OTPdroid is a free One Time Password implementation for Android devices. It is designed to generate a password that is only valid for one login, making it ideal for logging into an OTP enabled system from an untrusted terminal. OTPdroid supports both SHA1 and MD5 encryption algorithms, offering flexibility to users.

One of the most notable features of OTPdroid is its option to store passphrase and challenge, which are encrypted with IMEI (device) and IMSI (sim) via AES-256. This ensures that the stored data is secure and cannot be accessed by unauthorized users. The app is easy to use and its user interface is simple and straightforward.

In summary, OTPdroid is an efficient and reliable One Time Password implementation for Android devices. Its support for SHA1 and MD5 encryption algorithms, as well as its secure storage option, make it a great option for users who prioritize security and privacy.