Question

You are required to write a program that will emulate the One Time Pad implementing the Vernam cipher. Your program should allow one side to produce a one-time pad randomly using a specific seed value that will call a pseudo-random number generator function a number of times (say 16 times to generate 16 characters) to produce the one-time pad. Thus, the program should read a text and encrypt it 16 characters at a time using the produced pad, then send it to the receiver side for decryption while adding a sequence number. The receiver should be able to produce the same pad, using the same seed for the pseudo-random number generator function. For any subsequent message to be sent the seed has to be changed. You need to devise a mechanism (using a hash function or a pattern, etc.) that will allow send and receiver to synchronize the generation of the one-time pad each time for each block/message sent.

You may refer to the following link for an example of how the one-time pad is used with the Vernam Cipher.

https://www.geeksforgeeks.org/vernam-cipher-in-cryptography/

You should do this as groups of two students. You may refer to some reference code from the literature but not to copy-paste other people assignments. If you do, you will be penalized.

You should produce a report with the source code and snapshots of execution + source code in Electronic format (as a project). You may use either C, C++ or Java for this programming task.

Answer 1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

#include<stdio.h> #include<string.h> int main(){     char msg[100],key[100]; scanf("%s",msg); scanf("%s",key);     int msgLen = strlen(msg), keyLen = strlen(key), i, j;     char newKey[msgLen], encryptedMsg[msgLen], decryptedMsg[msgLen];     //generating new key     for(i = 0, j = 0; i < msgLen; ++i, ++j){         if(j == keyLen)             j = 0;         newKey[i] = key[j];     }     newKey[i] = '\0';     //encryption     for(i = 0; i < msgLen; ++i)         encryptedMsg[i] = ((msg[i] + newKey[i]) % 26) + 'A';     encryptedMsg[i] = '\0';     //decryption     for(i = 0; i < msgLen; ++i)         decryptedMsg[i] = (((encryptedMsg[i] - newKey[i]) + 26) % 26) + 'A';     decryptedMsg[i] = '\0';     printf("Original Message: %s", msg);     printf("\nKey: %s", key);     printf("\nNew Generated Key: %s", newKey);     printf("\nEncrypted Message: %s", encryptedMsg);     printf("\nDecrypted Message: %s", decryptedMsg); return 0; }