Autoblog de blog.rom1v.com

Un collègue m’a envoyé récemment le lien vers ce challenge, utilisé pour recruter chez NERD (que je ne connais pas).

Je vous le partage car je l’ai trouvé très intéressant. Le but est de trouver un input qui donne l’output attendu.

Pour info, entre le moment où j’ai eu connaissance du problème et le moment où je l’ai résolu, il s’est écoulé 6 jours. Je n’ai pas travaillé dessus à plein temps, mais ne comptez pas le résoudre en 20 minutes

Je ne publie ni ma réponse au résultat attendu, ni les explications (ce serait incorrect vis-à-vis des auteurs du challenge). Je fournis par contre à la fin l’input qui donne comme output mon e-mail, ce qui suffit à prouver que j’ai résolu le problème.

Amusez-vous bien !

#include <string.h>

typedef unsigned char u8;
typedef unsigned int u32;

u8 confusion[512]={
0xac,0xd1,0x25,0x94,0x1f,0xb3,0x33,0x28,0x7c,0x2b,0x17,0xbc,0xf6,0xb0,0x55,0x5d,
0x8f,0xd2,0x48,0xd4,0xd3,0x78,0x62,0x1a,0x02,0xf2,0x01,0xc9,0xaa,0xf0,0x83,0x71,
0x72,0x4b,0x6a,0xe8,0xe9,0x42,0xc0,0x53,0x63,0x66,0x13,0x4a,0xc1,0x85,0xcf,0x0c,
0x24,0x76,0xa5,0x6e,0xd7,0xa1,0xec,0xc6,0x04,0xc2,0xa2,0x5c,0x81,0x92,0x6c,0xda,
0xc6,0x86,0xba,0x4d,0x39,0xa0,0x0e,0x8c,0x8a,0xd0,0xfe,0x59,0x96,0x49,0xe6,0xea,
0x69,0x30,0x52,0x1c,0xe0,0xb2,0x05,0x9b,0x10,0x03,0xa8,0x64,0x51,0x97,0x02,0x09,
0x8e,0xad,0xf7,0x36,0x47,0xab,0xce,0x7f,0x56,0xca,0x00,0xe3,0xed,0xf1,0x38,0xd8,
0x26,0x1c,0xdc,0x35,0x91,0x43,0x2c,0x74,0xb4,0x61,0x9d,0x5e,0xe9,0x4c,0xbf,0x77,
0x16,0x1e,0x21,0x1d,0x2d,0xa9,0x95,0xb8,0xc3,0x8d,0xf8,0xdb,0x34,0xe1,0x84,0xd6,
0x0b,0x23,0x4e,0xff,0x3c,0x54,0xa7,0x78,0xa4,0x89,0x33,0x6d,0xfb,0x79,0x27,0xc4,
0xf9,0x40,0x41,0xdf,0xc5,0x82,0x93,0xdd,0xa6,0xef,0xcd,0x8d,0xa3,0xae,0x7a,0xb6,
0x2f,0xfd,0xbd,0xe5,0x98,0x66,0xf3,0x4f,0x57,0x88,0x90,0x9c,0x0a,0x50,0xe7,0x15,
0x7b,0x58,0xbc,0x07,0x68,0x3a,0x5f,0xee,0x32,0x9f,0xeb,0xcc,0x18,0x8b,0xe2,0x57,
0xb7,0x49,0x37,0xde,0xf5,0x99,0x67,0x5b,0x3b,0xbb,0x3d,0xb5,0x2d,0x19,0x2e,0x0d,
0x93,0xfc,0x7e,0x06,0x08,0xbe,0x3f,0xd9,0x2a,0x70,0x9a,0xc8,0x7d,0xd8,0x46,0x65,
0x22,0xf4,0xb9,0xa2,0x6f,0x12,0x1b,0x14,0x45,0xc7,0x87,0x31,0x60,0x29,0xf7,0x73,
0x2c,0x97,0x72,0xcd,0x89,0xa6,0x88,0x4c,0xe8,0x83,0xeb,0x59,0xca,0x50,0x3f,0x27,
0x4e,0xae,0x43,0xd5,0x6e,0xd0,0x99,0x7b,0x7c,0x40,0x0c,0x52,0x86,0xc1,0x46,0x12,
0x5a,0x28,0xa8,0xbb,0xcb,0xf0,0x11,0x95,0x26,0x0d,0x34,0x66,0x22,0x18,0x6f,0x51,
0x9b,0x3b,0xda,0xec,0x5e,0x00,0x2a,0xf5,0x8f,0x61,0xba,0x96,0xb3,0xd1,0x30,0xdc,
0x33,0x75,0xe9,0x6d,0xc8,0xa1,0x3a,0x3e,0x5f,0x9d,0xfd,0xa9,0x31,0x9f,0xaa,0x85,
0x2f,0x92,0xaf,0x67,0x78,0xa5,0xab,0x03,0x21,0x4f,0xb9,0xad,0xfe,0xf3,0x42,0xfc,
0x17,0xd7,0xee,0xa3,0xd8,0x80,0x14,0x2e,0xa0,0x47,0x55,0xc4,0xff,0xe5,0x13,0x3f,
0x81,0xb6,0x7a,0x94,0xd0,0xb5,0x54,0xbf,0x91,0xa7,0x37,0xf1,0x6b,0xc9,0x1b,0xb1,
0x3c,0xb6,0xd9,0x32,0x24,0x8d,0xf2,0x82,0xb4,0xf9,0xdb,0x7d,0x44,0xfb,0x1e,0xd4,
0xea,0x5d,0x35,0x69,0x23,0x71,0x57,0x01,0x06,0xe4,0x55,0x9a,0xa4,0x58,0x56,0xc7,
0x4a,0x8c,0x8a,0xd6,0x6a,0x49,0x70,0xc5,0x8e,0x0a,0x62,0xdc,0x29,0x4b,0x42,0x41,
0xcb,0x2b,0xb7,0xce,0x08,0xa1,0x76,0x1d,0x1a,0xb8,0xe3,0xcc,0x7e,0x48,0x20,0xe6,
0xf8,0x45,0x93,0xde,0xc3,0x63,0x0f,0xb0,0xac,0x5c,0xba,0xdf,0x07,0x77,0xe7,0x4e,
0x1f,0x28,0x10,0x6c,0x59,0xd3,0xdd,0x2d,0x65,0x39,0xb2,0x74,0x84,0x3d,0xf4,0xbd,
0xc7,0x79,0x60,0x0b,0x4d,0x33,0x36,0x25,0xbc,0xe0,0x09,0xcf,0x5b,0xe2,0x38,0x9e,
0xc0,0xef,0xd2,0x16,0x05,0xbe,0x53,0xf7,0xc2,0xc6,0xa2,0x24,0x98,0x1c,0xad,0x04};

u32 diffusion[32]={
0xf26cb481,0x16a5dc92,0x3c5ba924,0x79b65248,0x2fc64b18,0x615acd29,0xc3b59a42,0x976b2584,
0x6cf281b4,0xa51692dc,0x5b3c24a9,0xb6794852,0xc62f184b,0x5a6129cd,0xb5c3429a,0x6b978425,
0xb481f26c,0xdc9216a5,0xa9243c5b,0x524879b6,0x4b182fc6,0xcd29615a,0x9a42c3b5,0x2584976b,
0x81b46cf2,0x92dca516,0x24a95b3c,0x4852b679,0x184bc62f,0x29cd5a61,0x429ab5c3,0x84256b97};

u8 input[32]={
//change only this :
0x66,0xd5,0x4e,0x28,0x5f,0xff,0x6b,0x53,0xac,0x3b,0x34,0x14,0xb5,0x3c,0xb2,0xc6,
0xa4,0x85,0x1e,0x0d,0x86,0xc7,0x4f,0xba,0x75,0x5e,0xcb,0xc3,0x6e,0x48,0x79,0x8f
//
};

void Forward(u8 c[32],u8 d[32],u8 s[512],u32 p[32])
{
	for(u32 i=0;i<256;i++)
	{
		for(u8 j=0;j<32;j++)
		{
			d[j]=s[c[j]];
			c[j]=0;
		}

		for(u8 j=0;j<32;j++)
			for(u8 k=0;k<32;k++)
				c[j]^=d[k]*((p[j]>>k)&1);
	}
	for(u8 i=0;i<16;i++)
		d[i]=s[c[i*2]]^s[c[i*2+1]+256];
}

int main(int argc, char* argv[])
{
	u8 target[]="Hire me!!!!!!!!";
	u8 output[32];

	Forward(input,output,confusion,diffusion);

	return memcmp(output,target,16); // => contact jobs(at)nerd.nintendo.com
}

Ma preuve de solution :

diff --git a/HireMe.cpp b/HireMe.cpp
index ca94719..8374683 100644
--- a/HireMe.cpp
+++ b/HireMe.cpp
@@ -45,8 +45,8 @@ u32 diffusion[32]={
 
 u8 input[32]={
 //change only this :
-0x66,0xd5,0x4e,0x28,0x5f,0xff,0x6b,0x53,0xac,0x3b,0x34,0x14,0xb5,0x3c,0xb2,0xc6,
-0xa4,0x85,0x1e,0x0d,0x86,0xc7,0x4f,0xba,0x75,0x5e,0xcb,0xc3,0x6e,0x48,0x79,0x8f
+0x82,0x69,0xd7,0x3c,0xd7,0x58,0xd7,0x0d,0x22,0x46,0x58,0x22,0x22,0x69,0x22,0x77,
+0x77,0xd7,0x77,0xe6,0xf8,0x22,0xd7,0x58,0x9c,0x58,0x3c,0xf8,0xf8,0x22,0x58,0x13
 //
 };
 
@@ -70,7 +70,7 @@ void Forward(u8 c[32],u8 d[32],u8 s[512],u32 p[32])
 
 int main(int argc, char* argv[])
 {
-	u8 target[]="Hire me!!!!!!!!";
+	u8 target[]="[rom@rom1v.com]";
 	u8 output[32];
 
 	Forward(input,output,confusion,diffusion);