Monocypher (Developer Edition)

(This is the bleeding edge, not yet released version. If you just want to use Monocypher, grab the latest version, or download the source and header files directly. If you want to contribute, see the notes at the end.)

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Monocypher is an easy to use, easy to deploy, auditable crypto library written in portable C. It approaches the size of TweetNaCl and the speed of Libsodium.

Official site.
Official releases.

Features

• Authenticated Encryption with XChaCha20 and Poly1305 (RFC 8439).
• Hashing with BLAKE2b.
• Password Hashing with Argon2i.
• Public Key Cryptography with X25519 (key exchange).
• Public Key Signatures with EdDSA (RFC 8032) and Ed25519.
• Steganography support with Elligator 2.
• OPRF and PAKE support with Elligator 2 and scalar inversion.

Manual

The manual can be found at https://monocypher.org/manual/, and in the doc/ folder.

The doc/man/ folder contains the man pages. You can install them in your system by running make install-doc. Official releases also have a doc/html/ folder with an html version.

Installation

Option 1: grab the sources

The easiest way to use Monocypher is to include src/monocypher.h and src/monocypher.c directly into your project. They compile as C (since C99) and C++ (since C++98).

Option 2: grab the library

Run make, then grab the src/monocypher.h header and either the lib/libmonocypher.a or lib/libmonocypher.so library. The default compiler is gcc -std=gnu99, and the default flags are -pedantic -Wall -Wextra -O3 -march=native. If they don't work on your platform, you can change them like this:

$ make CC="clang -std=c99" CFLAGS="-O2"

Option 3: install it on your system

The following should work on most UNIX systems:

$ make install

This will install Monocypher in /usr/local/ by default. Libraries will go to /usr/local/lib/, the header in /usr/local/include/, and the man pages in /usr/local/share/man/man3. You can change those defaults with the PREFIX and DESTDIR variables thus:

$ make install PREFIX="/opt"

Once installed, you can use pkg-config to compile and link your program. For instance, if you have a one file C project that uses Monocypher, you can compile it thus:

$ gcc -o myProgram myProgram.c        \
    $(pkg-config monocypher --cflags) \
    $(pkg-config monocypher --libs)

The cflags line gives the include path for monocypher.h, and the libs line provides the link path and option required to find libmonocypher.a (or libmonocypher.so).

Test suite

$ make test

It should display a nice printout of all the tests, all starting with "OK". If you see "FAILURE" anywhere, something has gone very wrong somewhere.

Do not use Monocypher without running those tests at least once.

The same test suite can be run under Clang sanitisers and Valgrind, and be checked for code coverage:

$ tests/test.sh
$ tests/coverage.sh

Serious auditing

The code may be analysed more formally with Frama-c and the TIS interpreter. To analyse the code with Frama-c, run:

$ tests/formal-analysis.sh
$ tests/frama-c.sh

This will have Frama-c parse, and analyse the code, then launch a GUI. You must have Frama-c installed. See frama-c.sh for the recommended settings. To run the code under the TIS interpreter, run

$ tests/formal-analysis.sh
$ tis-interpreter.sh --cc -Dvolatile= tests/formal-analysis/*.c

Notes:

• tis-interpreter.sh is part of TIS. If it is not in your path, adjust the command accordingly.

• The TIS interpreter sometimes fails to evaluate correct programs when they use the volatile keyword (which is only used as an attempt to prevent dead store elimination for memory wipes). The -cc -Dvolatile= option works around that bug by ignoring volatile altogether.

Speed benchmark

$ make speed

This will give you an idea how fast Monocypher is on your machine. Make sure you run it on the target platform if performance is a concern. If Monocypher is too slow, try Libsodium. If you're not sure, you can always switch later.

Note: the speed benchmark currently requires the POSIX clock_gettime() function.

There are similar benchmarks for Libsodium, TweetNaCl, LibHydrogen, c25519, and ed25519-donna (the portable, 32-bit version):

$ make speed-sodium
$ make speed-tweetnacl
$ make speed-hydrogen
$ make speed-c25519
$ make speed-donna

(The speed-hydrogen target assumes it has pkg-config installed. Try make pkg-config-libhydrogen as root if it is not.)

You can also adjust the optimisation options for Monocypher, TweetNaCl, and c25519 (the default is -O3 march=native):

$ make speed           CFLAGS="-O2"
$ make speed-tweetnacl CFLAGS="-O2"

Customisation

Monocypher has optional compatibility with Ed25519. To have that, add monocypher-ed25519.h and monocypher-ed25519.c provided in src/optional to your project. If you're using the makefile, define the USE_ED25519 variable to link it to monocypher.a and monocypher.so:

$ make USE_ED25519=true

If you install Monocypher with the makefile, you also need that option to copy monocypher-ed25519.h automatically:

$ make install USE_ED25519=true

Monocypher also has the BLAKE2_NO_UNROLLING preprocessor flag, which is activated by compiling monocypher.c with the -DBLAKE2_NO_UNROLLING option.

The -DBLAKE2_NO_UNROLLING option is a performance tweak. By default, Monocypher unrolls the BLAKE2b inner loop, because doing so is over 25% faster on modern processors. Some embedded processors however, run the unrolled loop slower (possibly because of the cost of fetching 5KB of additional code). If you're using an embedded platform, try this option. The binary will be about 5KB smaller, and in some cases faster.

Contributor notes

If you are reading this, you cloned the GitHub repository. You miss a couple files that ship with the tarball releases:

• The tests/vectors.h header. Generating it requires Libsodium. Go to tests/gen/, then run make.
• The html version of the manual, generated by the doc/man2html.sh script. You will need mandoc.

To generate a tarball, simply type make dist. It will make a tarball with a name that matches the current version (using git describe), in the current directory.