Function find_solution 

pub fn find_solution(
    challenge: &IronShieldChallenge,
    config: Option<PoWConfig>,
    start_offset: Option<usize>,
    stride: Option<usize>,
    progress_callback: Option<&dyn Fn(u64)>,
) -> Result<IronShieldChallengeResponse, String>

Find a solution for the given IronShieldChallenge using optimized multithreaded computation.

Implements thread-stride approach delegated to multiple threads (e.g. Web Workers or Tokio tasks) for maximum performance. The lack of chunking of nonces between threads dramatically increases performance since threads don’t have to constantly communicate and distribute work. Each thread is mathematically guaranteed to not check overlapping nonces with other threads.

Algorithm:

1. Pre-computes the random_nonce bytes once to avoid repeated hex decoding
2. Assigns each thread a start_offset and stride
3. Each thread performs the single-threaded algorithm with a stride and offset
4. Returns immediately when a solution is found

Arguments

• challenge: The IronShieldChallenge struct containing random_nonce and challenge_param
• num_threads: Ignored (for compatibility only)
• start_offset: Starting nonce for this worker’s search range (JavaScript coordination)
• stride: Nonce increment step for thread-stride pattern (JavaScript coordination)

Returns

• Result<IronShieldChallengeResponse, String>: Ok(IronShieldChallengeResponse) that contains the successful nonce, or an error (Err(String)) message if no solution is found within config.max_attempts.

Example

use ironshield_core::{
    IronShieldChallenge,
    find_solution,
    SigningKey
};

    let dummy_key = SigningKey::from_bytes(&[0u8; 32]);
    let challenge = IronShieldChallenge::new(
        "website".to_string(),
        1,           // difficulty
        dummy_key,
        [0x00; 32],  // public_key
     );

    // JavaScript worker coordination mode
    let response = find_solution(&challenge, None, Some(0), Some(8), None)?;
    println!("Found solution: {}", response.solution);