14
votes
Not able to understand what I need to do in pset2 (crack.c)
Just imagine one day you get a "hashed password" that could be used to log into your girlfriend's email, what will you do? Is it possible to log into the email with that "hashed password"? Of course, ...
- 241
6
votes
Accepted
Crack - launching and crypt function
crypt() is an encryption algorithm. It takes a plaintext string (a user password), and encrypts it, so that it can be stored in a file.
char *crypt(const char *key, const char *salt)
The key ...
- 812
6
votes
Accepted
PSET2: CRACK vs POINTERS
Your problem is that letters[i] is a char, but the crypt() function expects a char * (string) as its first argument. So what you really want to do is pass a string with a single character, not a ...
- 7,396
4
votes
C's DES based crypt function?
Whether crypt function uses DES or MD5-based algorithm is determined by what salt argument you pass to it. If the salt you pass consists of 2 alphanumeric characters, the function uses DES algorithm. ...
- 117
4
votes
Accepted
pset2: Crack takes a lot of time
Answered by an instructor on reddit.
here:https://www.reddit.com/r/cs50/comments/9o3eg8/pset2_crack_is_taking_a_lot_of_time/
- 53
3
votes
Accepted
pset2 crack segmentation fault
string is defined in cs50.h as an alias for char *.
string s = "word"; declares a pointer to char named s and lets it point to the string constant "word".
You could use an array instead, like char s[...
- 21k
3
votes
Accepted
Easiest method to organize code
You went down the rabbit hole with this pset. You chose the wrong path at the fork on the road. Just think for a minute how mush you will have to change, if instead of 5 letters which is the current ...
- 7,396
3
votes
Accepted
pset2 crack - values are equal but the program claims equality is false
You should use strcmp, not "==" when comparing two strings in c. The strcmp function, included in string.h takes in two parameters, your two strings, and outputs 0 if the strings are equal. If you ...
- 182
3
votes
Accepted
CS50 crack confusion?
Your problem is probably because of this line:
char salt[2] = "50";
If you recall, you have to end a string with an additional character, the null zero '\0', so technically salt is 3 characters long....
- 7,396
2
votes
Accepted
Crypt() includes and compiling
It will work when constructed as in the man page. From man feature_test_macros:
NOTE: In order to be effective, a feature test macro must be defined before including any header files. This can ...
- 28.6k
2
votes
Accepted
About the 'crack.c' part of the second hacker edition pset, what is really expected from us? (and a part about submitting)
So I'm wondering if submitting a program that would work but can't be actually tested is okay and is what is expected from us
It is expected of you to find all the plaintext passwords of the hashed ...
- 7,396
2
votes
Accepted
Trying to Increment Characters in a String
One way would be to interpret characters 'a' to 'z' as digits in a number with base 26, start at "aaaa" (representing 0), and then adding 1 to the last string. Add or subtract 'a' for conversion ...
- 21k
2
votes
Accepted
Passing string literal to a function: segmentation fault
There's a couple of things that I can see won't work:
string unhashed = capsPattern(wordsArray[i], "1011");
I can't see how this will work as you're expecting, as wordsArray[i] is just character i ...
- 1,122
2
votes
Accepted
Crack -- why does my code only work on the 4 character passwords?
This is because when you reach the innermost loop for the first time, your array is already four characters. Now for all the permutations you will have four characters in the array. This is the reason ...
- 550
2
votes
I solved crack, but have a shallow understanding of the techniques used
In C a string name is just a pointer to the actual string located somewhere
in memory ending with a NULL character. So when you use the "==" operator to
check it's equality you are basically ...
- 550
2
votes
Accepted
Use of crypt function - comparing output
Strings in C are pointers to char, pointing to the first character in the string, so the value you compared is a memory address. To compare strings by content rather than by address, use the strcmp ...
- 21k
2
votes
PSet 2: Crack - Faster Methods?
I have used recursion, wrapped inside one loop for the number of digits. Which I think is the same approach mentioned by User20025. The recursion concept is that a 3 letter password is 1 letter plus a ...
- 21
2
votes
pset2 crack segmentation fault
I believe this has something to do with the <= in your for loop. You would iterate 53 instead of 52 times, allowing s[0] = alpha [53] which would be out of range thus causing a segmentation error. ...
- 144
2
votes
Accepted
pset2 Crack - Looping through fgets
Let's take a look at the man page of strcat():
char *strcat(char *dest, const char *src);
The strcat() function appends the src string to the dest
string, overwriting the terminating null ...
- 7,396
2
votes
Accepted
pset2 crack - conditional is not working
The var cracked is essentially a pointer, holding the address of the start of a string. if(cracked == argv[1]) is comparing a string's address to the address of argv[1], another string.
Next, strings ...
- 69.2k
2
votes
Accepted
Crypt is not doing what I think it should do
From the man page for crypt: (under Description)
The return value points to static data whose content is overwritten by
each call.
This means that each time you call crypt it encrypts the key ...
- 812
2
votes
Accepted
pset2 crack - stelios only password I can't crack
Other than the exact letters that are in it, it's no different from the others. I'll give you the hint that the first letter is 'A' Maybe your algorithm is somehow skipping that?
- 18.7k
2
votes
pset2 crack password does't work
You seem to have some misunderstanding about the crypt function. crypt takes 2 arguments, a string (like "abcd") and a salt (like "50").
You appear to be trying to compare individual chars.
The ...
- 18.7k
2
votes
Accepted
How to better condense individual for loops per amount of characters on crack.c
I did it in two ways.
First was recursive, depth-first search. Can also be implemented breadth-first.
I called my recursive function with a pointer to the memory to use, an index (initially 0) and ...
- 21k
2
votes
Accepted
PSet2 - Why does crack only work with four characters or less?
It doesn't work for 5 characters because you haven't allocated enough space for a 5-char string with char word[5]; Remember the null char!
As a consequence, when you set word = {'a', 'a', 'a', 'a', ...
- 18.7k
2
votes
Accepted
Pset2 can't crack stelios password
Did you let it run to completion or did you stop it while it was still running? This pset is notorious for running very long times for 5 letter passwords. Try running it overnight and see if it ...
- 69.2k
2
votes
Accepted
pset2/Crack - Terminal disconnected after some time of running
At pset3 recover/resize, they introduce the CS50 IDE at cs50.io, which I used. The lab has been unreliable for me, so I used that instead, pulling required files from https://github.com/cs50/labs/tree/...
- 21k
2
votes
Unable to get crypt to print correct hash
What's in alphabet?
password3[2] = alphabet[k];
The salt is the first two digits of the hash, not the first 3. password3[2] needs to be set to the end of string marker, '\0'.
If this answers your ...
- 69.2k
2
votes
Accepted
PSET6 CRACK (python)
Two things. First, and foremost, your program will keep going after it finds the password because your break only breaks out of the inner for loop. After finding the password, you should exit ...
- 18.7k
2
votes
Accepted
Week 2 CRACK: Erratic behavior with NULL '\0' when printing combinations of letters
This is a textbook example of "undefined behaviour". It gives different results on different machines because, well, there's a bug and there is no way to predict when or how it will "work" or fail.
...
- 28.6k
Only top scored, non community-wiki answers of a minimum length are eligible