1. SHA1(安全哈希算法 1)：
SHA1 是由美国国家安全局设计的加密哈希函数。它接受一个输入并产生一个 160 位的哈希值。此外，此函数产生的输出被转换为 40 位长的十六进制数。它是美国联邦信息处理标准。它于 1995 年首次发布。它是 1993 年发布的 SH0 的继任者。
例子：
Data : Geeksforgeeks
SHA1 : bc7623b7a94ed3d8feaffaf7580df3eca4f5f5ca 2. SHA2(安全哈希算法 2)：
SHA1 也是美国国家安全局设计的加密哈希函数。它是使用 Merkle-Damgard 结构从单向压缩函数构建的。使用的压缩函数是使用 Davies-Meyer 结构从分类分组密码构建的。它于 2001 年首次发布。它是 SH1 的继任者。
例子：
Data : Geeksforgeeks
SHA2(256) : 86d755349c6b9f95f365c6ffe7734f25bf2b00cabe8c6bc5f2b8b746c1aac332 SHA1 和 SHA2 的区别：
| SHA1 | SHA2 |
|---|---|
| It is a cryptographic hash function designed by U.S National Security Agency to replace SH0. | It is a cryptographic hash function designed by U.S National Security Agency to replace SH1. |
| It was published in 1995. | While it was published in 2001. |
| It produces 160 bits hash value. | It produces 224, 256, 384 or 512 bits hash value. |
| It is successor to SH0 and predecessor to SH2. | It is successor to SH1 and predecessor to SH3. |
| It is less secure. | While it is more secure. |
| Its structure is based on Merkle–Damgard construction. | Its structure is based on Merkle–Damgard structure with Davies–Meyer compression function. |
| SHA1 certificates are not reliable. | SHA2 has more improved certificates. |
| It generates smaller hash. | While it generates larger hash. |
| Hash generated by SHA1 is weak. | While hash generated by SHA2 is strong. |
| It is not widely used now-a-days. | While it is used widely. |