diff --git a/src/clientAuth/clientAuth.js b/src/clientAuth/clientAuth.js
new file mode 100644
index 0000000..fbc067d
--- /dev/null
+++ b/src/clientAuth/clientAuth.js
@@ -0,0 +1,34 @@
+/**
+ * @fileoverview Adds authentication information to a request and validates
+ * client info.
+ */
+
+const OICCli = require('../init.js').OICCli;
+const utf8 = require('utf8');
+const base64url = require('base64url');
+
+/**
+ * ClientAuthnMethod
+ * Basic Client Authentication Method class.
+ * @class 
+ * @constructor
+ */
+class ClientAuthnMethod {
+  constructor() {}
+
+  construct(params) {
+    throw new Error('Unsupported Operation Exception');
+  }
+}
+
+function validServiceContext(serviceContext, when) {
+  let eta = serviceContext['client_secret_expires_at'] || 0;
+  let now = when || Date.now();
+  if (eta !== 0 && eta < now) {
+    return false;
+  }
+  return true;
+}
+
+module.exports.ClientAuthnMethod = ClientAuthnMethod;
+module.exports.validServiceContext = validServiceContext;
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diff --git a/test/clientAuth-test.js b/test/clientAuth-test.js
new file mode 100644
index 0000000..56941c9
--- /dev/null
+++ b/test/clientAuth-test.js
@@ -0,0 +1,19 @@
+const assert = require('chai').assert;
+const validServiceContext = require('../src/clientAuth/clientAuth').validServiceContext;
+
+describe('Test valid client info', function() {
+  let now = 123456;
+
+  it('test valid client info works', function() {
+    assert.isTrue(validServiceContext({}, now));
+    assert.isTrue(
+      validServiceContext({'client_id': 'test', 'client_secret': 'secret'}, now));
+    assert.isTrue(validServiceContext({'client_secret_expires_at': 0}, now));
+    assert.isTrue(validServiceContext({'client_secret_expires_at': 123460}, now));
+    assert.isTrue(validServiceContext(
+      {'client_id': 'test', 'client_secret_expires_at': 123460}, now));
+    assert.isFalse(validServiceContext({'client_secret_expires_at': 1}, now));
+    assert.isFalse(validServiceContext(
+      {'client_id': 'test', 'client_secret_expires_at': 123455}, now));
+  });
+});
\ No newline at end of file