FreeOTFE4PDA is an open source, "on-the-fly" (OTFE) transparent disk encryption program. Using this software, you can create one or more "virtual memory cards" on your PDA - anything written to which will be automatically, and securely, encrypted before being stored.

Features include:
- Source code freely available: Easy to use; full wizard included for creating new volumes;
- Powerful: Supports numerous hash/encryption algorithms, and provides a greater level of flexibility than a number of other (including commercial) OTFE systems;
- Hash algorithms include: MD5, SHA-512, RIPEMD-160, Tiger;
- Cyphers include AES (256 bit), Twofish (256 bit), Blowfish (448 bit), Serpent (256 bit);
- "Hidden" volumes may be concealed within other FreeOTFE volumes, providing "plausible deniability";
PC version is also available, allowing data encrypted on your PC to be read/written on your PDA, and vice versa.