rs_shake256

rs_shake256 is a Rust crate implementing the SHAKE256 Extendable-Output Function (XOF). This permutation-based function is designed for compatibility with Rust's libcore in a #![no_std] context, allowing it to operate as a standalone crate for specialized use cases and also function within a #![no_std], #![no_alloc] environment, rendering it suitable for systems where dynamic memory allocation is not feasible.

This implementation of SHAKE256 is compliant with the Federal Information Processing Standards (FIPS) Publication 202[^1]. As per the National Institute of Standards and Technology (NIST) guidelines, SHAKE256 is recommended for various use cases:

"SHAKE128 and SHAKE256 are extendable-output functions (XOFs), which can output a hash of variable length, are approved for all applications using hash functions that can benefit from variable-length output."

Given this advice, NIST recommendations imply that SHAKE256 is suitable for the following contexts:

• Digital signatures that require variable bits of security.
• Cryptographic hash functions in systems and protocols requiring variable bits of security.
• Authentication methods that necessitate variable bits of security.
• Applications where the output length is not fixed.

Beyond these specific recommendations, SHAKE256 could also find application in:

• Generation of unique identifiers in distributed systems[^2].
• Data integrity checks in Merkle Trees[^4].
• Hash-based message authentication codes (HMACs), when collision resistance is necessary[^3].
• Key derivation functions or in generation of random numbers[^6].

These points should be carefully considered, given your overall security objectives and risk tolerance.

For access to a comprehensive range of cryptographic functions, rs_shake256 can be utilized as part of the rs_shield library bundle.

How To Use

Below are steps to use the rs_shake256 crate in your Rust projects:

1. Add the following line to your Cargo.toml under the [dependencies] section:

   rs_shake256 = "0.1.*"
   

2. Use the functions provided by the rs_shake256 module in your code. Here's an example of how to create a SHAKE256 hash from a string:

   use rs_shake256::{HasherContext, Shake256Hasher};
   
   let mut sha512_256hasher = Shake256Hasher::<20>::default();
   sha512_256hasher.write(b"your string here");
   
   let u64result = sha512_256hasher.finish();
   let bytes_result = HasherContext::finish(&mut sha512_256hasher);
   assert_eq!(u64result, 0x97E1C052B5574F11);
   assert_eq!(format!("{bytes_result:02x}"), "97e1c052b5574f117b3fb13f26865fb4eec4a473");
   assert_eq!(format!("{bytes_result:02X}"), "97E1C052B5574F117B3FB13F26865FB4EEC4A473");
   assert_eq!(
       bytes_result,
       [
           0x97, 0xE1, 0xC0, 0x52, 0xB5, 0x57, 0x4F, 0x11, 0x7B, 0x3F, 0xB1, 0x3F, 0x26, 0x86, 0x5F, 0xB4, 0xEE, 0xC4,
           0xA4, 0x73
       ]
   )
   

More Information

For a more detailed exploration of rs_shake256, an overview of other available cryptographic functions, and an introduction to the broader rs_shield project, please consult the RustyShield project page on crates.io.

Contributions

Potential contributors are encouraged to consult the contribution guidelines on our GitHub page.

License

This project is licensed under GPL-2.0-only.

References

[^1]: National Institute of Standards and Technology. (2015). SHA-3 Standard: Permutation-Based Hash and Extendable-Output Functions. FIPS PUB 202

[^2]: Linus Torvalds. (2005). Git: A distributed version control system. Software: Practice and Experience, 41(1), 79-88. DOI:10.1002/spe.1006

[^3]: Krawczyk, H., Bellare, M., & Canetti, R. (1997). HMAC: Keyed-Hashing for Message Authentication. RFC 2104

[^4]: Merkle, R. C. (1988). A Digital Signature Based on a Conventional Encryption Function. Link

[^6]: National Institute of Standards and Technology. (2012). Recommendation for Key Derivation through Extraction-then-Expansion. SP 800-56C

Note: The references have been provided as per the best knowledge as of May 17, 2023.