diff --git a/lib/secure-random-string.js b/lib/secure-random-string.js
index 972e5f9..e15dbdf 100644
--- a/lib/secure-random-string.js
+++ b/lib/secure-random-string.js
@@ -9,7 +9,7 @@ function srs(options, cb) {
 	}
 
 	var length = options['length'] || 32;
-
+	var alphanumeric = options['alphanumeric'] || false;
 	// async path
 	if (cb) {
 		crypto.randomBytes(length, function(err, buf) {
@@ -26,7 +26,11 @@ function srs(options, cb) {
 
 	function _finish (buf) {
 		var string = buf.toString('base64');
-		string = string.replace(/\//g,'_').replace(/\+/g,'-');
+		if (alphanumeric === true){
+			string = string.replace(/[\W_]+/g,'');
+		}else{
+			string = string.replace(/\//g,'_').replace(/\+/g,'-');
+		}
 		return string.substr(0, length);
 	}