codegate 2015 - good crypto - solve.cpp

/* C++ */
#define NEEDSOL "\xff\x7b\x94\x89\x53\xac"
//#define NEEDSOL "\x2b\x0e\x60\xef\xf9\xca"

char s[20]="";
char hashxor[4];
int len = 10;
int lastlen = len-4;
char targetHash[10]="\x6b\x76\x12";
char CS[] = "abcdefghijklmnopqrstuvwxyz";
int CSL_ = sizeof(CS)-1;
int CSL = CSL_;
long long nhash = 0;
void solve(int i){
	if(i==3){
		for(int j=0;j<i;j++) putchar(s[j]);putchar('*');putchar(';');fflush(stdout);
	}
	if(i==len){
		static unsigned char hash[20];
		s[i]=0;
		//printf("possible key %s | %02X:%02X:%02X\n",s,hashxor[0],hashxor[1],hashxor[2]);exit(0);
		nhash ++ ;
		sha1::calc(s, len, hash);
		if(!strncmp(NEEDSOL,(const char*)hash,6)){
			for(int i=0;i<len+3;i++) putchar(s[i]);
			printf("\n");
			exit(0);
		}
		return;
	}
	if(i>=lastlen && (i%4)!=3){
		s[i] = targetHash[i&3]^hashxor[i&3];
		if(((s[i]>='a')&&(s[i]<='z'))||((s[i]>='A')&&(s[i]<='Z')))
			solve(i+1);
	}else{
		for(int j=0;j<CSL;j++) s[i]=CS[j], hashxor[i&3]^=CS[j], solve(i+1), hashxor[i&3]^=CS[j];
	}
	return;
}

int main(int argc, char** argv){
	int start_index = 0;
	if(argc>1){
		printf("test %s\n",argv[1]);
		strcpy(s, argv[1]);
		start_index = strlen(s);
		for(int i=0;i<start_index;i++) hashxor[i&3]^=s[i];
	}
	solve(start_index);
}