Tags: compare ascii
Rating:
# Sherlock (crypto)
```
Sherlock has a mystery in front of him. Help him to find the flag.
```
###ENG
[PL](#pl-version)
In the task we get a [book](sherlock.txt).
We figured we could compare it to the [original text from Project Gutenberg](sherlock_orig.txt).
We had to make it lowercase and remove the ToC but other than that the comparison was simple:
```python
import codecs
def main():
with codecs.open("sherlock.txt", "r") as input_file:
task_data = input_file.read()
task_data.replace("\n\n", "\n")
with codecs.open("sherlock.txt", "r") as input_file:
original_data = input_file.read()
original_data = original_data.lower()
original_data.replace("\n\n", "\n")
result = "".join([task_data[i] for i in range(len(task_data)) if task_data[i] != original_data[i]])
print(result)
main()
```
This gave us a long string with `ZEROONEZERO...`.
We changed this into a number and interpreted as text:
```python
from crypto_commons.generic import long_to_bytes
result = result.replace("ZERO", "0")
result = result.replace("ONE", "1")
print(long_to_bytes(int(result, 2)))
```
And we got `BITSCTF{h1d3_1n_pl41n_5173}`
###PL version
W zadaniu dostajemy [książkę](sherlock.txt).
Postanowiliśmy porównać ją z [oryginalnym tekstem z Project Gutenberg](sherlock_orig.txt).
Musieliśmy zmienić ją na lowercase i usunąć spis treści, ale cała reszta była prosta:
```python
import codecs
def main():
with codecs.open("sherlock.txt", "r") as input_file:
task_data = input_file.read()
task_data.replace("\n\n", "\n")
with codecs.open("sherlock.txt", "r") as input_file:
original_data = input_file.read()
original_data = original_data.lower()
original_data.replace("\n\n", "\n")
result = "".join([task_data[i] for i in range(len(task_data)) if task_data[i] != original_data[i]])
print(result)
main()
```
To dało nam długi string `ZEROONEZERO...`.
Po zmianie tego na liczbę a następnie zinterpretowaniu jako tekst:
```python
from crypto_commons.generic import long_to_bytes
result = result.replace("ZERO", "0")
result = result.replace("ONE", "1")
print(long_to_bytes(int(result, 2)))
```
Dostaliśmy `BITSCTF{h1d3_1n_pl41n_5173}`
