[HGAME 2023 week2]stream lingfeng的WriteUp


# import dis,marshal
# a=open('stream.pyc','rb')
# a.seek(16)
# dis.dis(marshal.load(a))
import base64

def gen(key):
    s=list(range(256))
    j=0
    for i in range(256):
        j = (j + s[i] + ord(key[i % len(key)]) % 256) % 256
        tmp = s[i]
        s[i] = s[j]
        s[j] = tmp

    i = 0
    j = 0
    data = []

    for _ in range(50):
        i = (i + 1) % 256
        j = (j + s[i]) % 256
        tmp = s[i]
        s[i] = s[j]
        s[j] = tmp
        data.append(s[(s[i] + s[j]) % 256])

    return data
def encrypt(text,key):
    result = ''

    for c, k in zip(text, gen(key)):
        result += chr(ord(c) ^ k)

    result = base64.b64encode(result.encode()).decode()

    return result
def decrypt(result,key):#我自己加上的
    result = base64.b64decode(result.encode()).decode()
    text=''
    for c, k in zip(result, gen(key)):
        text += chr(ord(c) ^ k)


    return text
text = input("Flag:")
key = 'As_we_do_as_you_know'
enc = encrypt(text, key)
if enc=='wr3ClVcSw7nCmMOcHcKgacOtMkvDjxZ6asKWw4nChMK8IsK7KMOOasOrdgbDlx3DqcKqwr0hw701Ly57w63CtcOl':
    print('yes')
else:print('try again...')


print(decrypt('wr3ClVcSw7nCmMOcHcKgacOtMkvDjxZ6asKWw4nChMK8IsK7KMOOasOrdgbDlx3DqcKqwr0hw701Ly57w63CtcOl',key))