Encrypted File System

The EFS makes it trivially easy for developers to include cryptographic storage capabilities in their (embedded) products, facilitating this functionality with a minimal coding footprint.

Easy to use

Because EFS is implemented as a separate layer any existing generic file handling library can be used. Adding EFS on top of elm-chan FatFS or a Linux file module is a matter of minutes. Your file handling needs to have only the most common methods enabled. EFS is ideally suited to add encryption capabilities to your FAT formatted SD card.

Safe and Flexible

Based on the proven Linux secure file system white paper to ensure a solid design base. Every file is protected with a unique session key and can only be decrypted by the host who created it. For those files where performance is more a concern than security you can still read and write plain files. Adding more encryption algoritms is easily done as full source code is supplied.


Written specifically to be used in conjunction with embedded file systems our EFS uses very little RAM and ROM. No need for dynamic memory allocation. Random access without the need to keep the whole file in memory. Not even temporarily.


  • Proven reliability
  • Solid design base
  • Plain and encrypted files mixed on a single partitiion
  • Unique key for each file
  • Flexible choice in encryption methods
  • File decryption limited to the host which created the file
  • 100% compatible with FatFS from elm-chan.org
  • Low Memory usage: 40 bytes (!)
  • Minimal code footprint: ~2400 bytes on ARM thumb
  • Calls only 6 common file methods (7 if you want truncate)
  • Open: u get full source code
  • Unbeatable price. Unless your software engineer can build and debug similar functionality in three days.