Shamir's Secret Sharing Online

Shamir’s Secret Sharing is a cryptographic technique invented by Adi Shamir in 1979. It allows a secret (password, private key, seed phrase, etc.) to be split into multiple parts called shares.

This tool provides a fully functional implementation of Shamir’s Secret Sharing. The implementation uses finite field arithmetic and polynomial interpolation exactly as specified by Shamir’s original scheme. You can find the implementation details here.

We do not store, log any key you enter. This tool is intended for personal and educational use. We suggest not to use online tools to protect real production secrets.

Tool Documentation and Usage

Using this scheme, you can specify:

• Number of Shares (N) – Total shares to be generated
• Threshold (K) – Minimum number of shares needed to reconstruct the secret

Even if someone gets fewer than K shares, the secret cannot be recovered mathematically.

This makes SSS perfect for:

• Splitting crypto wallet keys
• Storing passwords securely
• Enterprise access control
• Multi-person authorization

2. Explanation of All Fields in the Form

🔹 Secret

This is the actual sensitive value you want to split. You can enter text, numbers, hex strings, binary, or encoded values depending on the selected mode.

🔹 Mode (UTF-8 / HEX / Binary)

Determines how the secret is interpreted and validated.

• UTF-8: Normal text input (passwords, phrases, etc.)
• HEX: Must be a valid hexadecimal string (0-9, A-F)
• Binary: Must contain only 0 and 1 characters

🔹 Number of Shares (N)

Total number of shares you wish to generate. Example: If N = 5, the tool will produce 5 independent shares.

🔹 Threshold (K)

Minimum shares required to rebuild the secret. If K = 3, any 3 of the total shares can recover the secret.

🔹 Share Outputs

After generation, each share contains two components:

• Index (X) – Position of the share
• Value (Y) – Computed polynomial output

Example share structure:

[1-fd34aa01], [2-09bc9932], ...

4. How to Read & Understand Generated Shares

Each share is unique, and no single share reveals anything about the secret. A typical generated share looks like this:

Share #1 → 1-8caff120934bd99a

Structure:

• 1 → X coordinate (share index)
• 8caff120934bd99a → Y value (polynomial output)

When K shares are combined, polynomial interpolation is performed to find:

S = f(0)

This tool performs the official Shamir’s Secret Sharing computation using:

• Finite field arithmetic (GF(256) or GF(2^8)) depending on mode
• Random polynomial generation:

  f(x) = S + a1x + a2x² + ... + a(k-1)x^(k-1)

• Evaluation of polynomial at x = 1...N
• Secure random coefficient generation
• Reconstruction using Lagrange interpolation

5. Advantages & Disadvantages

Advantages

• Mathematically secure – fewer than K shares reveal nothing
• Improves safety of passwords, crypto keys, and sensitive secrets
• Shares can be distributed among trusted people
• Simple, fast, and industry-approved cryptographic scheme

Disadvantages

• If all K threshold members lose their shares, the secret is unrecoverable
• Shares must be stored safely to avoid tampering
• Not suitable for extremely large secrets without encoding

Real-World Use Cases

• Splitting a crypto wallet private key among 3–5 people
• Storing an API key securely across multiple teams
• Multi-party recovery of master passwords
• Offline secure backup for seed phrases

7. Frequently Asked Questions (FAQ)

References

• Shamir’s secret sharing Wiki
• What Is Shamir’s Secret Sharing
• Shamir’s Secret Sharing for common people
• Explanation and Visualization