Can you add rsa encryption and decryption to this program for both client and server. Its in C.

CLIENT

#include /* for printf() and fprintf() */ #include /* for socket(), connect(), sendto(), and recvfrom() */ #include /* for sockaddr_in and inet_addr() */ #include /* for atoi() and exit() */ #include /* for memset() */ #include /* for close() */

#define ECHOMAX 255 /* Longest string to echo */

void DieWithError(char *errorMessage); /* External error handling function */

int main(int argc, char *argv[]) { int sock; /* Socket descriptor */ struct sockaddr_in echoServAddr; /* Echo server address */ struct sockaddr_in fromAddr; /* Source address of echo */ unsigned short echoServPort; /* Echo server port */ unsigned int fromSize; /* In-out of address size for recvfrom() */ char *servIP; /* IP address of server */ char *echoString; /* String to send to echo server */ char echoBuffer[ECHOMAX+1]; /* Buffer for receiving echoed string */ int echoStringLen; /* Length of string to echo */ int respStringLen; /* Length of received response */ if ((argc < 3) || (argc > 4)) /* Test for correct number of arguments */ { fprintf(stderr,"Usage: %s [] ", argv[0]); exit(1); } servIP = argv[1]; /* First arg: server IP address (dotted quad) */ echoString = argv[2]; /* Second arg: string to echo */ if ((echoStringLen = strlen(echoString)) > ECHOMAX) /* Check input length */ DieWithError("Echo word too long"); if (argc == 4) echoServPort = atoi(argv[3]); /* Use given port, if any */ else echoServPort = 7; /* 7 is the well-known port for the echo service */ /* Create a datagram/UDP socket */ if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) DieWithError("socket() failed"); /* Construct the server address structure */ memset(&echoServAddr, 0, sizeof(echoServAddr)); /* Zero out structure */ echoServAddr.sin_family = AF_INET; /* Internet addr family */ echoServAddr.sin_addr.s_addr = inet_addr(servIP); /* Server IP address */ echoServAddr.sin_port = htons(echoServPort); /* Server port */ /* Send the string to the server */ if (sendto(sock, echoString, echoStringLen, 0, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr)) != echoStringLen) DieWithError("sendto() sent a different number of bytes than expected"); /* Recv a response */ fromSize = sizeof(fromAddr); if ((respStringLen = recvfrom(sock, echoBuffer, ECHOMAX, 0, (struct sockaddr *) &fromAddr, &fromSize)) != echoStringLen) DieWithError("recvfrom() failed"); if (echoServAddr.sin_addr.s_addr != fromAddr.sin_addr.s_addr) { fprintf(stderr,"Error: received a packet from unknown source. "); exit(1); } /* null-terminate the received data */ echoBuffer[respStringLen] = '\0'; printf("Received: %s ", echoBuffer); /* Print the echoed arg */ close(sock); exit(0); }

SERVER

#include /* for printf() and fprintf() */ #include /* for socket() and bind() */ #include /* for sockaddr_in and inet_ntoa() */ #include /* for atoi() and exit() */ #include /* for memset() */ #include /* for close() */

#define ECHOMAX 255 /* Longest string to echo */

void DieWithError(char *errorMessage); /* External error handling function */

int main(int argc, char *argv[]) { int sock; /* Socket */ struct sockaddr_in echoServAddr; /* Local address */ struct sockaddr_in echoClntAddr; /* Client address */ unsigned int cliAddrLen; /* Length of incoming message */ char echoBuffer[ECHOMAX]; /* Buffer for echo string */ unsigned short echoServPort; /* Server port */ int recvMsgSize; /* Size of received message */ if (argc != 2) /* Test for correct number of parameters */ { fprintf(stderr,"Usage: %s ", argv[0]); exit(1); } echoServPort = atoi(argv[1]); /* First arg: local port */ /* Create socket for sending/receiving datagrams */ if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) DieWithError("socket() failed"); /* Construct local address structure */ memset(&echoServAddr, 0, sizeof(echoServAddr)); /* Zero out structure */ echoServAddr.sin_family = AF_INET; /* Internet address family */ echoServAddr.sin_addr.s_addr = htonl(INADDR_ANY); /* Any incoming interface */ echoServAddr.sin_port = htons(echoServPort); /* Local port */ /* Bind to the local address */ if (bind(sock, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr)) < 0) DieWithError("bind() failed"); for (;;) /* Run forever */ { /* Set the size of the in-out parameter */ cliAddrLen = sizeof(echoClntAddr); /* Block until receive message from a client */ if ((recvMsgSize = recvfrom(sock, echoBuffer, ECHOMAX, 0, (struct sockaddr *) &echoClntAddr, &cliAddrLen)) < 0) DieWithError("recvfrom() failed"); printf("Handling client %s ", inet_ntoa(echoClntAddr.sin_addr)); /* Send received datagram back to the client */ if (sendto(sock, echoBuffer, recvMsgSize, 0, (struct sockaddr *) &echoClntAddr, sizeof(echoClntAddr)) != recvMsgSize) DieWithError("sendto() sent a different number of bytes than expected"); } /* NOT REACHED */ }