利用射影几何构作一类完备的A~2—码

利用射影几何构作一类完备的带仲裁的认证码,计算了码的参数及各种攻击成功的概率。     

利用酉几何构作新的Cartesian认证码(Ⅰ)

利用有限域上酉几何构作一类新的Cartesian认证码,计算了码的参数。当编码规则按等概率分布选取时,计算出敌方成功的模仿攻击概率和成功的替换攻击概率。     

利用酉几何构作新的Cartesian认证码(Ⅱ)

利用有限域上酉几何构作了两类Cartesian认证码,计算了这些码的参数．当编码规则按等概率分布选取时,计算出敌方成功的模仿攻击概率和成功的替换攻击概率．     

利用辛几何构作带仲裁的认证码

本文利用辛几何构作一类带仲裁的认证码,计算了码的参数;当编码规则按等概率分布选取时,计算出各种攻击成功的概率并在特殊情况下得到一组完备码。     

基于区组设计的具有仲裁的无条件安全认证码的构造

本文借助区组设计给出一类具有仲裁的无条件安全认证码的构造方法,并给出一种安全的无条件安全认证码的构造方法,计算了有关参数。     

基于分组可裂设计的分裂认证码的构造

分裂认证码是研究带仲裁的认证码的一种重要手段,相对无分裂认证码而言,分裂认证码大大提高了编码规则的利用率,该文主要通过可分组设计构造分裂认证码.首先给出了通过可分组设计(GDD)构造分裂认证码的定理,利用可分组设计构造可裂可分组设计,再由可裂可分组设计构造可裂平衡不完全区组设计(BIBD),进而得到分裂认证码;验证在该...     

基于区组设计的具有仲裁的无条件安全认证码的构造

本文借助区组设计给出一类具有仲裁的无条件安全认证码的构造方法,并给出了一种安全的无条件安全认证码的构造方法,计算了有关参数。     

利用垂直阵列构作Cartesian认证码

利用垂直阵列构作了一类Cartesian认证码,计算了它们的参数,并且在编码规则按等概率分布选取时,成功的模仿攻击和成功的替换攻击概率也被算出。     

完备的具有仲裁的认证码的组合特征

具有仲裁的认证码既要防止发方和收方的互相期骗,又要防止敌手的欺骗,本文安全刻划了完备的具有仲裁的认证码的组合特征。     

由分裂认证码构造有仲裁认证码

本文利用t分裂认证码构造了一类有仲裁认证码(A~2码),并对给出的A~2码中各种攻击成功的概率进行了研究。     

Rotationally Invariant Convolutional Channel Coding with Expanded Signal Space--Part I:180°

Convolutional channel coding with expanded signal space improves error performance of synchronous data links without sacrificing data rate or requiring more bandwidth. Due to the phase ambiguity(ies) in the expanded signal space, it is desirable to design the code' to be transparent to signal element rotations. In this paper, design rules and procedures for 180° rotationally invariant codes are presented. In a companion paper, we extend these rules and procedures to codes which are transparent to 90, 180, and 270° signal element rotations. We illustrate these rules and procedures by designing simple codes that achieve coding gain of 3-4 dB. These are the codes of practical interest. Codes with higher coding gain can be obtained using the same rules and procedures. Both feedforward and feedback codes are considered.     

Rotationally Invariant Convolutional Channel Coding with Expanded Signal Space--Part II: Nonlinear Codes

This is the second paper on rotationally invariant convolutional channel coding with expanded signal space. Signal space with 90, 180, and 270° phase ambiguities is generally preferred to signal space with only 180° phase ambiguity. In this paper, design rules and procedures for 180° rotationally invariant convolutional codes in the previous paper are extended to rotationally invariant codes with expanded signal space having 90, 180, and 270° phase ambiguities. As in the previous paper, we illustrate these rules and procedures by designing simple codes with coding gain of 4 dB. Nonlinear convolutional codes result from these design rules and procedures. These simple nonlinear convolutional codes are being considered as international standards on voiceband modems at rate greater than or equal to 9.6 kbits/s. Codes with higher coding gain can be obtained using the same rules and procedures. Both feedforward and feedback codes are considered. In addition, a new class of codes described as "generalized feedback" is also considered.     

On a technique to calculate the exact performance of aconvolutional code

A Markovian technique is described to calculate the exact performance of the Viterbi algorithm used as either a channel decoder or a source encoder for a convolutional code. The probability of information bit error and the expected Hamming distortion are computed for codes of various rates and constraint lengths. The concept of tie-breaking rules is introduced and its influence on decoder performance is examined. Computer simulation is used to verify the accuracy of the results. Finally, we discuss the issue of when a coded system outperforms an uncoded system in light of the new results     

Error-propagation properties of uniform codes

The problem of error propagation in uniform codes is investigated using the concept of parity-parallelogram submatrices and the threshold-decoding algorithm. A set of optimum orthogonalization rules is presented and it is shown that if these rules are incorporated into the decoder, then sufficient conditions can be found for the return of the decoder to correct operation following a decoding error. These conditions are considerably less stringent than the requirement that the channel be completely free of errors following a decoding error. However, this is not the case if the prescribed orthogonalization rules are not followed, as is demonstrated with a simple example. It is also shown that the syndrome memory required with Massey's orthogonalization procedure for definite decoding of uniform codes is the lowest possible. The results of simulation of the ratefrac{1}{4}andfrac{1}{8}uniform codes are presented, and these codes are seen to make fewer decoding errors with feedback decoding than with definite decoding. Comparison of the performance of an ordinary feedback decoder with a genie-aided feedback decoder, which never propagates errors, indicates that error propagation with uniform codes is a minor problem if the optimum orthogonalization rules are used, but that the situation is somewhat worse with nonoptimum orthogonalization.     

Realisation of a decoder for two MFM codes

The realisation of a decoder for two MFM codes, Miller and Jordan codes, enabling the decoding of both the quoted codes is presented. Also, the coding rules for these two codes are introduced through an auxiliary sequence of transitions.     

Complexity of decoders--I: Classes of decoding rules

Several classes of decoding rules are considered here including block decoding rules, tree decoding rules, and bounded-distance and minimum-distance decoding rules for binary parity-check codes. Under the assumption that these rules are implemented with combinational circuits and sequential machines constructed with AND gates, OR gates, INVERTERS, and binary memory cells, bounds are derived on their complexity. Complexity is measured by the number of logic elements and memory cells, and it is shown that minimum-distance and other decoders for parity-check codes can be realized with complexity proportional to the square of block length, although at the possible expense of a large decoding time. We examine tradeoffs between probability of error and complexity for the several classes of rules.     

关于CARTESIAN认证码的构造

本文用初等方法构造了几类使对手模仿和替换攻击成功的概率都达到最小,且编码规则数也达到最小的认证码;同时也构造了使对手模仿和替换攻击成功的概率都达到最小,且编码规则也达到最小,源状态数达到最多的最佳认证码。并给出一种在不增加编码规则数量的情况下,将Ｃａｒｔｅｓｉａｎ认证码改造成完备安全（Ｐｅｒｆｅｃｔ ｓｅｃｒｅｃｙ）认证码的方法。