Perfect ciphers have been a very attractive cryptographic tool ever since C. Shannon described them. Note that, by definition, if a perfect cipher is used, no one can get any information about the encrypted message without knowing the secret key. We consider the problem of reducing the key length of perfect ciphers, because in many applications the length of the secret key is a crucial parameter. This paper describes a simple method of key length reduction. This method gives a perfect cipher and is based on the use of data compression and randomisation, and the average key length can be made close to Shannon entropy (which is the key length limit). It should be noted that the method can effectively use readily available data compressors (archivers).

翻译：完美密码自香农（C. Shannon）提出以来，一直是一种极具吸引力的密码学工具。注意，根据定义，若使用完美密码，任何人在不知晓密钥的情况下都无法获取关于加密消息的任何信息。我们考虑缩短完美密码密钥长度的问题，因为在众多应用中，密钥长度是关键参数。本文描述一种简单的密钥长度缩减方法。该方法基于数据压缩与随机化的结合，能够实现完美密码，且平均密钥长度可接近香农熵（即密钥长度极限）。需要指出的是，该方法可有效利用现成的数据压缩器（归档工具）。