增强安全性的LT码编译码方案

对LT码的编码方式进行修改，不产生度为1的数据包，改为产生相关联的度2和度3的编码数据包，避免信息的直接泄露. 由于不能使用常规的置信传播（BP）算法进行译码，相应给出在BP译码算法基础上增加度2数据包处理环节的译码算法（D2BP算法），同时也给出降低译码复杂度的高斯消元译码算法（SGE算法）. 仿真结果显示，D2BP算法可在较低的译码开销下成功完成删除度1的LT码的译码. SGE译码算法译码开销明显低于BP类的译码算法，信道删除概率对其译码性能没有影响. 相比较传统的高斯消元算法，SGE算法的复杂度明显下降.

Encoding and Decoding Scheme of Security-Enhanced LT Codes

There are a large number of LT encoded packets with degree one which are copies of source information packets. An illegal recipient can intercept the information with part of the encoded packets e-ven if the way of encoding is unknown. For this,the way of encoding of LT was modified. The packets with degree one is replaced with a pair packet of degree two and three. As the conventional BP algorithm can not decode this kind of codes, a BP-based decoding algorithm (D2BP) in which an extra processing for degree two packets is included was presented, while a complexity reduced Gaussian elimination deco-ding algorithm (SGE) is given. Simulations show that D2BP and SGE algorithms can successfully decode LT codes so that the degree one packets is deleted, and SGE algorithm has significantly higher decoding efficiency than BP and D2BP algorithms. The channel erasure has no influence on the decoding perform-ance of SGE. Compared with traditional Gauss elimination algorithm, the complexity of SGE algorithm is obviously decreased.