```
# Solve the task using SageMath.
# command used to extract matrix and vector data :)
# tshark -r a.pcap -Y "data.len>0" -T fields -e tcp.stream -e data

p = 340282366920938463463374607431768211297
f = open('dump.txt')
import re
A = []
b = []
lines = f.readlines()
for i in range(len(lines)):
if i % 3 == 2:
items = re.split('\\s+', lines[i].strip())
ciphertext = items[1].decode('hex').split('\n')[1].strip().decode('hex')
elif i % 3 == 0:
nums = re.split('\\s+', lines[i].strip())
nums = nums[1].strip().decode('hex')
nums = nums.split()
nums = map(int, nums)
A.extend(nums)
else:
nums = re.split('\\s+', lines[i].strip())
nums = nums[1].strip().decode('hex')
b.append(int(nums))

A = matrix(GF(p), 40, A)
b = vector(GF(p), b)
key = A.solve_right(b)

from hashlib import sha256
from Crypto.Cipher import AES

aeskey = sha256(' '.join(map(str, key)).encode('utf-8')).digest()
cipher = AES.new(aeskey, AES.MODE_CFB, '\x00'*16)

print [cipher.decrypt(ciphertext)]
```