Class: SolanaRuby::Ed25519CurveChecker

Inherits:
Object
  • Object
show all
Defined in:
lib/solana_ruby/ed25519_curve_checker.rb

Constant Summary collapse

Q =

Constants for the Ed25519 curve

2**255 - 19
D =

Ed25519 constant

-121665 * OpenSSL::BN.new(121666).mod_inverse(Q).to_i % Q

Class Method Summary collapse

Class Method Details

.on_curve?(public_key) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/solana_ruby/ed25519_curve_checker.rb', line 10

def self.on_curve?(public_key)
  return false unless public_key.bytesize == 32  # Must be exactly 32 bytes

  # Extract y-coordinate from the public key
  y = public_key.unpack1("H*").to_i(16) % Q

  # Compute x² from the Ed25519 curve equation: x² = (y² - 1) / (d * y² + 1) mod Q
  numerator   = (y**2 - 1) % Q
  denominator = (D * y**2 + 1) % Q

  # Compute the modular inverse of the denominator
  denominator_inv = OpenSSL::BN.new(denominator).mod_inverse(Q).to_i rescue nil
  return false if denominator_inv.nil?  # If inverse doesn't exist, it's off-curve

  x_squared = (numerator * denominator_inv) % Q

  # Check if x² is a quadratic residue (i.e., has a valid square root mod Q)
  legendre_symbol = OpenSSL::BN.new(x_squared).mod_exp((Q - 1) / 2, Q).to_i

  # If legendre symbol is 1, it has a square root, meaning it's ON the curve
  legendre_symbol == 1
rescue StandardError => e
  puts "Curve check error: #{e.message}"
  false
end