Implemented the RSA::Math.log, .log2 and .log256 methods.

lib/rsa/key_pair.rb

@@ -66,15 +66,15 @@ def valid?
     #
     # @return [Integer]
     def bytesize
-      ::Math.log(modulus, 256).ceil
+      Math.log256(modulus).ceil
     end
 
     ##
     # Returns the bit size of this key pair.
     #
     # @return [Integer]
     def bitsize
-      ::Math.log2(modulus).ceil
+      Math.log2(modulus).ceil
     end
     alias_method :size, :bitsize
 
@@ -103,7 +103,7 @@ def encrypt(plaintext, options = {})
         else raise ArgumentError, plaintext.inspect
       end
       ciphertext = PKCS1.rsaep(public_key, plaintext)
-      PKCS1.i2osp(ciphertext, ::Math.log(ciphertext, 256).ceil)
+      PKCS1.i2osp(ciphertext, Math.log256(ciphertext).ceil)
     end
 
     ##
@@ -122,7 +122,7 @@ def decrypt(ciphertext, options = {})
         else raise ArgumentError, ciphertext.inspect
       end
       plaintext = PKCS1.rsadp(private_key, ciphertext)
-      PKCS1.i2osp(plaintext, ::Math.log(plaintext, 256).ceil)
+      PKCS1.i2osp(plaintext, Math.log256(plaintext).ceil)
     end
 
     ##
@@ -140,7 +140,7 @@ def sign(plaintext, options = {})
         else raise ArgumentError, plaintext.inspect
       end
       signature = PKCS1.rsasp1(private_key, plaintext)
-      PKCS1.i2osp(signature, ::Math.log(signature, 256).ceil)
+      PKCS1.i2osp(signature, Math.log256(signature).ceil)
     end
   end # class KeyPair
 end # module RSA

lib/rsa/math.rb

@@ -4,10 +4,6 @@ module RSA
   module Math
     extend ::Math
 
-    class << self
-      public :log, :log2
-    end
-
     ##
     # Performs a primality test on the integer `n`, returning `true` if it
     # is a prime.
@@ -68,5 +64,37 @@ def self.modpow(base, exponent, modulus)
     def self.phi(n)
       1 + (2...n).count { |i| i.gcd(n).eql?(1) }
     end
+
+    ##
+    # Returns the binary logarithm of `n`.
+    #
+    # @param  [Integer] n
+    # @return [Float]
+    # @see    http://en.wikipedia.org/wiki/Binary_logarithm
+    def self.log2(n)
+      ::Math.log2(n)
+    end
+
+    ##
+    # Returns the base-256 logarithm of `n`.
+    #
+    # @param  [Integer] n
+    # @return [Float]
+    # @see    http://en.wikipedia.org/wiki/Logarithm
+    def self.log256(n)
+      ::Math.log(n, 256)
+    end
+
+    ##
+    # Returns the natural logarithm of `n`. If the optional argument `b` is
+    # given, it will be used as the base of the logarithm.
+    #
+    # @param  [Integer] n
+    # @param  [Integer] b
+    # @return [Float]
+    # @see    http://en.wikipedia.org/wiki/Natural_logarithm
+    def self.log(n, b = nil)
+      b ? ::Math.log(n, b) : ::Math.log(n)
+    end
   end
 end