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Matasano Crypto Challenges

Name: Anonymous 2013-09-11 2:23

Anyone done these before? Looks like fun, just sent the request e-mail. I'll try to report back!

We've built a collection of 48 exercises that demonstrate attacks on real-world crypto.

This is a different way to learn about crypto than taking a class or reading a book. We give you problems to solve. They're derived from weaknesses in real-world systems and modern cryptographic constructions. We give you enough info to learn about the underlying crypto concepts yourself. When you're finished, you'll not only have learned a good deal about how cryptosystems are built, but you'll also understand how they're attacked.
http://www.matasano.com/articles/crypto-challenges/

Name: ‮‭ 2013-09-15 19:10

>>21
First, do bi-direction correctly in the name filed.

Second, file(), od(), or check if bytes are 256 byte works or more. Simple as that.

Name: Anonymous 2013-09-15 22:27

>>24
http://linux.die.net/man/1/file
http://linux.die.net/man/1/od

Also recall strings are usually 7 bits or 8. This is a size length technique.

Name: Anonymous 2013-09-16 15:31

>>21

$ cat is_plaintext.c
#include <stdio.h> /*
set -e
gcc -O3 -o is_plaintext is_plaintext.c
exit 0
*/
#define BUFFA_SIZE 100
int main() {
  unsigned int good=0,bad=0;
  int i;
  unsigned char buffa[BUFFA_SIZE];
  size_t bytes_read = fread(buffa,1,BUFFA_SIZE,stdin);
  for (i=0;i<bytes_read;i++) {
    unsigned char c = buffa[i];
    if ((c >= 32 && c <= 127) || c == 10)
      good++; else bad++;
  }
  return (bad*2 < good) ? 0 : 1;
}

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Matasano Crypto Challenges

1 Name: Anonymous 2013-09-11 2:23

22 Name: ‮‭ 2013-09-15 19:10

26 Name: Anonymous 2013-09-15 22:27

28 Name: Anonymous 2013-09-16 15:31

Name: Anonymous 2013-09-11 2:23

Name: ‮‭ 2013-09-15 19:10

Name: Anonymous 2013-09-15 22:27

Name: Anonymous 2013-09-16 15:31