Shamir

A Crystal implementation of Shamir's Secret Sharing algorithm.

Split a secret into n shares where any k shares can reconstruct the original secret, but k-1 shares reveal nothing.

Installation

Add this to your application's shard.yml:

dependencies:
  shamir:
    github: seanyeh/shamir.cr

Usage

Basic Example

require "shamir"

# Split a secret into 5 shares, requiring 3 to reconstruct
secret = "my secret message"
shares = Shamir.split(secret, 5, 3)

# Reconstruct the secret from any 3 shares
reconstructed = Shamir.combine(shares[0..2])
puts String.new(reconstructed)  # => "my secret message"

Shares can be serialized to hex strings for storage or transmission:

# Serialize shares to hex
shares = Shamir.split("my secret", 5, 3)
hex_strings = shares.map(&.to_hex)
# => ["01:a3f2e5d4...", "02:b8c3d9f1...", ...]

# Deserialize from hex
loaded_shares = hex_strings.map { |hex| Shamir::Share.from_hex(hex) }
secret = Shamir.combine(loaded_shares[0..2])

Limitations

• Maximum secret size: 65 bytes
• Maximum shares: 255

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

License

MIT