yaSHAck256

This implementation is yet another 256-bit SHA hack for a subset of the specified secure hash algorithms, SHA-256, as described in the Secure Hash Standard, Ch. 4.1.2 of FIPS PUB 180-4.

Summary

Hash algorithms that can be used to generate digests of messages that are used to detect whether messages have been changed since the digests were generated.

This repository contains a Rust implementation of the SHA-256 secure hash algorithm.

The SHA-2 hash function is widely deployed in applications ranging from several cryptocurrencies to security protocols.

Main

If no arguments are given, one file of the repository ("tests/test_template.rs") is hashed for demonstrations purposes. If an arguments is given, it is assumed to be a file_to_hash whose content is then hashed. If this assumption does not hold, the hash values of an empty string, i.e., a zero-length input text, SHA256("") is computed and checked against 0xe3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855.

tl;dr

• cargo run tests/test_temp.rs uses "" for demo,
• cargo run tests/test_template.rs uses "tests/test_template.rs" for demo,
• cargo run uses "tests/test_template.rs" for demo.

Tests

A few unit tests cover the most obvious mistakes, run them very explicitly via:

cargo test --package yashack256 --bin yashack256 -- test_vectors --exact --nocapture

or simply:

cargo test --release -- test_vectors

Keywords

computer security, cryptographic algorithm, message digest, hash function, FIPS Secure Hash Standard.

Disclaimer

While SHA-256 is considered secure because, for a given algorithm, it is computationally infeasible to find

1. a pre-image, i.e., a message corresponding to a given digest, or
2. two different messages that produce a collision, i.e., the same message digest.

the implementation is not to be considered production-ready. Use at own risk.

Any change to a message will, with a very high probability, result in a different message digest. This will result in a verification failure when the secure hash algorithm is used with a digital signature algorithm or a keyed-hash message authentication algorithm.