Linux Kernel Crypto API User Space Interface Library
C Shell Perl Other
Fetching latest commit…
Cannot retrieve the latest commit at this time.

libkcapi -- Linux Kernel Crypto API User Space Interface Library

libkcapi allows user-space to access the Linux kernel crypto API.

libkcapi uses this Netlink interface and exports easy to use APIs so that a developer does not need to consider the low-level Netlink interface handling.

The library does not implement any cipher algorithms. All consumer requests are sent to the kernel for processing. Results from the kernel crypto API are returned to the consumer via the library API.

The kernel interface and therefore this library can be used by unprivileged processes.

The focus during the development of this library is put on speed. This library does not perform any memcpy for processing the cryptographic data! The library uses scatter / gather lists to eliminate the need for moving data around in memory.

Directory Structure

lib/ -- directory holding the library

apps/ -- directory holding the applications discussed below; these applications hard link the library code in.

test/ -- functional verification code

speed-test/ -- performance tests


The libkcapi distribution contains the following applications which are intended as a drop-in replacement for the respective applications commonly available in all Linux distributions:

  • coreutils: sha512sum, sha384sum, sha256sum, sha224sum, sha1sum, md5sum

  • libfipscheck: fipscheck / fipshmac

  • hmaccalc: sha512hmac, sha384hmac, sha256hmac, sha224hmac, sha1hmac

The output as well as the command line options are modeled according to the commands found in the coreutils package.

These applications do not depend on any user space library other than the C-lib.

Version Numbers

The version numbers for this library have the following schema: MAJOR.MINOR.PATCHLEVEL

Changes in the major number implies API and ABI incompatible changes, or functional changes that require consumer to be updated (as long as this number is zero, the API is not considered stable and can change without a bump of the major version).

Changes in the minor version are API compatible, but the ABI may change. Functional enhancements only are added. Thus, a consumer can be left unchanged if enhancements are not considered. The consumer only needs to be recompiled.

Patchlevel changes are API / ABI compatible. No functional changes, no enhancements are made. This release is a bug fixe release only. The consumer can be left unchanged and does not need to be recompiled.

Build instructions

The build system is based on autotools. First of all, you have to run the following command that will generate the Makefile and the configure script:

$ autoreconf -i

The configure script supports the following options:

  • --prefix=$PREFIX: install the library and the applications to $PREFIX
  • --with-kcapi-test: compile and install the kcapi test program
  • --with-kcapi-speed: compile and install kcapi-speed test program
  • --with-apps: compile and install the applications

For instance, to compile the library with the kcapi test program and to install them in /usr/:

$ ./configure --prefix=/usr/ --with-kcapi-test

Then, run make to compile and make install to install in the folder specified by the --prefix option.

The Makefile compiles libkcapi as a shared library and as a static libary.

Build documentation

xmlto is required to build the man pages and the documentation in doc/html. db2pdf and db2ps are required to build the documentation in PDF or in PS format.

Use the following targets to generate the documentation in the appropriate format:

  • make man
  • make pdf
  • make ps
  • make html

To install the man pages run: make install-man.

Static Code analyzer

If clang or cppcheck are installed, you can use the following targets to run them on the source code:

  • make scan
  • make cppcheck

Test cases

The test/ directory contains test cases to verify the correct operation of this library. In addition it allows the verification of the correct operation of the kernel crypto API.

The test cases are documented in test/README.

Kernel Patches

With the current cryptodev-2.6 tree from Herbert Xu, all patches are integrated.


Stephan Mueller