Rating: 4.0
We have the following code
```python
# ENCRYPT.py
from sympy import isprime, prime
flag = '<REDACTED>'
def Ord(flag):
x0r([ord(i) for i in flag])
def x0r(listt):
ff = []
for i in listt:
if isprime(i) == True:
ff.append(prime(i) ^ 0x1337)
else:
ff.append(i ^ 0x1337)
b1n(ff)
def b1n(listt):
ff = []
for i in listt:
ff.append(int(bin(i)[2:]))
print(ff)
if __name__ == "__main__":
Ord(flag)
'''
OUTPUT :
[1001100000110, 1001100000100, 1001100000100, 1001100000000, 1001101100010, 1001101100111, 1001101001100, 1001101001111, 1001100000111, 1001101000101, 1001101101000, 1001100000011, 1001101011001, 1001101110011, 1001101101000, 1001101110101, 1001101011110, 1001101011001, 1001100000011, 1001011001010, 1001101100101, 1001101001110, 1001101101000, 1001101110010, 1001101011001, 1001001111100, 1001100000111, 1001101010011, 1001100000100, 1001101000101, 1001101101000, 1001100000011, 1001101000101, 1001100000100, 1001101101000, 1001101000011, 1001101111111, 1001100000100, 1001101101000, 1001101100000, 1001100000100, 1001100000011, 1000101111100, 1001100000100, 1001111000110, 1001101000011, 1001101101000, 1001100001111, 1001100000111, 1001100000000, 1001100001110, 1001100000111, 1001100000000, 1001111000110, 1001100000001, 1001101001010]
'''
```
We can easily decode the output by reversing the process.
```python
from sympy import isprime, prime, sieve
# Transforms base2 to base10.
def unb1n(bin):
dec = []
for i in bin:
b = str(i)
#print(b, int(b,2))
dec.append(int(b,2))
return unx0r(dec)
def unx0r(lista):
un = []
for i in lista:
x = i ^ 0x1337
if isprime(x):
# if the number we get is prime it means we need
#to get its index in the sieve to get the original number
un.append(sieve.search(x)[0])
else:
un.append(x)
return to_char(un)
def to_char(lista):
return "".join(chr(c) for c in lista)
bin = [1001100000110, 1001100000100, 1001100000100, 1001100000000, 1001101100010, 1001101100111, 1001101001100, 1001101001111, 1001100000111, 1001101000101, 1001101101000, 1001100000011, 1001101011001, 1001101110011, 1001101101000, 1001101110101, 1001101011110, 1001101011001, 1001100000011, 1001011001010, 1001101100101, 1001101001110, 1001101101000, 1001101110010, 1001101011001, 1001001111100, 1001100000111, 1001101010011, 1001100000100, 1001101000101, 1001101101000, 1001100000011, 1001101000101, 1001100000100, 1001101101000, 1001101000011, 1001101111111, 1001100000100, 1001101101000, 1001101100000, 1001100000100, 1001100000011, 1000101111100, 1001100000100, 1001111000110, 1001101000011, 1001101101000, 1001100001111, 1001100000111, 1001100000000, 1001100001110, 1001100000111, 1001100000000, 1001111000110, 1001100000001, 1001101001010]
print(unb1n(bin))
```
```shell
❯ python solve.py
1337UP{x0r_4nD_Bin4aRy_EnC0d3r_4r3_tH3_W34k35t_80790756}
```
