**1. SHA1 (Secure Hash Algorithm 1) :**

SHA1 is a cryptographic hash function which is designed by United States National Security Agency. It takes an input and produces a 160 bits hash value. Further the output produced by this function is converted into a 40 digits long hexadecimal number. It is a U.S. Federal Information Processing Standard. It was first published in 1995. It is successor to SH0 published in 1993.

**Example:**

Data : Geeksforgeeks SHA1 : bc7623b7a94ed3d8feaffaf7580df3eca4f5f5ca

**2. SHA2 (Secure Hash Algorithm 2) :**

SHA1 is also a cryptographic hash function which is designed by United States National Security Agency. It is constructed using the Merkle-Damgard structure from a one-way compression function. The compression function used is constructed using the Davies-Meyer structure from a classified block cipher. It was first published in 2001. It is successor to SH1.

**Example:**

Data : Geeksforgeeks SHA2(256) : 86d755349c6b9f95f365c6ffe7734f25bf2b00cabe8c6bc5f2b8b746c1aac332

**Difference between SHA1 and SHA2 :**

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. |

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