Sample BAT: CLAUS++ version 1

CLAUS++ is, cryptographically, a very simple form of the Diffie-Hellman secret-sharing system: it exponentiates modulo a fixed 1024-bit prime. CLAUS++ doesn't contain many lines of code: it relies on the popular GMP and NTL arithmetic libraries to generate keys and to compute shared secrets. Other BAT implementors may find CLAUS++ useful as an illustration of the ease of writing BATs.

CLAUS is a similar BAT written in C rather than C++.

Core files

     #define SECRETKEY_BYTES 256
     #define PUBLICKEY_BYTES 128
     #define SHAREDSECRET_BYTES 128

Another file, claus++-1/keypair.cpp, defines a keypair() function that generates a secret key and a public key:

     int keypair(
       unsigned char *sk,unsigned long long *sklen,
       unsigned char *pk,unsigned long long *pklen
     )
     {
       ...
     }

Another file, claus++-1/sharedsecret.cpp, defines a sharedsecret() function that generates a shared secret:

     int sharedsecret(
       unsigned char *s,unsigned long long *slen,
       const unsigned char *sk,unsigned long long sklen,
       const unsigned char *pk,unsigned long long pklen
     )
     {
       ...
     }

There's no special naming convention for the .cpp files and .h files other than sizes.h. All of the C++ functions could have been defined in one file or spread among any number of files. All of these files are automatically compiled together by the eBATS benchmarking tools.

At a lower level, keypair.cpp and sharedsecret.cpp can use the NTL library for arithmetic, but they instead use the GMP library for arithmetic if they're compiled with -DGMP, GMP and NTL are automatically made available to all BATs.

These two options are listed in another file, claus++-1/tunings:

     -DTUNING="NTL"
     -DGMP -DTUNING="GMP"

Add-on files

• The copyrightclaims function returns 0 to indicate that there are no known copyright claims against distribution of CLAUS++.
• The patentclaims function returns 0 to indicate that there are no known patent claims against use of CLAUS++.
• The multiplekeycdhchance function reports the effectiveness of the best e-euro s-second k-key attack known, namely computing 1024-bit multiplicative-group discrete logarithms:

       double multiplekeycdhchance(double e,double s,double k)
       {
         return dlchance(1024,e,s,k);
       }
  

  The underlying dlchance function is part of eBATS and didn't require any work by the CLAUS++ programmer.
• The simplified cdhchance function reports the effectiveness of the best e-euro s-second single-key attack known.
• The fakekeyattacks function returns 0 to indicate that providing fake public keys does not save time in attacks.

One last file, claus++-1/documentation.pdf, contains references and other comments for cryptographers. This file isn't used in any way by the benchmarking tools but it's still an important part of a BAT.

Version