gistfile1.cpp

#include <bits/stdc++.h>

using namespace std;

typedef unsigned long long ll;
typedef unsigned int uint;
typedef vector<unsigned char> SOLUTION;

struct STATE
{
	int path_count[6];
	uint magic;
	int current_func;

	ll __hash__() const
	{
		ll ans = 0;
		for(int i = 0;i < 6;i++) ans = ans * 8 + path_count[i];
		ans = ans * 8 + current_func;
		ans = (ans << 32ll) | magic;
		return ans;
	}
};

queue<STATE> q;
map<ll, SOLUTION> solution;

enum { A, B, C, D, E, F };

void try_push(const STATE& state, const STATE& old, unsigned char ch)
{
	ll nh = state.__hash__();
	if(solution.find(nh) == solution.end())
	{
		q.push(state);
		SOLUTION cs = solution[old.__hash__()];
		cs.push_back(ch);
		solution[nh] = cs;
	}
}

void path_a(const STATE& state, unsigned char ch)
{
	if(state.path_count[A] > 2) return;
	STATE nextState = state;
	nextState.path_count[A]++;
	nextState.magic = state.magic * 2;
	switch(ch % 3)
	{
	case 0:
		nextState.current_func = B;
		break;
	case 1:
		nextState.current_func = C;
		break;
	case 2:
		nextState.current_func = D;
		break;
	}
	try_push(nextState, state, ch);
}

void path_b(const STATE& state, unsigned char ch)
{
	if(state.path_count[B] > 2) return;
	STATE nextState = state;
	nextState.path_count[B]++;
	nextState.magic = state.magic + 27;
	if(ch % 117 > 30)
	{
		nextState.current_func = C;
	}
	else
	{
		nextState.current_func = A;
	}
	try_push(nextState, state, ch);
}

void path_key(const STATE& old, unsigned char ch)
{
	printf("[+] Solution found.\n");
	SOLUTION sol = solution[old.__hash__()];
	sol.push_back(ch);
	for(int i = 0;i < sol.size();i++) printf("%02x",sol[i]);
	puts("");
	exit(0);
}

void path_c(const STATE& state, unsigned char ch)
{
	if(state.path_count[C] > 1) return;
	STATE nextState = state;
	nextState.path_count[C]++;
	nextState.magic = state.magic + 17;
	if ( ch % 3 + (nextState.magic >> 4) == (nextState.magic & 0xF)
		&& (nextState.magic << ((unsigned int)ch & 7)) % 123 == 115
		&& nextState.magic > ch << nextState.magic % 3 )
		path_key(state, ch);

	switch(ch % 3)
	{
	case 0:
		nextState.current_func = D;
		break;
	case 1:
		nextState.current_func = F;
		break;
	case 2:
		nextState.current_func = F;
		break;
	}

	try_push(nextState, state, ch);
}

void path_d(const STATE& state, unsigned char ch)
{
	if(state.path_count[D] > 1) return;
	STATE nextState = state;
	nextState.path_count[D]++;
	nextState.magic = (unsigned char)(state.magic & 0x80) | (state.magic >> 1);

	if(ch + nextState.magic > 0xAA) nextState.current_func = E;
	else if(nextState.magic <= 0x7F) nextState.current_func = A;
	else nextState.current_func = C;

	try_push(nextState, state, ch);
}

void path_e(const STATE& state, unsigned char ch)
{
	if(state.path_count[E] > 2) return;
	STATE nextState = state;
	nextState.path_count[E]++;

	if(!(ch % 0x25 & 0xFF))
	{
		nextState.current_func = A;
		nextState.magic = state.magic - ch;
	}
	else
	{
		nextState.current_func = B;
		nextState.magic = state.magic - 1;
	}

	try_push(nextState, state, ch);
}

void path_f(const STATE& state, unsigned char ch)
{
	if(state.path_count[F] > 1) return;
	STATE nextState = state;
	nextState.path_count[F]++;

	if(ch != 2 && ch != 3) return;
	if(ch == 2)
	{
		if(state.magic <= 41)
		{
			nextState.magic = state.magic * 6;
		}
		else
		{
			nextState.magic = state.magic % 76 ? state.magic / 7 : 0;
		}
		nextState.current_func = E;
	}
	else if(ch == 3)
	{
		nextState.magic = state.magic - 1;
		nextState.current_func = F;
	}

	try_push(nextState, state, ch);
}

int main(void)
{
	STATE initial;
	memset(initial.path_count,0,sizeof(initial.path_count));
	initial.magic = 0x6B6C6565;
	initial.current_func = 0; // path_a
	q.push(initial);

	while(!q.empty())
	{
		STATE state = q.front(); q.pop();
		for(int i = 1;i < 256;i++)
		{
			if(i == '\n') continue;
			switch(state.current_func)
			{
			case A: path_a(state, i); break; 
			case B: path_b(state, i); break; 
			case C: path_c(state, i); break; 
			case D: path_d(state, i); break; 
			case E: path_e(state, i); break; 
			case F: path_f(state, i); break; 
			}
		}
	}
	puts("[-] Looks like no solution found. :(");
	return 0;
}