伪造和抗合谋攻击。与现有的方案相比，该方案实现了常量密文，具有更好的效率。

英文摘要：

Aiming at the problem of the low communication traffic of current attribute-based signcryption because the cipher- text length is linear with the number of attributes, this paper proposed an attribute-based threshold signcryption scheme with constant ciphertexts. With this technique, signcrypter（sender） used his own attribute set on behave of a member of signature attributes set to sign and used encryption attribute set to sign. The designcrypter （reciever） with specified attributes could designcrypt the ciphertext iff the number of the overlap between his own attributes set and encryption attribute set was more than k. The designcrypter was sure that the signcrypted message by the sender iff the number of the overlap between sender＇ s attributes set and signature attributes set was more than t ,where k and t were the threshold values. It combined attribute-based encryption and attribute-based signature, and provided collusion resistance, confidentiality, authenticity and unforgeability. In addition,this scheme achieves constant ciphertexts,which has better efficiency than Hu et al. ＇ s scheme.