decryption problem!!

#1
s7s

Posted 23 June 2007 - 11:42 AM

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5 posts

Hello programmers:)

in fact i have a problem with my decrypting code !!

the encryption works fine with the APPLY_M function but when i do the reverse for the decription (APPLY_M_Reverse) it show wrong result !!

something missing or the order of things is not right..??

i need help plzzz

this is my code:

#include <stdio.h> 

typedef unsigned char uint8;

// Mixing function constant C

#define CSC_C00 0xb7

#define CSC_C01 0xe1

#define CSC_C02 0x51

#define CSC_C03 0x62

#define CSC_C04 0x8a

#define CSC_C05 0xed

#define CSC_C06 0x2a

#define CSC_C07 0x6a

// Mixing function constant C prime

#define CSC_C10 0xbf

#define CSC_C11 0x71

#define CSC_C12 0x58

#define CSC_C13 0x80

#define CSC_C14 0x9c

#define CSC_C15 0xf4

#define CSC_C16 0xf3

#define CSC_C17 0xc7


// P: the permutation table
uint8 tbp[256]={

		0x29,0x0d,0x61,0x40,0x9c,0xeb,0x9e,0x8f,

		0x1f,0x85,0x5f,0x58,0x5b,0x01,0x39,0x86,

		0x97,0x2e,0xd7,0xd6,0x35,0xae,0x17,0x16,

		0x21,0xb6,0x69,0x4e,0xa5,0x72,0x87,0x08,

		0x3c,0x18,0xe6,0xe7,0xfa,0xad,0xb8,0x89,

		0xb7,0x00,0xf7,0x6f,0x73,0x84,0x11,0x63,

		0x3f,0x96,0x7f,0x6e,0xbf,0x14,0x9d,0xac,

		0xa4,0x0e,0x7e,0xf6,0x20,0x4a,0x62,0x30,

		0x03,0xc5,0x4b,0x5a,0x46,0xa3,0x44,0x65,

		0x7d,0x4d,0x3d,0x42,0x79,0x49,0x1b,0x5c,

		0xf5,0x6c,0xb5,0x94,0x54,0xff,0x56,0x57,

		0x0b,0xf4,0x43,0x0c,0x4f,0x70,0x6d,0x0a,

		0xe4,0x02,0x3e,0x2f,0xa2,0x47,0xe0,0xc1,

		0xd5,0x1a,0x95,0xa7,0x51,0x5e,0x33,0x2b,

		0x5d,0xd4,0x1d,0x2c,0xee,0x75,0xec,0xdd,

		0x7c,0x4c,0xa6,0xb4,0x78,0x48,0x3a,0x32,

		0x98,0xaf,0xc0,0xe1,0x2d,0x09,0x0f,0x1e,

		0xb9,0x27,0x8a,0xe9,0xbd,0xe3,0x9f,0x07,

		0xb1,0xea,0x92,0x93,0x53,0x6a,0x31,0x10,

		0x80,0xf2,0xd8,0x9b,0x04,0x36,0x06,0x8e,

		0xbe,0xa9,0x64,0x45,0x38,0x1c,0x7a,0x6b,

		0xf3,0xa1,0xf0,0xcd,0x37,0x25,0x15,0x81,

		0xfb,0x90,0xe8,0xd9,0x7b,0x52,0x19,0x28,

		0x26,0x88,0xfc,0xd1,0xe2,0x8c,0xa0,0x34,

		0x82,0x67,0xda,0xcb,0xc7,0x41,0xe5,0xc4,

		0xc8,0xef,0xdb,0xc3,0xcc,0xab,0xce,0xed,

		0xd0,0xbb,0xd3,0xd2,0x71,0x68,0x13,0x12,

		0x9a,0xb3,0xc2,0xca,0xde,0x77,0xdc,0xdf,

		0x66,0x83,0xbc,0x8d,0x60,0xc6,0x22,0x23,

		0xb2,0x8b,0x91,0x05,0x76,0xcf,0x74,0xc9,

		0xaa,0xf1,0x99,0xa8,0x59,0x50,0x3b,0x2a,

		0xfe,0xf9,0x24,0xb0,0xba,0xfd,0xf8,0x55,

		};

// The Message
uint8 m[8] = {0x01,0x23,0x45,0x67,0x89,0xab,0xcd,0xef};

// The 9 keys
uint8 k[72] = {
		0x45,0xfd,0x13,0x7a,0x4e,0xdf,0x9e,0xc4,
		0x1d,0xd4,0x3f,0x03,0xe6,0xf7,0x56,0x4c,
		0xeb,0xe2,0x67,0x56,0xde,0x99,0x37,0xc7,
		0x96,0x17,0x04,0xe9,0x45,0xba,0xd4,0xfb,
		0x0b,0x60,0xdf,0xe9,0xef,0xf4,0x73,0xd4,
		0x76,0xd3,0xe7,0xcf,0x52,0xc4,0x66,0xcf,
		0x75,0xec,0x8c,0xef,0x76,0x7d,0x3a,0x0d,
		0x82,0xda,0x33,0x37,0xb5,0x98,0xfd,0x6d,
		0xfb,0xd8,0x20,0xda,0x8d,0xc8,0xaf,0x8c
		};

void APPLY_M(uint8 cl, uint8 cr, uint8 adl, uint8 adr)
{

	uint8 tmpx,tmprx,tmpy;

	tmpx=m[adl]^cl; 


	tmprx=(tmpx<<1)^(tmpx>>7); 


	tmpy=m[adr]^cr; 


	// yl
	m[adl]=tbp[(tmprx&0x55)^tmpx^tmpy]; 

	// yr

	m[adr]=tbp[tmprx^tmpy];


}

void APPLY_M_Reverse(uint8 cl, uint8 cr, uint8 adl, uint8 adr)
{

	uint8 tmpx,tmprx,tmpy,P, tmprP,rxl;

	tmpx=m[adl]^cl; 


	tmprx=(tmpx<<1)^(tmpx>>7); 


	tmpy=m[adr]^cr; 


	// xl
	P = tbp[tmpx]^tbp[tmpy];
	tmprP = (P<<1)^(P>>7);
	m[adl]=(tmprP&0xaa)^P;
	
	// xr
	rxl = (m[adl]<<1)^(m[adl]>>7);

	m[adr]=rxl^tbp[tmpy];

	

}
void enc_csc(uint8 m[8],uint8 k[72]) 
{

	int i,j;
	for(i=0;i<8;i++) 
	{
		printf(" m%d = ",i);
		for(j=0;j<8;j++) printf("%x",m[j]);
		printf(" \n");
	
		// mix with the first 8 keys, one key at each round
		APPLY_M(k[0+8*i],k[1+8*i],0,1);

		APPLY_M(k[2+8*i],k[3+8*i],2,3);

		APPLY_M(k[4+8*i],k[5+8*i],4,5);

		APPLY_M(k[6+8*i],k[7+8*i],6,7);

	
		// mix with the mixing function constant c
		APPLY_M(CSC_C00,CSC_C01,0,2);

		APPLY_M(CSC_C02,CSC_C03,4,6);

		APPLY_M(CSC_C04,CSC_C05,1,3);

		APPLY_M(CSC_C06,CSC_C07,5,7);

	
		// mix with the mixing function constant c'
		APPLY_M(CSC_C10,CSC_C11,0,4);

		APPLY_M(CSC_C12,CSC_C13,1,5);

		APPLY_M(CSC_C14,CSC_C15,2,6);

		APPLY_M(CSC_C16,CSC_C17,3,7);
	

	}
	printf(" m%d = ",i);
	for(i=0;i<8;i++) 
	printf("%x",m[i]);
	printf(" \n");
	
	// XOR with the key

	for(i=0;i<8;i++) m[i]^=k[64+i];


}

void dec_csc(uint8 m[8],uint8 k[72]) 
{

	int i,j;
	// XOR with the key

	for(i=0;i<8;i++) m[i]^=k[64+i];

	printf(" m%d = ",i);
	for(i=0;i<8;i++) 
	printf("%x",m[i]);
	printf(" \n");
	
	for(i=7;i>=0;i--) 
	{
		// mix with the mixing function constant c'
		APPLY_M_Reverse(CSC_C10,CSC_C11,0,4);

		APPLY_M_Reverse(CSC_C12,CSC_C13,1,5);

		APPLY_M_Reverse(CSC_C14,CSC_C15,2,6);

		APPLY_M_Reverse(CSC_C16,CSC_C17,3,7);
	
		// mix with the mixing function constant c
		APPLY_M_Reverse(CSC_C00,CSC_C01,0,2);

		APPLY_M_Reverse(CSC_C02,CSC_C03,4,6);

		APPLY_M_Reverse(CSC_C04,CSC_C05,1,3);

		APPLY_M_Reverse(CSC_C06,CSC_C07,5,7);
		
		// mix with the first 8 keys, one key at each round
		APPLY_M_Reverse(k[0+8*i],k[1+8*i],0,1);

		APPLY_M_Reverse(k[2+8*i],k[3+8*i],2,3);

		APPLY_M_Reverse(k[4+8*i],k[5+8*i],4,5);

		APPLY_M_Reverse(k[6+8*i],k[7+8*i],6,7);

	
		printf(" m%d = ",i);
		for(j=0;j<8;j++) printf("%x",m[j]);
		printf(" \n");

	}

}
int main()
{
	int j,i;
	//uint8* finalkey;

//	for(j=0;j<8;j++)
//	{
		enc_csc(m,k);
		
		printf("\n The ciphertext is: ");
		for(i=0;i<8;i++)
		{
			printf("%x",m[i]);			
		}
		printf("\n");
//		m[j]= m[j]+1;
		
//	}

//	for(j=0;j<8;j++)
//	{
		dec_csc(m,k);
		
		printf("\n The decrypted ciphertext is: ");
		for(i=0;i<8;i++)
		{
			printf("%x",m[i]);
		}
		printf("\n");
//		m[j]= m[j]-1;
		
//	}
	return 0;
}

am sorry for bothering ,, but plzzzzzz help me:(

regard,
s7s

#2
v0id

Posted 23 June 2007 - 12:39 PM

Retired

Members
2,936 posts

What is wrong? Doesn't it compile, do you get warnings, is it wrong output, and so on. Please specify it a bit.

At the moment I don't have much time, but I'll maybe take a deeper look at your code tomorrow. I don't say I can help you, because I'm not the best in encryption and decryption, but I'll give it a try. But first of all; try reading what I wrote in the top of this post.

#3
s7s

Posted 23 June 2007 - 01:22 PM

Newbie

Members
5 posts

it compiles , but it give me wrong result not as wht it should be!!

for example, when i run it ,
for the first part :
it should print the m[i] from 0 to 8
then print the cipher
and this part is correct till now..

but for the second part (decryption)
it should print back the above sequence in reverse :
m[i] from 8 to 0 and then the plain text

but it gives me m[8] right and the other is wrong

so ,, i hope i can get a help!! plzzzzzzzzzz
i need to have it work before monday morning:(

#4
s7s

Posted 24 June 2007 - 03:17 AM

Newbie

Members
5 posts

where are ya people !!!
someone help me ,plllzzzz!!!

i wish i can get a help before tomorrow ,,:( :(

#5
WingedPanther

Posted 25 June 2007 - 08:07 AM

A spammer's worst nightmare

Moderators
16,831 posts

If you could give us a clue as to which algorithm you are implementing, that might help. Given that you are using an unknown algorithm, it will be difficult to help you determine where you are going wrong.

Programming is a branch of mathematics.
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#6
s7s

Posted 26 June 2007 - 04:17 AM

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Members
5 posts

WingedPanther said:

am using the CS_Cipher , the encryption function with the help of APPLY_M would do the encryption process of a 64 bit plaintext and a key of 128 bit size. for the decryption the APPLY_M_Reverse() is used to do the opposit of the encryption process.

i guess my problem is with the order of doing things in the APPLY_M_Reverse it should be exactly the opposit of the APPLY_M() ..

i hope this would be more clearer:)

am trying to solve the problem by myself and nevermind if someone may help me..

kind regard,

s7s ..

#7
WingedPanther

Posted 26 June 2007 - 08:25 AM

A spammer's worst nightmare

Moderators
16,831 posts

A brief Google search failed to turn up an algorithm. There are a couple things I would check, however.
1) Make sure that your encoding is producing the correct result. Since it was part of a contest submitted to the federal government, there should be samples of what the encoded string should be for various unencoded strings.
2) Make sure you are actually reversing the process correctly. It's amazingly easy to screw up inverting a function (having done so a few times myself).

Programming is a branch of mathematics.
My CodeCall Blog | My Personal Blog