Message Digests are secure, one-way hash functions that convert arbitrary length data into fixed-length check sum / hash code.

消息摘要是一个安全的、单向的哈希函数，把任意长度的数据转化成固定长度的校验和/哈希码。

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For a message digest, the strength of the algorithm is determined by the size of the hash or check sum that the algorithm generates.

对于消息摘要，算法的长度由算法生成的哈希码或者校验和决定。

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