A prefix code, a P-code, is a code where no codeword is a prefix of another codeword. In this paper, a symmetric cipher based on prefix codes is proposed. The simplicity of the design makes this cipher usable for Internet of Things applications. Our goal is to investigate the security of this cipher. A detailed analysis of the fundamental properties of P-codes shows that the keyspace of the cipher is too large to mount a brute-force attack. Specifically, in this regard we will find bounds on the number of minimal P-codes containing a binary word given in advance. Furthermore, the statistical attack is difficult to mount on such cryptosystem due to the attacker’s lack of information about the actual words used in the substitution mapping. The results of a statistical analysis of possible keys are also presented. It turns out that the distribution of the number of minimal P-codes over all binary words of a fixed length is Gaussian.

中文翻译：

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基于前缀码的密码

前缀码，P-码，是没有码字是另一个码字的前缀的码。本文提出了一种基于前缀码的对称密码。设计的简单性使该密码可用于物联网应用。我们的目标是调查这种密码的安全性。对P码基本属性的详细分析表明，密码的密钥空间太大，无法进行蛮力攻击。具体来说，在这方面，我们将找到最小P的数量的界限- 包含预先给出的二进制字的代码。此外，由于攻击者缺乏有关替换映射中使用的实际单词的信息，因此很难在这种密码系统上进行统计攻击。还提供了可能键的统计分析结果。事实证明，在所有固定长度的二进制字上的最小P码数量的分布是高斯分布的。