哈希算法将任意长度的二进制值映射为固定长度的较小二进制值，这个小的二进制值称为哈希值。哈希值是一段数据唯一且极其紧凑的数值表示形式。如果散列一段明文而且哪怕只更改该段落的一个字母，随后的哈希都将产生不同的值。要找到散列为同一个值的两个不同的输入，在计算上是不可能的，所以数据的哈希值可以检验数据的完整性。-The hash algorithm to map arbitrary length binary value for the smaller binary value of the fixed-length, this small binary value called a hash value. The hash value is unique and extremely compact numerical representation of a piece of data. If the hash a plaintext and even if only to change the letter of the paragraph, followed by the hash will have different values. To find two different input hash for the same value, in the calculation is impossible, so the hash value of the data to test the integrity of the data.