Cryptol, version 2
This version of Cryptol is (C) 2013-2016 Galois, Inc., and distributed under a standard, three-clause BSD license. Please see the file LICENSE, distributed with this software, for specific terms and conditions.
What is Cryptol?
The Cryptol specification language was designed by Galois for the NSA’s Trusted Systems Research Group as a public standard for specifying cryptographic algorithms. A Cryptol reference specification can serve as the formal documentation for a cryptographic module. Unlike current specification mechanisms, Cryptol is fully executable, allowing designers to experiment with their programs incrementally as their designs evolve.
This release is an interpreter for version 2 of the Cryptol
language. The interpreter includes a
:check command, which tests
predicates written in Cryptol against randomly-generated test vectors
(in the style of
QuickCheck). There is
:prove command, which calls out to SMT solvers, such as
Yices, Z3, or CVC4, to prove predicates for all possible inputs.
Getting Cryptol Binaries
Cryptol binaries for Mac OS X, Linux, and Windows are available from
releases page. Mac OS
X and Linux binaries are distributed as a tarball which you can
extract to a location of your choice. Windows binaries are distributed
.msi installer package which places a shortcut to the Cryptol
interpreter in the Start menu.
On Mac OS X, Cryptol is also available via
Homebrew. Simply run
brew update && brew install
cryptol to get the latest stable version.
Cryptol currently uses Microsoft Research’s
Z3 SMT solver by default to solve
constraints during type checking, and as the default solver for the
:prove commands. You can download Z3 binaries for a
variety of platforms from their
releases page. Note that if you
install Cryptol using Homebrew, Z3 will be installed automatically.
After installation, make sure that
z3.exe on Windows)
is on your PATH.
Note for 64-bit Linux Users
On some 64-bit Linux configurations, 32-bit binaries do not work. This
can lead to unhelpful error messages like
z3: no such file or
directory, even when
z3 is clearly present. To fix this, either
install 32-bit compatibility packages for your distribution, or
x64 version of Z3.
Building Cryptol From Source
In addition to the binaries, the Cryptol source is available publicly on GitHub.
Cryptol builds and runs on various flavors of Linux, Mac OS X, and Windows. We regularly build and test it in the following environments:
- Mac OS X 10.10 64-bit
- CentOS 6 32⁄64-bit
- Windows 7 32-bit
Cryptol is developed using GHC 7.10.2 and cabal-install 1.22, though it is still tested with the previous major version of GHC. The easiest way to get the correct versions is to follow the instructions on the haskell.org downloads page.
Some supporting non-Haskell libraries are required to build Cryptol. Most should already be present for your operating system, but you may need to install the following:
You’ll also need Z3 installed when running Cryptol.
From the Cryptol source directory, run:
This will build Cryptol in place. From there, there are additional targets:
make run: run Cryptol in the current directory
make test: run the regression test suite (note: 4 failures is expected)
make docs: build the Cryptol documentation (requires pandoc and TeX Live)
make tarball: build a tarball with a relocatable Cryptol binary and documentation
make dist: build a platform-specific distribution. On all platforms except Windows, this is currently equivalent to
make tarball. On Windows, this will build an
.msipackage using WiX Toolset 3.8, which must be installed separately.
If you run
cabal install in your source directory after running one
make targets, you will end up with a binary in
.cabal-sandbox/bin/cryptol. You can either use that binary directly,
or use the results of
dist to install Cryptol in a
location of your choice.
We believe that anyone who uses Cryptol is making an important contribution toward making Cryptol a better tool. There are many ways to get involved.
If you write Cryptol programs that you think would benefit the
community, fork the GitHub repository, and add them to the
examples/contrib directory and submit a pull request.
We host a Cryptol mailing list, which you can join here.
If you run into a bug in Cryptol, if something doesn’t make sense in the documentation, if you think something could be better, or if you just have a cool use of Cryptol that you’d like to share with us, use the issues page on GitHub, or send email to [email protected].
If you’d like to get involved with Cryptol development, see the list of low-hanging fruit. These are tasks which should be straightforward to implement. Make a fork of this GitHub repository, send along pull requests and we’ll be happy to incorporate your changes.
/cryptol: Haskell sources for the front-end
cryptolexecutable and read-eval-print loop
/docs: LaTeX and Markdown sources for the Cryptol documentation
/examples: Cryptol sources implementing several interesting algorithms
/lib: Cryptol standard library sources
/src: Haskell sources for the
cryptollibrary (the bulk of the implementation)
/tests: Haskell sources for the Cryptol regression test suite, as well as the Cryptol sources and expected outputs that comprise that suite
Cryptol Notebook (Experimental)
The ICryptol notebook interface is now a standalone project.
Cryptol Server and pycryptol (Experimental)
This package includes an executable in
/cryptol-server that provides
an interface to the Cryptol interpreter via JSON over
ZeroMQ. Currently this is used to support the
pycryptol library. It
is part of this package because we intend to eventually make the
console REPL a client of that server as well. The
executable is included in any builds if the
environment variable is non-empty when running
make, for example:
CRYPTOL_SERVER=1 make dist
Where to Look Next
docs directory of the installation package contains an
introductory book, the
examples directory contains a number of
algorithms specified in Cryptol.
If you are familiar with version 1 of Cryptol, you should read the
Version2Changes document in the
Cryptol is still under active development at Galois. We are also building tools that consume both Cryptol specifications and implementations in (for example) C or Java, and can (with some amount of work) allow you to verify that an implementation meets its specification. Email us at [email protected] if you’re interested in these capabilities.
We hope that Cryptol is useful as a tool for educators and students, commercial and open source authors of cryptographic implementations, and by cryptographers to
- specify cryptographic algorithms
- check or prove properties of algorithms
- generate test vectors for testing implementations
- experiment with new algorithms
Cryptol has been under development for over a decade with many people contributing to its design and implementation. Those people include (but are not limited to) Iavor Diatchki, Aaron Tomb, Adam Wick, Brian Huffman, Dylan McNamee, Joe Kiniry, John Launchbury, Matt Sottile, Adam Foltzer, Joe Hendrix, Trevor Elliott, Lee Pike, Mark Tullsen, Levent Erkök, David Lazar, Joel Stanley, Jeff Lewis, Andy Gill, Edward Yang, Ledah Casburn, Jim Teisher, Sigbjørn Finne, Mark Shields, Philip Weaver, Magnus Carlsson, Fergus Henderson, Joe Hurd, Thomas Nordin, John Matthews and Sally Browning. In addition, much of the work on Cryptol has been funded by, and lots of design input was provided by the team at the NSA’s Trusted Systems Research Group, including Brad Martin, Frank Taylor and Sean Weaver.