Add an old tool I found on my HDD to decrypt obfuscated EXEs from Twinkle games

master
987123879113 3 months ago
parent d456263f4b
commit 35d6f95748
  1. 47
      twinkle/twinkle_iidx_mgp_genkey.py

@ -0,0 +1,47 @@
import argparse
def generate_key(filename):
key = 0
for c in filename[-6:][::-1]: # Not necessary to reverse the string, but the real game reads from the tail backward so recreate for accuracy
key += ord(c)
if ord(c) - 0x61 >= 0x1a:
# I'm not sure of anything that hits this path so I can't verify, but it's in the ASM code
key += 0xffe0
return key & 0xffff
def decrypt_data(input_key, input_filename, output_filename):
key = generate_key(input_key)
print("Key: %s -> %04x" % (input_key, key))
print("Decrypting %s..." % input_filename)
with open(input_filename, "rb") as infile:
data = bytearray(infile.read())
for i in range(0, len(data), 2):
curdata = ((data[i+1] << 8) | data[i]) ^ key
data[i] = (((curdata & 0x1c00) >> 5) | (curdata & 0x1f)) & 0xff
data[i+1] = (((curdata & 0xe000) >> 8) | ((curdata & 0x3e0) >> 5)) & 0xff
key = (key + 0x71) & 0xffff
with open(output_filename, "wb") as outfile:
outfile.write(data)
print("Saved to %s!" % output_filename)
if __name__ == '__main__':
parser = argparse.ArgumentParser()
parser.add_argument('--input', help='Input file', required=True)
parser.add_argument('--output', help='Output file', required=True)
parser.add_argument('--key', help='String to be used for key (usually the file path from root, such as "/DATA/511.MGP")', required=True)
args = parser.parse_args()
decrypt_data(args.key, args.input, args.output)
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