The ALTCHA Ruby Library is a lightweight, zero-dependency library designed for creating and verifying ALTCHA challenges.

This library is compatible with:

• Ruby 2.7+

• Demo server

To install the ALTCHA Ruby Library, add it to your Gemfile:

gem 'altcha'

Then run:

bundle install

Alternatively, install it directly using:

gem install altcha

Here’s a basic example of how to use the ALTCHA Ruby Library:

require 'altcha'

hmac_key = 'secret hmac key'

# Create a new challenge
options = Altcha::ChallengeOptions.new(
  hmac_key: hmac_key,
  max_number: 100000 # the maximum random number
)

challenge = Altcha.create_challenge(options)

# Example payload to verify
payload = {
  algorithm: challenge.algorithm,
  challenge: challenge.challenge,
  number: 12345, # Example number
  salt: challenge.salt,
  signature: challenge.signature
}

# Verify the solution
valid = Altcha.verify_solution(payload, hmac_key, true)
puts valid ? "Solution verified!" : "Invalid solution."

Creates a new challenge for ALTCHA.

Parameters:

• options [ChallengeOptions]:
  • algorithm [String]: Hashing algorithm to use (SHA-1, SHA-256, SHA-512, default: SHA-256).
  • max_number [Integer]: Maximum number for the random number generator (default: 1,000,000).
  • salt_length [Integer]: Length of the random salt (default: 12 bytes).
  • hmac_key [String]: Required HMAC key.
  • salt [String]: Optional salt string. If not provided, a random salt will be generated.
  • number [Integer]: Optional specific number to use. If not provided, a random number will be generated.
  • expires [Time]: Optional expiration time for the challenge.
  • params [Hash]: Optional URL-encoded query parameters.

Returns: Challenge

Verifies an ALTCHA solution.

Parameters:

• payload [Hash]: The solution payload to verify.
• hmac_key [String]: The HMAC key used for verification.
• check_expires [Boolean]: Whether to check if the challenge has expired.

Returns: Boolean

Extracts URL parameters from the payload's salt.

Parameters:

• payload [Hash]: The payload containing the salt.

Returns: Hash

Verifies the hash of form fields.

Parameters:

• form_data [Hash]: The form data to hash.
• fields [Array<String>]: The fields to include in the hash.
• fields_hash [String]: The expected hash value.
• algorithm [String]: Hashing algorithm (SHA-1, SHA-256, SHA-512).

Returns: Boolean

Verifies the server's signature.

Parameters:

• payload [String, ServerSignaturePayload]: The payload to verify (string or ServerSignaturePayload).
• hmac_key [String]: The HMAC key used for verification.

Returns: [Boolean, ServerSignatureVerificationData]

Finds a solution to the given challenge.

Parameters:

• challenge [String]: The challenge hash.
• salt [String]: The challenge salt.
• algorithm [String]: Hashing algorithm (SHA-1, SHA-256, SHA-512).
• max [Integer]: Maximum number to iterate to.
• start [Integer]: Starting number.

Returns: Solution, nil

MIT