Overview of the cryptographic hash functions supported by OpenSSL

In this section, we will review the cryptographic hash functions supported by OpenSSL and their properties, such as security, speed, and message digest size. We will also learn a bit about the history of those hash functions.

Reviewing the SHA-2 family of hash functions

The SHA-2 family contains the most popular modern cryptographic hash function, SHA-256. SHA-256 outputs a 256-bit digest and has a collision resistance level of 128 bits.

SHA-256 is widely used. It is currently the default hash function that’s used in the TLS protocol, as well as the default signing function for X.509 certificates and SSH keys. Several cryptocurrencies, including Bitcoin, use SHA-256 to verify transactions and proof of work. The popular Git SCM is migrating to SHA-256 hashes for its blockchain implementation and object identification processes. SHA-256 is used in many security protocols and software, such as SSH, IPsec...