信息技术 安全技术 校验字符系统

[中文适用范围]： 1．1 本标准规定了一组校验字符系统，它可以防止在复制或键人数据时产生的串的错误。串的长度 可以是固定的或是可变的，包括以下字符集中的字符： a)数字(10个数字：O～9)； b) 字母(26个字母：A～Z)； c) 字母数字(字母和数字)。 串中嵌入的空格和特殊字符忽略不计。 1．2本标准为生成校验字符和校验串产品规约了一致性要求，这些产品采用了本标准所给出的系统。 1．3 这些校验字符系统能检查出下列错误： a) 所有的单一字符替换错误(即，单个字符被另一个字符所替换，如1234被错录为4234)； b)所有的或几乎所有的单一字符对换位置错误(即，相邻两个字符或隔一个字符的两个单一字 符的位置互换，如12345被错录为123 54或12 54 3)； c) 所有或几乎所有的循环移位错误(即，整个串被向左或向右循环移位)； d) 大部分的双替换错误(即，在同一串中，分开的两处单一字符替换错误，如1234567被错录为 72345 87)； e) 大部分的其他错误。 1．4本标准不包括专门为下列目的而设计的系统： a)既允许差错检测，又允许自动校正； b)检测故意误用； c) 仅校验在机器之间交换的串。 1．5本标准用于各组织之间的信息交换，极力推荐用于内部信息系统。 [外文原描述]： ISO/IEC 7064:2002 specifies a set of check character systems capable of protecting strings against errors which occur when people copy or key data. The strings may be of fixed or variable length and may have character sets which are numeric (10 digits: 0 to 9);alphabetic (26 letters: A to Z);alphanumeric (letters and digits). Embedded spaces and special characters are ignored. ISO/IEC 7064:2002 specifies conformance requirements for products described as generating check characters or checking strings using the systems given in this International Standard. ISO/IEC 7064:2002 is for use in information interchange between organizations; it is also strongly recommended as good practice for internal information systems. The check character systems specified in ISO/IEC 7064:2002 can detect: all single substitution errors (the substitution of a single character for another, for example 4234 for 1234);all or nearly all single (local) transposition errors (the transposition of two single characters, either adjacent or with one character between them, for example 12354 or 12543 for 12345);all or nearly all shift errors (shifts of the whole string to the left or right);a high proportion of double substitution errors (two separate single substitution errors in the same string, for example 7234587 for 1234567);a high proportion of all other errors. ISO/IEC 7064:2002 excludes systems designed specifically to: permit both error detection and automatic correction;detect deliberate falsification;check strings interchanged solely between machines. ISO/IEC 7064:2002 specifies two types of systems: pure systems;hybrid systems. The pure systems use a single modulus for all stages of the calculation.