x25519.rb in x25519-1.0.2

- old
+ new

@@ -17,23 +17,26 @@
   module_function
 
   # Size of an X25519 key (public or private) in bytes
   KEY_SIZE = 32
 
+  # Raised when the built-in self-test fails
+  SelfTestFailure = Class.new(StandardError)
+
+  class << self
+    # Obtain the backend provider module
+    attr_accessor :provider
+  end
+
   # ref10 is the default provider
-  @provider = X25519::Provider::Ref10
+  self.provider = X25519::Provider::Ref10
 
   # X25519::Precomputed requires a 4th generation Intel Core CPU or newer,
   # so only enable it if we detect we're on a supported platform. Otherwise,
   # fall back to the ref10 portable C implementation.
-  @provider = X25519::Provider::Precomputed if X25519::Provider::Precomputed.available?
+  self.provider = X25519::Provider::Precomputed if X25519::Provider::Precomputed.available?
 
-  # Selected provider based on the logic above
-  def provider
-    @provider
-  end
-
   # Raw Diffie-Hellman function that acts directly on bytestrings. An
   # alternative to the object-oriented API
   #
   # @param scalar_bytes [String] a serialized private scalar
   # @param montgomery_u_bytes [String] a point we wish to multiply by the scalar
@@ -54,15 +57,15 @@
 
   # Perform a self-test to ensure the selected provider is working
   def self_test
     X25519::TestVectors::VARIABLE_BASE.each do |v|
       shared_secret = provider.scalarmult([v.scalar].pack("H*"), [v.input_coord].pack("H*"))
-      raise "self test failed!" unless shared_secret.unpack("H*").first == v.output_coord
+      raise SelfTestFailure, "self test failed!" unless shared_secret.unpack("H*").first == v.output_coord
     end
 
     X25519::TestVectors::FIXED_BASE.each do |v|
       public_key = provider.scalarmult_base([v.scalar].pack("H*"))
-      raise "self test failed!" unless public_key.unpack("H*").first == v.output_coord
+      raise SelfTestFailure, "self test failed!" unless public_key.unpack("H*").first == v.output_coord
     end
 
     true
   end
 end