Easy Peasy

KEY_FILE = "key"
KEY_LEN = 50000
FLAG_FILE = "flag"

def startup(key_location):
	flag = open(FLAG_FILE).read()
	kf = open(KEY_FILE, "rb").read()

	start = key_location
	stop = key_location + len(flag)

	key = kf[start:stop]
	key_location = stop

	result = list(map(lambda p, k: "{:02x}".format(ord(p) ^ k), flag, key))
	print("This is the encrypted flag!\n{}\n".format("".join(result)))

	return key_location

result = list(map(lambda p, k: "{:02x}".format(ord(p) ^ k), flag, key))

def encrypt(key_location):
	ui = input("What data would you like to encrypt? ").rstrip()
	if len(ui) == 0 or len(ui) > KEY_LEN:
		return -1

	start = key_location
	stop = key_location + len(ui)

	kf = open(KEY_FILE, "rb").read()

	if stop >= KEY_LEN:
		stop = stop % KEY_LEN
		key = kf[start:] + kf[:stop]
	else:
	key = kf[start:stop]
	key_location = stop

	result = list(map(lambda p, k: "{:02x}".format(ord(p) ^ k), ui, key))

	print("Here ya go!\n{}\n".format("".join(result)))

	return key_location

if stop >= KEY_LEN:
	stop = stop % KEY_LEN
	key = kf[start:] + kf[:stop]
else:
	key = kf[start:stop]

from pwn import *

KEY_LEN = 50000

p = remote("mercury.picoctf.net", 11188)

p.recvuntil(b"flag!\n")
enc_flag = p.recvline().strip()
enc_flag_len = len(enc_flag) // 2       # 32

to_enc = b"A" * (KEY_LEN-enc_flag_len)
p.sendlineafter(b"encrypt? ", to_enc)

# now enc flag...
p.sendlineafter(b"encrypt? ", bytes.fromhex(enc_flag.decode()))
p.recvline()
flag = p.recvline().strip()

print(b"picoCTF{" + bytes.fromhex(flag.decode()) + b"}")

from pwn import *

KEY_LEN = 50000

p = remote("mercury.picoctf.net", 11188)

p.recvuntil(b"flag!\n")
enc_flag = p.recvline().strip()
enc_flag_len = len(enc_flag) // 2       # 32

to_enc = b"A" * (KEY_LEN-enc_flag_len)
p.sendlineafter(b"encrypt? ", to_enc)

# now enc flag...
p.sendlineafter(b"encrypt? ", bytes.fromhex(enc_flag.decode()))
p.recvline()
flag = p.recvline().strip()

print(b"picoCTF{" + bytes.fromhex(flag.decode()) + b"}")

# picoCTF{7904ff830f1c5bba8f763707247ba3e1}