cryptohack.org/challenges

enc1.py

# py2
import socket, json

conn = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
conn.connect(('socket.cryptohack.org', 13372))
conn.recv(100)  # "Gotta go fast!"

# OTP key len is 32 bytes (sha256 digest)
# by using all zeroes for input we don't need to de-XOR the key
input_data = '00' * 32
data = {'option': 'encrypt_data', 'input_data': input_data}
conn.send(json.dumps(data) + '\n')

resp = json.loads(conn.recv(1024))
print resp
key = resp['encrypted_data'].decode('hex')

# get encrypted flag
data = {'option': 'get_flag'}
conn.send(json.dumps(data) + '\n')

resp = json.loads(conn.recv(1024))
print resp
flag = resp['encrypted_flag'].decode('hex')

# decrypt flag
print ''.join(chr(ord(f) ^ ord(k)) for f, k in zip(flag, key))

conn.close()