This is code and CNF files for the bitcoin mining using SAT solver article.

The C file satcoin.c can be run in two modes. Either it can be compiled and executed with a compiler such as GCC, or it can be run using the bounded model checker CBMC. The model checker can be used to check the satisfiability of the C code or to generate DIMACS files as input to other SAT solvers.

The compilation can be used to verify that the hash calculation is actually performed correctly. By default the input to the program is the Genesis block, the output is the hash of the Genesis block as calculated by the program:

$ gcc satcoin.c -o satcoin
$ ./satcoin
00-00-00-00-00-19-d6-68-9c-08-5a-e1-65-83-1e-93-4f-f7-63-ae-46-a2-a6-c1-72-b3-f1-b6-0a-8c-e2-6f-

The nonce of the Genesis block is 497822588 and the hash is

000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f

In verification mode the nonce of the input block is overwritten with a non-deterministic value around line 109, then the range of the nonce is restricted with the CBMC-specific directive __CPROVER_assume.

The range of this assertion determines the difficulty of the CNF file. If the range includes the actual valid nonce of this block then the instance will be satisfiable, if it excludes the value then it will be unsatisfiable.

By default the range of the nonce is between 0 and 10, thus it will be unsatisfiable.

An unsatisfiable instance means there is no nonce that will satisfy the mining criteria.

$ cbmc -DCBMC satcoin.c
CBMC version 5.8 64-bit x86_64 macos
Parsing satcoin.c
Converting
Type-checking satcoin
file satcoin.c line 109 function verifyhash: function `nondet_uint' is not declared
file satcoin.c line 163 function verifyhash: function `assert' is not declared
Generating GOTO Program
Adding CPROVER library (x86_64)
Removal of function pointers and virtual functions
Partial Inlining
Generic Property Instrumentation
Starting Bounded Model Checking
....
Solving with MiniSAT 2.2.1 with simplifier
134717 variables, 648661 clauses
SAT checker: instance is UNSATISFIABLE
Runtime decision procedure: 0.661s

** Results:
[verifyhash.assertion.1] assertion flag == 1: SUCCESS

** 0 of 1 failed (1 iteration)
VERIFICATION SUCCESSFUL