What is SHA-512 hashing algorithm?
SHA-512 is a hashing algorithm that performs a hashing function on some data given to it. Hashing algorithms are used in many things such as internet security, digital certificates and even blockchains and play a vital role in digital security and cryptography. It’s part of a group of hashing algorithms called SHA-2 which includes SHA-256 as well which is used in the bitcoin blockchain for hashing.
Hashing Functions
Hashing functions take some data as input and produce an output (called hash digest) of fixed length for that input data. This output should, however, satisfy some conditions to be useful.
- Uniform distribution: Since the length of the output hash digest is of a fixed length and the input size may vary, it is apparent that there are going to be some output values that can be obtained for different input values. Even though this is the case, the hash function should be such that for any input value, each possible output value should be equally likely. That is to say that every possible output has the same likelihood to be produced for any given input value.
- Fixed Length: This is should be quite self-explanatory. The output values should all be of a fixed length. So, for example, a hashing function could have an output size of 20 characters or 12 characters, etc. SHA-512 has an output size of 512 bits.
- Collision resistance: Simply speaking, this means that there aren’t any or rather it is not feasible to find two distinct inputs to the hash function that result in the same output (hash digest).
Hashing Algorithm — SHA-512
So, SHA-512 does its work in a few stages. These stages go as follows:
- Input formatting
- Hash buffer initialization
- Message Processing
- Output
Let’s look at these one-by-one.
1. Input Formatting:
SHA-512 can’t actually hash a message input of any size, i.e. it has an input size limit. This limit is imposed by its very structure as you may see further on. The entire formatted message has basically three parts: the original message, padding bits, size of original message. And this should all have a combined size of a whole multiple of 1024 bits. This is because the formatted message will be processed as blocks of 1024 bits each, so each bock should have 1024 bits to work with.
2. Hash buffer initialization:
The algorithm works in a way where it processes each block of 1024 bits from the message using the result from the previous block. Now, this poses a problem for the first 1024 bit block which can’t use the result from any previous processing. This problem can be solved by using a default value to be used for the first block in order to start off the process.
3. Message Processing:
Message processing is done upon the formatted input by taking one block of 1024 bits at a time. The actual processing takes place by using two things: The 1024 bit block, and the result from the previous processing.
4. Output:
After every block of 1024 bits goes through the message processing phase, i.e. the last iteration of the phase, we get the final 512 bit Hash value of our original message. So, the intermediate results are all used from each block for processing the next block. And when the final 1024 bit block has finished being processed, we have with us the final result of the SHA-512 algorithm for our original message.