Difference Between SHA1 and SHA2 (original) (raw)

Last Updated : 15 Jul, 2025

SHA is an important aspect of cryptographic algorithms as it guarantees integrity when it comes to information. SHA1 and SHA2 are the most commonly used hashing algorithms in security solutions, such as in SSL certificates and in digital signatures. Even though these two algorithms have almost the same name, there are stark differences between them in terms of security and performance and where can be applied. Relating between these two terminologies is important especially while selecting the most appropriate algorithm for data security.

SHA1 (Secure Hash Algorithm 1)

SHA1 is a cryptographic hash function which is designed by the United States National Security Agency. It takes an input and produces a 160-bit hash value. Further, the output produced by this function is converted into a 40-digit 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

Advantages of SHA1

Widely Used: SHA1 has been utilized in different applied fields for years that have elapsed.
**Compatibility: Due to the length of its use in many hosting structures, SHA1 is compatible with lots of legacy structures.

Disadvantages of SHA1

**Security Vulnerabilities: SHA1 has been viewed over the years as vulnerable to collision attacks whereby two different data sets yield the same hash.
**Deprecation: SHA1 has many weaknesses; therefore, it is no longer used for security-concerned applications, and has been replaced by more secure hashes.

**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

Advantages of SHA2

**Enhanced Security: SHA2 is much more secure than SHA1; no feasible collision attack has been identified on the later.
**Flexibility: SHA2 is not just a single algorithm, but contains numerous versions of the algorithm such as SHA-256, SHA-512 among others and this is due to the fact that each of the algorithms come with a different form of security and the ability to perform in a certain manner.
**Widespread Adoption: Owing to these specified attributes; SHA2 is used in the modern cryptographic applications including, SSL certificates and the blockchain technologies.

Disadvantages of SHA2

Performance Overhead: Despite these, SHA2 may take more time to compute than SHA1, which might be a limitation in environments where the use of resources is limited.
**Legacy System Compatibility: SHA2 might not be supported in some older systems and this might call for upgrades or new acquisition.

**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.

Conclusion

Although SHA1 was widely used in cryptographic security systems at one point, it has been replaced rather significantly by the SHA2 because of its shortcomings. SHA2 is more secure and flexible and hence is the most suitable choice in today’s developments. If traditional cryptographic practices are shifting, the decision of which type of algorithm is most suitable is based on the level of security required in opposition to the speed and compatibility of the computers and the protective programs in the network.