FreeOTP is a two-factor authentication application for systems utilizing one-time password protocols with support for Android (4.0 or later) and iOS (7 or later). Tokens can be added easily by scanning a QR-code or by manually entering in the token configuration.
FreeOTP implements open standards. This means that no proprietary server-side component is necessary: use any server-side component that implements these standards. We personally recommend FreeIPA, which uses TOTP. However, any standards-compliant implementation will work. Currently, FreeOTP provides implementations of HOTP and TOTP.