#!/usr/bin/env python3
from hashlib import sha1

with open('binaryfile', 'rb') as bin:
    binary = bin.read()

base = 0x1234
for seq in [[0xec, 0xb0, 0xaa, 0xaf], [0xed, 0xb0, 0xaa, 0xaf], ...]:
    copy = binary[0:base]
    copy += bytes(seq)
    copy += binary[base+len(seq):]
    if sha1(copy).hexdigest() = '9968733ce3ff0893bbb0a19e75faaf2fb0000e19':
        print('success with bytes {0}'.format(seq))
        break
else:
    print('no success')