SHA-2 vs. SHA-3

Attribute	SHA-2	SHA-3
Year of Introduction	2001	2015
Block Size	512 bits (SHA-224, SHA-256), 1024 bits (SHA-384, SHA-512)	1600 bits
Output Size	224 bits (SHA-224), 256 bits (SHA-256), 384 bits (SHA-384), 512 bits (SHA-512)	224 bits, 256 bits, 384 bits, 512 bits
Security	Considered secure	Considered secure
Algorithm	Merkle-Damgård construction	Sponge construction

Introduction

Secure Hash Algorithms (SHA) are cryptographic hash functions designed to generate a fixed-size hash value from input data. SHA-2 and SHA-3 are two popular members of the SHA family, each with its own set of attributes and characteristics. In this article, we will compare the attributes of SHA-2 and SHA-3 to understand their differences and similarities.

Algorithm Structure

SHA-2, which includes SHA-224, SHA-256, SHA-384, SHA-512, SHA-512/224, and SHA-512/256, is based on the Merkle-Damgård construction. It processes data in blocks of 512 bits and produces a hash value of fixed length. On the other hand, SHA-3, also known as Keccak, is based on the sponge construction. It operates on arbitrary-length input data and produces a hash value of variable length.

Security

SHA-2 has been widely used and studied for many years, making it a well-established and trusted cryptographic hash function. It is considered secure against known attacks, such as collision and pre-image attacks. SHA-3, on the other hand, was designed as a response to potential vulnerabilities in SHA-2. It offers a different approach to hashing and aims to provide improved security guarantees.

Performance

SHA-2 is known for its efficiency and speed in generating hash values. It is optimized for performance on a wide range of platforms and has been implemented in various software and hardware systems. SHA-3, on the other hand, may not be as widely supported as SHA-2 in terms of implementation and performance optimizations. However, it offers a different set of performance characteristics that may be beneficial in certain use cases.

Resistance to Attacks

SHA-2 has been subjected to extensive cryptanalysis over the years, and no significant vulnerabilities have been found that would compromise its security. It is considered resistant to various types of attacks, including collision attacks and pre-image attacks. SHA-3, being a relatively newer algorithm, has not undergone the same level of scrutiny as SHA-2. However, its design principles and the competition process that led to its selection provide confidence in its resistance to attacks.

Flexibility

SHA-2 offers a fixed output size for each of its variants, which may limit its flexibility in certain applications that require variable-length hash values. SHA-3, on the other hand, provides the flexibility to generate hash values of different lengths, making it suitable for a wider range of use cases. This flexibility can be advantageous in scenarios where the size of the hash value needs to be customized based on specific requirements.

Standardization

SHA-2 is a widely adopted and standardized hash function that is used in various security protocols and applications. It is supported by major cryptographic libraries and frameworks, making it a popular choice for implementing secure hashing. SHA-3, on the other hand, is a relatively newer algorithm that is gradually gaining acceptance and adoption in the industry. It has been standardized by NIST and is expected to see increased usage in the coming years.

Conclusion

In conclusion, SHA-2 and SHA-3 are two prominent members of the SHA family with distinct characteristics and attributes. While SHA-2 is a well-established and trusted hash function known for its security and performance, SHA-3 offers a different approach to hashing with potential advantages in flexibility and resistance to attacks. The choice between SHA-2 and SHA-3 depends on the specific requirements of the application and the level of security and performance needed.