how to encrypt/decrypt
I need to encrypt/decrypt a set of numbers such as '1234'. The next stept to encrypting this number set is to ad '7' to each of the charaters ex = 1(becomes 8), 2(becomes 9), 3(becomes 0) and 4(becomes 1). Now, the addition part isn't causing me headaches yet, but how to pull the 1, 2,3, & the 4 out and add the 7 to them. Can someone show me how this works. Without running the code, it took me all of 15 seconds to realize that 1234 + 7777 wasn't what I wanted.
Thanks
BitWise
Last edited by bitWise; 10-13-2001 at 12:40 PM.
Do you want to get these numbers (1234) from the user? This is how you would do this:
This puts each value into the array.Code:char string[20]; int value[4]; fgets(string, sizeof(string), stdin); sscanf(string, "%d%d%d%d", &value[0], &value[1], &value[2], &value[3]);
Hi
You could try storing your numbers as a string - the general way of encryption.
Code:char numbers[5] = "1234"; char encrypt[5]; int i; for(i = 0; i < 5; i++) encrypt[i] = numbers[i] + 7; puts(encrypt); /*show encrypted numbers*/
Last edited by bigtamscot; 10-13-2001 at 12:30 PM.
hoping to be certified (programming in c)
here's the news - I'm officially certified.
That won't quite work, as '9' + 7 is not '6' as desired.
This, I think, will work.
try this:
Note, you can condense a lot of these steps(you can do it in 3 lines), but it's clearer written like this.Code:int temp, int exp = 0, int encrypted = 0, int normal; //set normal to the val to be encrypted. while(normal > 0){ temp = normal % 10; // gets the last digit of normal temp += 7; //adds 7 temp = temp % 10; //does wraparound such that 10 = 0, 11 = 1, etc. encrypted += temp * pow(10,exp); // puts this digit in its appropriate place, exp ++; //now, we want to do the next digit, so increase the exponent, normal /= 10; //shift all the digits down, discarding the lowest which we've already encrypted. }
