信息技术.安全技术.电文鉴别代码(MACS).第2部分:专用散列函数的机械结构

[中文适用范围]： ISO/IEC 9797 的这一部分指定了三种 MAC 算法，它们使用密钥和具有 n 位结果的散列函数（或其轮函数）来计算 m 位 MAC。 这些机制可以用作数据完整性机制，以验证数据没有以未经授权的方式更改。 它们还可以用作消息认证机制，以确保消息是由拥有密钥的实体发起的。 数据完整性机制和消息认证机制的强度取决于密钥的长度（以位为单位）k和保密性、散列函数产生的散列码的长度（以位为单位）n、强度哈希函数、MAC 的长度（以位为单位）m 以及具体机制。 ISO/IEC 9797 本部分中指定的三种机制基于 ISO/IEC 10118-3 中指定的专用哈希函数。 ISO/IEC 9797 本部分规定的第一个机制通常称为 MDx-MAC。 它调用一次完整的哈希函数，但它通过向轮函数中的加性常量添加一个键来对轮函数进行小的修改。 ISO/IEC 9797 本部分中指定的第二种机制通常称为 HMAC。 它调用完整的哈希函数两次。 ISO/IEC 9797 这部分中指定的第三种机制是 MDx-MAC 的变体，它仅将短字符串（最多 256 位）作为输入。 它为仅使用短输入字符串的应用程序提供了更高的性能。 ISO/IEC 9797 的这一部分可应用于任何安全架构、流程或应用程序的安全服务。 [外文原描述]： ISO/IEC 9797-2:2002 specifies three MAC algorithms that use a secret key and a hash-function (or its round-function) with an n-bit result to calculate an m-bit MAC. These mechanisms can be used as data integrity mechanisms to verify that data has not been altered in an unauthorised manner. They can also be used as message authentication mechanisms to provide assurance that a message has been originated by an entity in possession of the secret key. The strength of the data integrity mechanism and message authentication mechanism is dependent on the length (in bits) k and secrecy of the key, on the length (in bits) n of a hash-code produced by the hash-function, on the strength of the hash-function, on the length (in bits) m of the MAC, and on the specific mechanism. The three mechanisms specified in ISO/IEC 9797-2:2002 are based on the dedicated hash-functions specified in ISO/IEC 10118-3. The first mechanism specified in ISO/IEC 9797-2:2002 is commonly known as MDx-MAC. It calls the complete hash-function once, but it makes a small modification to the round-function by adding a key to the additive constants in the round-function. The second mechanism specified in ISO/IEC 9797-2:2002 is commonly known as HMAC. It calls the complete hash-function twice. The third mechanism specified in ISO/IEC 9797-2:2002 is a variant of MDx-MAC that takes as input only short strings (at most 256 bits). It offers a higher performance for applications that work with short input strings only. ISO/IEC 9797-2:2002 can be applied to the security services of any security architecture, process, or application.