注意：这道题需要脱壳，而且需要改特征值，详细请看
LitCTF 2024hello_upx------入土为安的第一天-CSDN博客
脱完壳发现有256这个特殊的数，是rc4类型的题，最后有一个异或
a = "9F041CEFA92386B6F56F27B96155FD42"
aa = "5E4C614B08306D1502BC6854D68716D4"
Splitting strings into pairs of hexadecimal characters
b = a\[i:i+2 for i in range(0,len(a),2)]
c = b::-1
d1 = ''.join(c)
b = aa\[i:i+2 for i in range(0,len(aa),2)]
c = b::-1
d2 = ''.join(c)
print(d1)
print(d2)
Concatenating d1 and d2
encode = d1 + d2
print(encode)
Converting concatenated string to list of integers
ddd = int(encode\[i:i+2,16) for i in range(0,len(encode),2)]
Initialize flag list
flag = \[\]
Initializing variables
v22 = 0*256
v20 = 0*256
key = ord(i) for i in "justfortest"
print(key)
Initialization of S-box v22 and v20
for i in range(256):
v22i = i
v20i = keyi % len(key)
v5 = 0
for i in range(256):
v8 = v22i
v5 = (v8 + v20i + v5) % 256
v22i, v22v5 = v22v5, v22i
v9 = 0
v10 = 0
Encryption process
for i in range(len(ddd)):
v10 = (v10 + 1) % 256
v11 = v22v10
v9 = (v11 + v9) % 256
v22v10, v22v9 = v22v9, v22v10 # Swap
flag.append(dddi ^ v22(v22\[v10 + v22v9) % 256])
Printing encrypted flag in hexadecimal
hex_flag = hex(f) for f in flag
print(hex_flag)
Attempting to decode encrypted flag to string (handle UnicodeDecodeError)
try:
decrypted_text = ''.join(chr(f) for f in flag)
print("Decrypted text:", decrypted_text)
except UnicodeDecodeError:
print("Decryption result contains non-printable characters.")
Printing encrypted flag as ASCII characters (for demonstration, may cause errors)
for i in range(len(flag)):
try:
print(chr(flagi), end='')
except ValueError:
print("Non-printable", end='')
