vegener

 Wegener

#include<stdio.h>

#include<string.h>

int main(){

    char msg[] = "THECRAZYPROGRAMMER";

    char key[] = "HELLO";

    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;

}