qp-poseidon-core

A pure Rust implementation of the Poseidon hash function using plonky3 field arithmetic. This crate provides the core cryptographic functionality without any external dependencies beyond plonky3.

Features

• No-std compatible: Works in embedded and constrained environments
• Pure cryptography: No blockchain or external dependencies
• Circuit-compatible: Padding behavior matches zero-knowledge circuit implementations
• Field arithmetic: Built on battle-tested plonky3 Goldilocks field

Basic Usage

use qp_poseidon_core::PoseidonCore;

// Hash some bytes with padding (recommended for circuit compatibility)
let data = b"hello world";
let hash = PoseidonCore::hash_for_circuit(data);
println!("Hash: {:?}", hash);

// Hash without padding
let hash_no_pad = PoseidonCore::hash_no_pad_bytes(data);

Working with Field Elements

use qp_poseidon_core::{PoseidonCore, injective_bytes_to_felts};
use plonky3::field::goldilocks_field::GoldilocksField;

// Convert bytes to field elements
let data = b"test data";
let felts = injective_bytes_to_felts(data);

// Hash field elements directly
let hash = PoseidonCore::hash_padded_felts(felts);

Utility Functions

The crate provides several utility functions for converting between different data types and field elements:

use qp_poseidon_core::{u64_to_felts, u128_to_felts, injective_string_to_felts};

// Convert numbers to field elements
let num_felts = u64_to_felts(12345);
let large_num_felts = u128_to_felts(123456789012345);

// Convert strings to field elements (max 8 bytes)
let string_felts = injective_string_to_felts("hello");

Constants

• FIELD_ELEMENT_PREIMAGE_PADDING_LEN: usize = 160 - Minimum field elements for circuit-compatible padding

Padding Behavior

• Padded functions: Automatically pad input to FIELD_ELEMENT_PREIMAGE_PADDING_LEN field elements
• Unpadded functions: Hash input as-is without modification
• Field element conversion: Uses injective mapping to preserve input uniqueness

Performance

• Optimized for deterministic behavior across platforms
• Memory efficient for constrained environments
• Uses plonky3's optimized field arithmetic
• No heap allocations in core hashing (only in utility functions)

Security

• Built on battle-tested plonky3 field arithmetic
• Implements standard Poseidon permutation
• Circuit-compatible padding prevents length extension attacks
• Extensive test coverage with known test vectors

Related Crates

• qp-poseidon - Substrate-compatible wrapper around this core implementation
• plonky3 - The underlying field arithmetic and Poseidon implementation