diff --git a/lib/rack/auth/basic.rb b/lib/rack/auth/basic.rb
index d5b4ea16d..11dab9797 100644
--- a/lib/rack/auth/basic.rb
+++ b/lib/rack/auth/basic.rb
@@ -2,7 +2,6 @@
 
 require_relative 'abstract/handler'
 require_relative 'abstract/request'
-require 'base64'
 
 module Rack
   module Auth
@@ -48,7 +47,7 @@ def basic?
         end
 
         def credentials
-          @credentials ||= Base64.decode64(params).split(':', 2)
+          @credentials ||= params.unpack("m").first.split(':', 2)
         end
 
         def username
diff --git a/lib/rack/auth/digest/nonce.rb b/lib/rack/auth/digest/nonce.rb
index 3216d973e..ec871c806 100644
--- a/lib/rack/auth/digest/nonce.rb
+++ b/lib/rack/auth/digest/nonce.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require 'digest/md5'
-require 'base64'
 
 module Rack
   module Auth
@@ -21,7 +20,7 @@ class << self
         end
 
         def self.parse(string)
-          new(*Base64.decode64(string).split(' ', 2))
+          new(*string.unpack("m").first.split(' ', 2))
         end
 
         def initialize(timestamp = Time.now, given_digest = nil)
@@ -29,7 +28,7 @@ def initialize(timestamp = Time.now, given_digest = nil)
         end
 
         def to_s
-          Base64.encode64("#{@timestamp} #{digest}").strip
+          ["#{@timestamp} #{digest}"].pack("m0")
         end
 
         def digest
diff --git a/lib/rack/session/cookie.rb b/lib/rack/session/cookie.rb
index 737c0b33b..3f1fc8a7a 100644
--- a/lib/rack/session/cookie.rb
+++ b/lib/rack/session/cookie.rb
@@ -4,7 +4,6 @@
 require 'zlib'
 require_relative 'abstract/id'
 require 'json'
-require 'base64'
 require 'delegate'
 
 module Rack
@@ -51,11 +50,11 @@ class Cookie < Abstract::PersistedSecure
       # Encode session cookies as Base64
       class Base64
         def encode(str)
-          ::Base64.strict_encode64(str)
+          [str].pack("m0")
         end
 
         def decode(str)
-          ::Base64.decode64(str)
+          str.unpack("m").first
         end
 
         # Encode session cookies as Marshaled Base64 data