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Free and simple TrueCrypt Implementation based on dm-crypt
branch: master
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test add basic API save/restore header tests
.gitignore .gitignore: update
CHANGELOG finalize changelog for 2.0
CMakeLists.txt slowly prepare 2.0
LICENSE doc - add a LICENSE file
Makefile.classic slowly prepare 2.0 update README for 2.0
crc32.c first step to porting to linux; can be broken :)
crc32.h first step to porting to linux; can be broken :)
crypto-dev.c fix DragonFly compilation
crypto-gcrypt.c Use proper gcrypt initialization
crypto.c Fix typo
generic_xts.c big cleanup; Makefile is now gnu make
generic_xts.h separate out bits; implement gcrypt backend
hdr.c use internal disksz_t instead of size_t for large block/byte sizes
humanize.c big cleanup; Makefile is now gnu make
humanize.h add humanize functions
io.c dragonfly - fix i386 compile error
main.c add undocumented --no-retries to make testing easier
pbkdf2-gcrypt.c Work around broken gcrypt includes
pbkdf2-openssl.c big cleanup; Makefile is now gnu make
safe_mem.c first pass refactoring
tcplay.3 tcplay: Fix a function name in tcplay.3 and .Dd in tcplay.8.
tcplay.8 tcplay.8 - don't use a non-existant chipher in examples
tcplay.c fix warning on DragonFly
tcplay.h new API - add back error function; throw in new state change callback tests & fixes for cipher/prf iterators
tcplay_api.c Detect NULL arg to *task_set
tcplay_api.h new API - add back error function; throw in new state change callback
tcplay_api_internal.h work around the usual C++ fun
tcplay_api_test.c make blksz agnostic, fix volume size


tcplay is a free (BSD-licensed), pretty much fully featured (including multiple keyfiles, cipher cascades, etc) and stable TrueCrypt implementation.

This implementation supports mapping (opening) both system and normal TrueCrypt volumes, as well as opening hidden volumes and opening an outer volume while protecting a hidden volume. There is also support to create volumes, including hidden volumes, etc. Since version 1.1, there is also support for restoring from the backup header (if present), change passphrase, keyfile and PBKDF2 PRF function.

Since tcplay uses dm-crypt (or dm_target_crypt on DragonFly) it makes full use of any available hardware encryption/decryption support once the volume has been mapped.

It is based solely on the documentation available on the TrueCrypt website, many hours of trial and error and the output of the Linux' TrueCrypt client. As it turns out, most technical documents on TrueCrypt contain mistakes, hence the trial and error approach.

Implementation notes

DragonFly BSD uses the hybrid OpenSSL + cryptodev(9) approach that can be found in crypto-dev.c. OpenSSL is only used for the hash/pbkdf2. The encryption/decryption is performed via cryptodev(9) with enabled cryptosoft.

On Linux gcrypt is used for the encryption and decryption. For the hash/pbkdf2 either gcrypt or OpenSSL can be used. gcrypt only supports pbkdf2 since its July 2011 release (1.5.0), while OpenSSL has had pbkdf2 since around December 2010, so its easier to find in most distros.

The crypto options can be chosen with make/Makefile parameters. Building on Linux is as easy as doing

make -f Makefile.classic SYSTEM=linux

you can even skip the SYSTEM=linux, since that's the default. To choose the PBKDF backend, you can use either,

make -f Makefile.classic PBKDF_BACKEND=openssl


make -f Makefile.classic PBKDF_BACKEND=gcrypt

The interface to device mapper is libdevmapper on Linux and libdm on DragonFly. libdm is a BSD-licensed version of libdevmapper that I hacked together in a few hours.

On Ubuntu, the following dev packages are needed to build tcplay:

apt-get install build-essential libdevmapper-dev libgcrypt11-dev uuid-dev


New in version 1.0 is a cmake build system. tcplay can now be built using:

mkdir objdir
cd objdir
cmake ..

NOTE: building inside the source directory is discouraged, so please do build inside an "objdir" directory. If you happen to do it anyway, you can clean up behind cmake using:

make -f Makefile.classic clean_cmake_mess

Before running cmake, make sure you have pkg-config installed; e.g. on a Debian or Ubuntu system you can install it using:

apt-get install pkg-config

This process will check for dependencies and automatically select whether to use OpenSSL or gcrypt as PBKDF backend.

In addition, this process will also generate a .pc file (pkg-config) for the tcplay library.

The classic single-file Makefile can still be used for building, however, using

make -f Makefile.classic

Or, if you only want the command line tool:

make -f Makefile.classic tcplay


In addition to providing a command line tool, tcplay is also available as a library. See the tcplay.3 man page for more details on how to use the API.

TODO: link examples


Please refer to the man pages bundled with tcplay.

Download for packaging

Latest release can be found as a (source) tarball at:


Please report all bugs on the github issue tracker. If appropriate, please attach a small test volume which you think tcplay isn't handling correctly. The script in test/ can significantly reduce the size of a volume when compressed by stripping out all the unnecessary data, leaving only the headers. After that, just bzip2 it and it should be fairly tiny.

What would be even better is if you could write a small test case to reproduce the issue. The README in the test/ directory has information on how to write tests for tcplay.

OS Support

tcplay is now available for both DragonFly BSD and Linux. It is a core part of the DragonFly BSD operating system and is available in a number of linux distros.


The project is under a two-clause BSD license. I would consider dual-licensing it if required. Drop me an email to discuss the options.


tcplay is pretty much stable, but if you find a bug, please report it. If anyone wants to add new features or port it to another OS, I'll gladly merge your changes into this repository so that there is a single point of contact.

I've noticed that sometimes bugs are only reported downstream (e.g. in the distro's bugtracker). Please make sure those bugs are also reported upstream on github, otherwise odds are they will never reach me.

Bugs in the TrueCrypt documentation

The TrueCrypt documentation is pretty bad and does not really represent the actual on-disk format nor the encryption/decryption process.

Some notable differences between actual implementation and documentation:

  • PBKDF using RIPEMD160 only uses 2000 iterations if the volume isn't a system volume.
  • The keyfile pool is not XOR'ed with the passphrase but modulo-256 summed.
  • Every field except the minimum version field of the volume header are in big endian.
  • Some volume header fields (creation time of volume and header) are missing in the documentation.
  • All two-way cipher cascades are the wrong way round in the documentation, but all three-way cipher cascades are correct.
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