MASM Program (using Visual Studios)

Can someone please help me with this? It is an example program to help us better understand the assembly language. However, I can not get mine to compile and I'm not sure what I am doing wrong. Thank you in advance.

The program should be implemented with a driver program that calls the RC4 key stream generation functions, encrypting hello World with a key of test.

RC4 is a stream cipher originally developed in 1987 by Ron Rivest of RSA Security [3]. Because of its simplicity and speed, it was used extensively for several applications and became the basis for the WEP standard used for wireless encryption. The basic concept is that a pseudo-random string of bytes is generated which is XORd with the plaintext to generate the cipher text.

Main:

Declare state array256 bytes.

Declare and initialize the key array key ={test}

Declare the output stream array 1024 bytes.

Declare plaintext character array ={Hello World} be certain to include the null terminator.

Declare the cypherText array at least 12 characters long initialized to 0.

Declare the plaintextOut array at least 12 characters long initialized to 0.

Declare and Initialize len=11

Declare and Initialize keylen=4

Call rc4Init passing (state, key, keylen)

Call rc4KeyGen(state, stream, len);

for (int i = 0; i < len; i++)

{

cypherText[i] = stream[i] xor plainText[i];

plainTextOut[i] = stream[i] xor cypherText[i];

printf("%02X %02X", stream[i], cypherText[i]);

Skip to a new line

}

print plainText and plainTextOut

return

To generate the random bytes, a permutation of all possible combinations of bytes is stored in a 256 element array known as the S array. Initialization of the S array uses a key of arbitrary length to shuffle the locations using the simple algorithm shown:

// Key Scheduling Algorithm

// Input: state - the state used to generate the keystream

// key - Key to use to initialize the state

// keylen - length of key in bytes

void rc4Init(unsigned char state[], unsigned char key[], int keylen)

{

int i, j = 0, t;

for (i = 0; i < 256; ++i)

state[i] = i;

for (i = 0; i < 256; ++i) {

j = (j + state[i] + key[i % keylen]) % 256;

t = state[i];

state[i] = state[j];

state[j] = t;

}

}

The result of this initialization is an array with values 0-255 in an arbitrary order based on the key. Once the S array has been initialized, an equally simple algorithm is used to generate as many pseudo-random bytes as necessary to encode the message.

// Pseudo-Random Generator Algorithm

// Input: state - the state used to generate the keystream

// out - Must be of at least "len" length

// len - number of bytes to generate

void rc4KeyGen(unsigned char state[], unsigned char out[], int len)

{

int i = 0, j = 0, x, t;

unsigned char key;

for (x = 0; x < len; ++x) {

i = (i + 1) % 256;

j = (j + state[i]) % 256;

t = state[i];

state[i] = state[j];

state[j] = t;

out[x] = state[(state[i] + state[j]) % 256];

}

}

Compile and run program test with the test case indicated above.

Example Output:

Welcome to pat programmer's RC4 stream cypher

cyphertext

00000048

000000EA

0000004B

0000007D

0000006F

0000000A

00000057

0000004A

00000072

00000022

00000039

Plaintext : Hello World

Plaintext Out: Hello World