README: The scyther-proof security protocol verification tool

Authors: Simon Meier iridcode@gmail.com Creation Date: 2011-05-13 Last Updated: 2013-02-27 by Andreas Lochbihler andreas.lochbihler@inf.ethz.ch

1. Introduction ===============

Every distribution of the scyther-proof tool contains a copy of the Isabelle/HOL theories formalizing its verification theory and a copy of the protocol models that were verified using scyther-proof. In particular, these examples include models for all of our repaired versions of the protocols from the ISO/IEC-9798 authentication standard. (In the source distribution of scyther-proof they can be found at data/examples/iso9798.)

In the following sections, we give step by step instructions to get the whole system working and we explain the usage of our tools and provide further information (e.g., building documentation).

2. Installation instructions ============================

2.1 Installing scyther-proof

You need a working Haskell environment that provides a version of GHC from 7.0.x to 7.4.x and the 'cabal install' tool. The simplest way to get such an environment is to download and install the Haskell Platform package for your OS.

http://hackage.haskell.org/platform/

Then call

cabal install

in the root directory of this source code package. This will use the Haskell's deployment tool cabal-install to download all missing libraries from Hackage, the central Haskell library repository and install the scyther-proof executable in the default installation location of cabal-install. The installation location is printed at the end of the build process.

Call

scyther-proof

without any arguments to get an overview of the arguments supported and the paths to the examples and the Isabelle/HOL theories.

2.2 Installing the Isabelle/HOL theories

Download and install full Isabelle2013 according to the installation instructions at

http://isabelle.in.tum.de/website-Isabelle2013/download_x86-linux.html

The first time you call scyther-proof with the --isabelle flag it will build the logic image of the Isabelle/HOL theories formalizing the security protocol verification theory underlying scyther-proof.

If you wish to use ProofGeneral to interactively process the theory files using our extensions to Isabelle's ISAR proof language, use one of the following two variants. This is needed in order to make the new ISAR keywords role, protocol, sources, and prefix_close available in the Emacs frontend. If you are using the Isabelle/jEdit Prover IDE, the keywords are automatically registered.

Variant a: Brute Force

Copy the Emacs keywords file provided with the ESPL distribution at

$SCYTHER_PROOF_HOME/data/isabelle/src/isar-keywords.el

to your local Isabelle configuration in

$ISABELLE_HOME_USER/etc

This will replace any custom keyword file that you have already installed in that way. You can find out about $ISABELLE_HOME_USER by running

isabelle getenv ISABELLE_HOME_USER

Variant b: Elegance

A more elegant way is to copy the keywords file provided with our distribution to

$ISABELLE_HOME_USER/etc/isar-keywords-ESPL.el

and start Isabelle using the -k switch as follows.

isabelle emacs -k ESPL <your-theory-file.thy>

3. Usage ========

3.1 scyther-proof

Usage Example

You can now execute the 'scyther-proof' binary without any arguments to get a list of the available flags. A simple example usage is (assuming 'scyther-proof' is in the PATH).

scyther-proof $EXAMPLE_DIR/classic/NS_Public.spthy --shortest

This will parse the NSL protocol modeled in the 'nsl.spthy' file and output all specified security properties together with the proof with the fewest number of chain rule applications to stdout.

To generate an Isabelle proof script, two additional options are required.

scyther-proof $EXAMPLE_DIR/classic/NS_Public.spthy --shortest --output=nsl_cert.thy --ASCII

The first one specifies the output file and the second one instructs scyther-proof to use Isabelle's ASCII notation as the output format.

To build the source code documentation you can use the call

cabal configure; cabal haddock

which will use cabal-install and Haskell's source code documentation tool 'haddock' to build the source code documentation. The location of this documentation is again output on the command line.

3.2 The Isabelle/HOL theories

Note that in many case the easiest way to start with constructing machine-checked proofs interactively is to use a proof script generated by scyther-proof.

Using ProofGeneral

In the directory output by scyther-proof, load the Tutorial on interactive proof construction using the following commands

    cd <theory-dir-output-by-scytherproof>/src
    isabelle emacs Tutorial.thy

or if you've chosen the elegant variant for the keywords file

    isabelle emacs -k ESPL Tutorial.thy

Using the Isabelle/jEdit Prover IDE

In the directory output by scyther-proof, load the Tutorial on interactive proof construction using the following commands

    cd <theory-dir-output-by-scytherproof>/src
    isabelle jedit -d $SCYTHER_PROOF_HOME/data/isabelle -l ESPL Tutorial.thy

where $SCYTHER_PROOF_HOME expands to the home directory of scyther-proof.

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Happy Proving :)

In case of questions do not hesistate to contact Simon Meier at iridcode@gmail.com.