void decode()
{
char line[1000];
long int index;
char decoding[] = {' ','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'
,'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'
,'0','1','2','3','4','5','6','7','8','9'
,',','.','!'};
FILE *fpRdRcvd,*fpWrRcvd;
fpRdRcvd = fopen("receivedTemp.txt","r");
if(fpRdRcvd==NULL){printf("Error opening file\n");exit(0);}
fpWrRcvd = fopen("ReceivedFile.txt","w");
if(fpWrRcvd==NULL){printf("Error opening write file\n");exit(0);}
if(fgets(line,sizeof(line),fpRdRcvd)==NULL)printf("Empty File\n");
fseek(fpRdRcvd,0,SEEK_SET);
while(fgets(line,sizeof(line),fpRdRcvd)!=NULL)
{
if(line[0]=='\n')fputs(line,fpWrRcvd);
else
{
index = atoi(line);
index = DecryptionAlgorithm(index,pvt_key);
fprintf(fpWrRcvd,"%c",decoding[index]);
}
}
/* fseeko(fpWrRcvd,-6,SEEK_END);
off_t position = ftello(fpWrRcvd);
ftruncate(fileno(fpWrRcvd), position);*/
fclose(fpRdRcvd);
fclose(fpWrRcvd);
}
/* Interaction with the server */
void Talk_to_server ( int cfd )
{
int cont;
int nbytes, status;
int src_addr, dest_addr;
char filename[25], id[10], pw[10];
Msg send_msg;
Msg recv_msg;
long int q, alpha, secret_key, public_key, private_key;
long int X_A, Y_A, Y_B;
FILE *fp;
dest_addr = inet_addr("DEFAULT_SERVER");
src_addr = inet_addr("192.168.1.245");
printf("\n\nRegistration Phase:\n\n");
printf("\nDo you want to register?(y:1/n:0)\t");
scanf("%d", &cont);
while(cont)
{
printf("\nEnter the ID:\t");
scanf("%s", id);
printf("\nEnter the Password:\t");
scanf("%s", pw);
send_msg.hdr.opcode = REGISTER;
send_msg.hdr.src_addr = src_addr;
send_msg.hdr.dest_addr = dest_addr;
strcpy(send_msg.m.auth.id, id);
strcpy(send_msg.m.auth.pw, pw);
/* send the user's response to the server */
status = send(cfd, &send_msg, sizeof(Msg), 0);
if (status == -1)
{
fprintf(stderr, "*** Server error: unable to send\n");
return;
}
printf("\nContinue with registration?(y:1/n:0)\t");
scanf("%d", &cont);
}
printf("\n\nLogin Phase:\n");
printf("\nEnter the ID:\t");
scanf("%s", id);
printf("\nEnter the Password:\t");
scanf("%s", pw);
send_msg.hdr.opcode = LOGINREQ;
send_msg.hdr.src_addr = src_addr;
send_msg.hdr.dest_addr = dest_addr;
strcpy(send_msg.m.auth.id, id);
strcpy(send_msg.m.auth.pw, pw);
/* send the user's response to the server */
status = send(cfd, &send_msg, sizeof(Msg), 0);
if (status == -1)
{
fprintf(stderr, "*** Server error: unable to send\n");
return;
}
/* Wait for responses from the server (Bob, User B) */
while ( 1 )
{
/* receive messages from server */
nbytes = recv(cfd, &recv_msg, sizeof(Msg), 0);
if (nbytes == -1)
{
fprintf(stderr, "*** Client error: unable to receive\n");
}
switch ( recv_msg.hdr.opcode )
{
case LOGINREP : /* Login Reply */
printf("\n\nMessage:: LOGINREP received from source (%d)\n", recv_msg.hdr.src_addr);
printf("%s\n", recv_msg.m.buf);
if( (strcmp(recv_msg.m.buf, "Wrong ID/Password!") == 0) )
{
exit(0) ;
}
else if( (strcmp(recv_msg.m.buf, "Authenticated!") == 0) )
{
send_msg.hdr.opcode = PUBKEY;
send_msg.hdr.src_addr = src_addr;
send_msg.hdr.dest_addr = dest_addr;
printf("\nKey Generaion has been started:\n\r");
KeyGeneration(&q, &alpha, &private_key, &public_key);
printf("Global public elements are q = %ld, alpha = %ld\n\r", q, alpha);
printf("Public Key for Alice (User A) is Y_A: %ld\n\r", public_key);
printf("Private key for Alice (User A) is X_A: %ld\n\r", private_key);
X_A = private_key;
Y_A = public_key;
/* send the public key to Bob */
printf("Sending the public key to Bob (User B)\n");
send_msg.m.dhpubkey.q = q; /* q */
send_msg.m.dhpubkey.g = alpha; /* alpha */
send_msg.m.dhpubkey.Y = Y_A; /* value of public key */
status = send(cfd, &send_msg, sizeof(Msg), 0);
if (status == -1)
{
fprintf(stderr, "*** Client error: unable to send\n");
return;
}
}
break;
case PUBKEY : /* Public key */
printf("\n\nMessage:: PUBKEY received from source (%d)\n", recv_msg.hdr.src_addr);
/* Compute the secret shared key based on public key received from Bob (User B) */
Y_B = recv_msg.m.dhpubkey.Y;
printf("Received public values from Bob are q = %ld, alpha = %ld, Y_B = %ld\n\r",
recv_msg.m.dhpubkey.q, recv_msg.m.dhpubkey.g, Y_B);
secret_key = ModPower(Y_B, X_A, q);
printf("Computed secret shared key by Alice (User A) is %ld\n\r", secret_key);
printf("\n\nEnter the file to be retrieved:\t");
scanf("%s", filename);
/* Send an acknowledgement to Bob that the secret key is computed */
send_msg.hdr.opcode = REQSERV;
send_msg.hdr.src_addr = src_addr;
send_msg.hdr.dest_addr = dest_addr;
strcpy(send_msg.m.buf, filename);
fp = fopen(filename, "w"); // append mode
fclose(fp);
status = send(cfd, &send_msg, sizeof(Msg), 0);
if (status == -1)
{
fprintf(stderr, "*** Client error: unable to send\n");
return;
}
break;
case ENCMSG : /* Encrypted msg */
printf("\n\nMessage:: ENCMSG received from source (%d)\n", recv_msg.hdr.src_addr);
printf("\nCiphertext received:\n\n%s\n", recv_msg.m.buf);
/* decrypt the ciphertext */
strcpy(buffer, recv_msg.m.buf);
DecryptionAlgorithm(buffer, secret_key);
printf("\nRecovered plaintext:\n\n%s\n", buffer);
char ch;
fp = fopen(filename, "a"); // append mode
if( fp == NULL )
{
perror("Error while opening the file.\n");
exit(EXIT_FAILURE);
}
fwrite(buffer, 1, strlen(buffer), fp);
fclose(fp);
printf("Written to file.\n");
break;
case REQCOM : /* Request Complete */
printf("\n\nMessage:: REQCOM received from source (%d)\n", recv_msg.hdr.src_addr);
printf("\n%s\n", recv_msg.m.buf);
printf("\nDisconnecting from server!\n");
send_msg.hdr.opcode = DISCONNECT;
send_msg.hdr.src_addr = src_addr;
send_msg.hdr.dest_addr = dest_addr;
strcpy(send_msg.m.buf, "Disconnect...");
status = send(cfd, &send_msg, sizeof(Msg), 0);
if (status == -1)
{
fprintf(stderr, "*** Client error: unable to send\n");
return;
}
break;
case DISCONNECT :/* Disconnect */
printf("\n\nMessage:: DISCONNECT received from source (%d)\n", recv_msg.hdr.src_addr);
printf("%s\n", recv_msg.m.buf);
exit(0);
break;
}
}
}
/* Interaction with the server */
void Talk_to_server ( int cfd ,char* agrv_filename)
{
char str[STACK_SIZE],str_concat[STACK_SIZE];
int x, e;
FILE *fptr1;
key pub_key, pvt_key;
//char ch;
char buffer[MAX_LEN];
int nbytes, status;
int src_addr, dest_addr;
long int plaintext, ciphertext, deciphertext;
KeyGeneration(&pub_key, &pvt_key);
ReqMsg send_msg;
RepMsg recv_msg;
//key_public public_key;
// printf("\n Public Key of Alice is (n,e): (%ld , %ld)\n\r", pub_key.public_key.n, pub_key.public_key.e);
printf("\n Private key of Alice is (n,d): (%ld , %ld)\n\r", pvt_key.private_key.n,
pvt_key.private_key.d);
dest_addr = inet_addr(DEFAULT_SERVER);
src_addr = inet_addr("127.0.0.5");
printf("Sending the public_key to the server\n");
Msg msg;
msg.hdr.opcode=Pubkey;
msg.hdr.src_addr = src_addr;
msg.hdr.dest_addr = dest_addr;
msg.AllMsg.pubkey.n=pub_key.public_key.n;
msg.AllMsg.pubkey.e=pub_key.public_key.e;
int t_block=66,n_block=0;
while(t_block<pub_key.public_key.n)
{
t_block=66+t_block*100;
++n_block;
}
status = send(cfd, &msg, sizeof(Msg), 0);
if (status == -1) {
fprintf(stderr, "*** Server error: unable to send\n");
return;
}
/* send the request message REQ to the server */
printf("Sending the request message REQ to the server\n");
msg.hdr.opcode = REQ;
msg.hdr.src_addr = src_addr;
msg.hdr.dest_addr = dest_addr;
strcpy(msg.AllMsg.req.filename, agrv_filename);
//printf("here\n");
printf("File name is:- %s\n",msg.AllMsg.req.filename);
status = send(cfd, &msg, sizeof(Msg), 0);
if (status == -1) {
fprintf(stderr, "*** Server error: unable to send\n");
return;
}
//exit(0);
while (1) {
/* receive greetings from server */
nbytes = recv(cfd, &msg, sizeof(Msg), 0);
if (nbytes == -1) {
fprintf(stderr, "*** Client error: unable to receive\n");
}
switch ( msg.hdr.opcode ) {
case REP :
sprintf(str,"%ld",DecryptionAlgorithm(msg.AllMsg.rep.chyp,pvt_key));
if(strlen(str)%2==1)
{
strcpy(str_concat,"0");
strcat(str_concat,str);
strcpy(str,str_concat);
}
if(strlen(str)/(2*n_block)!=1)
{
strcpy(str_concat,"00");
strcat(str_concat,str);
strcpy(str,str_concat);
}
/*printf("\nsha1 is:");
int loop_print;
for (loop_print = 0; loop_print < SHA_DIGEST_LENGTH; ++loop_print)
{
printf("%u",msg.sha1_send[loop_print] );
}*/
//printf("final %s\n",str);
substitute_back(str);
//printf("sha1 for sub%s\n",string_sha1);
unsigned char digest[SHA_DIGEST_LENGTH];
memset(digest,'\0',SHA_DIGEST_LENGTH);
/*int x;
for (x= 0; x < strlen(string_sha1); ++x)
{
printf("string[%d]%c",x,string_sha1[x] );
}
printf("\n");*/
//printf("size : %d\nText : #%s#", strlen(string_sha1), string_sha1);
SHA1(string_sha1,strlen(string_sha1),digest);
int for_loop;
/* for (i=0; i < SHA_DIGEST_LENGTH; i++) {
sprintf((char*)&(buf[i*2]), "%02x", temp[i]);
}*/
for (for_loop = 0; for_loop < SHA_DIGEST_LENGTH; ++for_loop)
{
if(msg.sha1_send[for_loop]!=digest[for_loop])
{
msg.hdr.opcode=Disc;
msg.AllMsg.disconnect.status=1;
status = send(cfd, &msg, sizeof(Msg), 0);
if (status == -1) {
fprintf(stderr, "hi Server error: unable to send\n");
return;
}
}
}
memset(string_sha1,'\0',strlen(string_sha1));
//printf("\n");
//printf("substitute after %s\n", string_substitute);
//printf("plaintext : %ld\n",plain);
/* Check the status of REP message */
/* if (msg.AllMsg.r.status)
printf("Message REQ has received successfully by the server\n");
else
printf("Message REQ has NOT received successfully by the server\n");*/
break;
case REQCOM:
if(msg.AllMsg.reqcom.status==1)
{
msg.hdr.opcode=Disc;
msg.AllMsg.disconnect.status=1;
fptr1 = fopen(agrv_filename,"w");
if (fptr1 == NULL)
printf("Error in writing to the file\n");
fprintf(fptr1, "%s", string_substitute);
fclose(fptr1);
}
printf("file recived complted doing deciphertext opcode is Disconnect: %d\n", msg.hdr.opcode);
status = send(cfd, &msg, sizeof(Msg), 0);
if (status == -1) {
printf("Disconnect client opcode: %d\n", msg.hdr.opcode);
exit(0);
}
//exit(0);
break;
case Disc :
printf("Disconnect client opcode: %d\n", msg.hdr.opcode);
exit(0);
break;
default:
//printf("default\n");
printf("message received with opcode: %d\n", msg.hdr.opcode);
exit(0);
}
}
}
