lib/noise/functions/cipher/cha_cha_poly.rb in noise-ruby-0.7.3 vs lib/noise/functions/cipher/cha_cha_poly.rb in noise-ruby-0.7.4

@@ -2,25 +2,37 @@
 
 module Noise
   module Functions
     module Cipher
       class ChaChaPoly
+        MAX_NONCE = 2**64 - 1
+
         def encrypt(k, n, ad, plaintext)
-          @cipher = RbNaCl::AEAD::ChaCha20Poly1305IETF.new(String.new(k).force_encoding('ASCII-8BIT'))
-          @cipher.encrypt(nonce_to_bytes(n), plaintext, ad)
+          cipher = RbNaCl::AEAD::ChaCha20Poly1305IETF.new(String.new(k).force_encoding('ASCII-8BIT'))
+          cipher.encrypt(nonce_to_bytes(n), plaintext, ad)
         rescue ::RbNaCl::CryptoError => e
           raise Noise::Exceptions::EncryptError, e
         end
 
         def decrypt(k, n, ad, ciphertext)
-          @cipher = RbNaCl::AEAD::ChaCha20Poly1305IETF.new(String.new(k).force_encoding('ASCII-8BIT'))
-          @cipher.decrypt(nonce_to_bytes(n), ciphertext, ad)
+          cipher = RbNaCl::AEAD::ChaCha20Poly1305IETF.new(String.new(k).force_encoding('ASCII-8BIT'))
+          cipher.decrypt(nonce_to_bytes(n), ciphertext, ad)
         rescue ::RbNaCl::CryptoError => e
           raise Noise::Exceptions::DecryptError, e
         end
 
         def nonce_to_bytes(n)
           "\x00" * 4 + format('%16x', n).htb.reverse
+        end
+
+        # Returns a new 32-byte cipher key as a pseudorandom function of k.
+        # If this function is not specifically defined for some set of cipher
+        # functions, then it defaults to returning the first 32 bytes from
+        # ENCRYPT(k,maxnonce, zerolen, zeros), where  maxnonce equals 2**64-1,
+        # zerolen is a zero-length byte sequence, and zeros is a sequence of
+        # 32 bytes filled with zeros.
+        def rekey(k)
+          encrypt(k, MAX_NONCE, '', "\x00" * 32)[0..32]
         end
       end
     end
   end
 end