1 files changed, 42 insertions, 0 deletions
diff --git a/lib/json_web_token/rsa_token.rb b/lib/json_web_token/rsa_token.rb
new file mode 100644
index 00000000000..d6d6af7089c
--- /dev/null
+++ b/lib/json_web_token/rsa_token.rb
@@ -0,0 +1,42 @@
+module JSONWebToken
+  class RSAToken < Token
+    attr_reader :key_file
+
+    def initialize(key_file)
+      super()
+      @key_file = key_file
+    end
+
+    def encoded
+      headers = {
+        kid: kid
+      }
+      JWT.encode(payload, key, 'RS256', headers)
+    end
+
+    private
+
+    def key_data
+      @key_data ||= File.read(key_file)
+    end
+
+    def key
+      @key ||= OpenSSL::PKey::RSA.new(key_data)
+    end
+
+    def public_key
+      key.public_key
+    end
+
+    def kid
+      # calculate sha256 from DER encoded ASN1
+      kid = Digest::SHA256.digest(public_key.to_der)
+
+      # we encode only 30 bytes with base32
+      kid = Base32.encode(kid[0..29])
+
+      # insert colon every 4 characters
+      kid.scan(/.{4}/).join(':')
+    end
+  end
+end