摘要： 由标准哈希算法SHA-2 演变而来的SHACAL-2 是新当选的3 个欧洲分组密码标准算法中分组长度和密钥长度最长的算法，其安全强度被认为最高。提案沿袭单向哈希函数的形式来描述算法，文章以分组密码传统的规范形式刻画SHACAL-2 算法的完整加密过程，指出算法扩散特性较差的缺点，给出分组密码算法加密过程与哈希算法压缩过程的对应关系，并提供了算法的详细解密过程和相应的加解密数据，为算法实现提供参照：补充了相应的轮常数；进一步研究了长分组长度和密钥长度的必要性，指出算法加解密结构不具有相似性。最后，对欧美4 个分组密码标准进行了比较分析。

关键词: NESSIE 计划；分组密码；SHACAL-2；哈希函数

Abstract: The SHACAL-2 algorithm based on the standard hash algorithm SHA-2 has the longest block length and biggest key size among the three standard block ciphers selected by NESSIE and it is viewed as the strongest cipher. But the specification has described only the encryption procedure of the algorithm, like the one-way property of its underlying hash function. A description of SHACAL-2 encryption and decryption in a conventional and formal manner is proposed, as well as the round constants. Four rounds of encryption data are provided as implementation test data. The poor diffusion of the algorithm is pointed out and the relationship between block cipher and the hash function is depicted. It also discusses the necessity of long block length and large key size and paid attention to the lack of similarity of encryption and decryption procedures. A comparison of the three standard block ciphers of NESSIE and AES is provided in the end

Key words: NESSIE project; Block cipher; SHACAL-2; Hash function