Outputからフラグの文字数は37文字。shuffle128
711
Description
A weak version of RC4.
File
https://drive.google.com/file/d/1fRIQeOs8KeniRaH1vVANQUxCoBpAwxqv/view?usp=share_link
Author
@ndh
TetCTF{xxxxxxxxxxxxxxxxxxxxxxxxxxxxx}先頭7文字と最後の文字は確定、また不明な文字も上位1bitは0で確定している。randomにseed値が与えられているので、shuffledを再現できる。shuffledのうち確定しているbitとoutputより、keyを一部復元できる。またkeyは0～127で上位1bitが0であるため、outputとkeyよりshuffledを求めることができる。
if __name__ == '__main__':
from secret import FLAG
random.seed(2023)
print(sys.version)
prg = rc4_pseudo_random_generator(rc4_key_scheduling(FLAG))
for _ in range(64):
shuffled = shuffle(FLAG)
key = bytes(next(prg) for _ in range(len(FLAG)))
print(xor(shuffled, key).hex())
from bitarray import bitarray # https://pypi.org/project/bitarray/
import random
output = [
0x7dfdf6eba4da43bf7ca6eb64d3fbaac5e764b2c8e66e1f2a30e3b9e95b2ef48b28f105cdfc,
0x3353e19ed6a3ecad7716831b8cc149ad3a1990c8f4682c434d1b7f417e7df9e9ca0743fc3a,
0x2e15e68721c7773a920d9622cbad21b2d48e00358b1107b300ba19c3a48291dc1579eaf4f4,
0xe0f6b4e61390ce8d1eab002af797eb022c58a6576ef55c78b917268b9fe4d3f45dfc7d5dc3,
0xde11f01e825a69e5b1e004db1f79974ca9e42a2b0c0197dcb322f5a0e43cf7ddfdb529699d,
0x976dbf67bf2f67fd947c69696c5ef5bb9186b8031d279165a5fcd1f6ac9d7f668b847ecfc0,
0x01f123b89f75d3ab5f744caa4dd892eac598a0b1413cc0abf93509b2bc254a5714fd979f7a,
0x488b3d4d110f2dca864f6589a58033cc23ca3618db8ce59f398b7b9a6dfd93220e1cd02538,
0x6b92f7e54e6406b2d7d1176f5604e22cf4c6710ff35fa4cf7d33a7d1855a7f868da8713faa,
0xf9302dccf5c000ef69c2440fbe22b7eaeb5a95483dda09a0b0414e297ad81fb64fabc60025,
0xc9b5dcf6031051d3433ddc358f7e18b3f7cec58b37bace17f2fd1e39b1cac64fbfcdbff2aa,
0xbddac6c00310a5c80cb73d640a1b0592ed5d99984971a085941e7ea8e2fd0e86aaa1b7098f,
0x2ac7cdeb9e7eeb5abad2b4ed1238de39cb17aa4f4d8827ebd36d4a99acb9fb4e44cd365186,
0xb38ed3a76f5751faaca88fbae7ef53a6a4baa4f29b4bca0ef782b373969d3df62d9c276d69,
0x20f40b4267ae37f994dac8fccbb652d29abce709dc9f52223ddebe441899edfb8dc3a31a5d,
0xc9116855c08f1d04cbe6d86d0e9523c564fd3dd8bb79f7898ea7e624aba832e6530ad1231c,
0xb388f35a0f2009326bf66170156e57a36eea83285698fcdf2ba1fbbad199dc9d7860158d5e,
0x1f8c81249a0428cd781494ada971c49e1cd7121af374ecc70d902ad0f4f736e4ef23f61fc9,
0xb70d877d5ff8c38096faecb1de2df31ce467372c09c66c54b8e122123b539966937bb94d52,
0x72951dcfda3601c762b4ea5119e40e93bbe7a595a35db985cb990f3bbcc74ddc7157f0baff,
0xca0532f7df0239d0fe60e9a62852384f6cce737884808134fb1960e84803fb6ddc144df3c9,
0x78f35e7e26df365e213787a3885ca11c76d14fb998d4a440826b2d8adaa5fe85065c9e9c0d,
0xf3110f509bd39e5ead882e85ccb31906809a0c29e33a79f0b3229e671dba1353c89968c4a4,
0x2ac15e7a5dcc821c58ac08d526e5a350ef994bb485fc1c916f59e366e6f7e7ddc76b4a0cae,
0x381a2afbc6aa95643248d8dd39c44fd7090746af9fa3f3c4f70ba56298d6ca1b36b7d19ec8,
0xb098dfffe1cd19019ba9c472f6f966964352a958eda8707553021870ba51c9a0b573a59f99,
0x02578a8b58c1e9c9d5f4321e0b8eb66922905ec2dfd3bf1a6ef583fcce8846243cf6c609d9,
0x93efb1acf6b268c5a79746a28c64adbbbc81924991e13aa971d64f4087c87650ebb6309daa,
0x9fcbff37a9919d676e6ce86d9bae8f75376b1a7a76de304c622fe163ea7549a8dcccb095f7,
0xad25c09cdcc768b53a519daf6f1a0861b4c9530cc9d0cf82fbf7c9f5a9acc2346d611a21d0,
0x08aee3c019e664d88f3f1147c4f52d33f2f4ab9fea176625f24a14d517a1d59d338e5bf0aa,
0x479de7e5e8e7841382bb7c9c844f7f8d900979bd360c6d84dc69bd17e7f4ced202afce5964,
0x65c43c740e68be4ac64c559f09b461904be78fe5f5eaa6f78afb23a1d9c12ecf1d14a287a3,
0x90063ef6a3b48091f514f1b87dc3ef40942989648043df1dda7d1221c0efea863f69f2fba6,
0xe4c2976ec29fec9cc3d04ec5f4dde4e282886be0c5ee471ccb8cd201558adb759375c27d78,
0x1ec9458af0857b6f437ee5d72de707eb6d38df96a830bb53775667f9722a46869e0954b5ad,
0x5de6f6df232cc29f3fcaac177f323ecfd99732e7559f9d6ffdd706e387bcc23127891be4e1,
0x7df2884288490b19fd7d20c746508c3ee8e77706c549ba5a07bf9cc183ede90e5cdd6cc59b,
0x6ebc5d2caff2d0fc8afb538ea990f4289f716375834a67966dc6eba35b7559726826c23bd4,
0xe6bdfbfe7f094d6ecfdf76433cfc3c64c5041ad8aeaf84ba5c8473b24d836f332e8e41eabe,
0x6b845fefb8e5fe2253600c137047ee029a1bab28e9b45eda71597169148593938049092ee2,
0x1172b4a57311da2ff968e1071c4eff0bd22a333cfdc8a6fdef41a4b98f69620152bbeb60b5,
0x5a788ee6a476eaaa3f581eaebc2589efa640ac37fc5faa4f3591b7db58234dd8fb9743192d,
0x07d49bf8af3cf3ac77db932a41b81d61736b7e8f5bb656b2a9637f57b7871c1297bf5e3b14,
0x94d1d09e9c3d024538c4e5fedafbf5aed564d9998dec700647f704115f281efe74aefc0231,
0xb11b4ff19b77cd69f1881e5401c6e56a9bbf2e88bb443b3340de8d01c4768c6efa34233b35,
0xdfc7edc0fa6232d7df18717c9dec7631295a035afdeeea7e2dfaec3518e58c8189f65dd52f,
0x5490e892fca7f4be4312ad69b1eed46e11cb94bf8bafd2ef725e77fd9620ba980fa1d46563,
0xb9066eb49cb42ecfdcd9f7713e0feddb920043908df127cf35386df3b4bce6fab3c6a3e89f,
0x8c51507ea79ffb2914436f8c9fa39501d89b8f9446cbe2fcfb0bada4886ff76b20ce1e29f3,
0x6df94fc313b82da575073aeb54c35e5d3ff0c9dc7032cbffcc92b47b2fead75610d6157bca,
0xb92cf23e538fc6b3d1c0e28dd81f3c2a58d890bf323da321a39c9fb601caee4bcc1ccc9abd,
0x0cc0985f966eb484c5f26b9bb8821dabf3b88d3471b55c6351a43fde32428519241a0ddd76,
0x78cf7e7bf1ffa53812d1c9b47fc23852b2fcd318f7ea21dba12ad3a1d4f38e2ba1a5116aa9,
0xe35e377f7972b49fbb82a42f90443ca77adb678fa278bf93046c8ec2bc05cb2155d5b506d6,
0x3bc4ffa6eb16c6da6c40d78b132131092bc8f0696a81e14deca5018daea56c6678befbc1f8,
0x138d167661180fc7b7c52fa821c518a29d41c5a73aee9969f74b096cff8fca7ead4f5affe9,
0x3784f8b584545b1ef09aa3815182776966eb9d4758f25ae89550aee3916dce6f40d29c79ee,
0x09913e8ed1778c95cbac302c86cc4ba5ad8b5fe113c78352d00979e84dcd10c3ecd036fba0,
0xd1ed85304ea4a3e03233544efb85017c9cd1d3259d959acc0f0dbdaece9ed668d937d52309,
0xe6b89393cfd0e888c8dce582495d216760eb1a8032103351d15c8033a46aae338a11ac99ee,
0x92683cb1cb9f24a7925395f54be8b0e520ffd5afbc80c11256e33324bf2509a1c9b64f46dc,
0x0b7e5204fba4ceec74ee7b35417ecb88fa8a74c6575bb6de8f15f1257b6e02a42e4b56dff0,
0x49d609e06cb04aa787ebe99d741d4b60b909a00c0de6faecbf4c6d21559495a7c67060625d,
]
from Crypto.Util.number import bytes_to_long, long_to_bytes
if __name__ == '__main__':
#from secret import FLAG
FLAG = b"TetCTF{89012345678901234567890123456}"
bit = [False for _ in range(len(FLAG)*8)]
for i in range(len("TetCTF{")*8):
bit[i] = True
for i in range(8):
bit[len(FLAG)*8-i-1] = True
for i in range(0, len(FLAG)*8, 8):
bit[i] = True
flag_bit = bitarray()
flag_bit.frombytes(FLAG)
test = [i for i in range(len(FLAG)*8)]
shuffleds = []
random.seed(2023)
for _ in range(64):
test2 = test[:]
random.shuffle(test2)
shuffleds.append(test2)
print(shuffleds)
for _ in range(2):
keys = []
for i in range(64):
shuffled = shuffleds[i]
out = bitarray()
out.frombytes(long_to_bytes(output[i]))
key = []
for j in range(len(FLAG)*8):
s = shuffled[j]
if bit[s]:
k = flag_bit[s] ^ out[j]
if j%8==0:
assert(k==0)
key.append(k)
else:
if j%8==0:
k = 0
f = out[j] ^ k
key.append(k)
flag_bit[s] = f
bit[s] = True
else:
key.append(None)
keys.append(key)
print(keys)
print(bit)
print(bytes(flag_bit))
TetCTF{____1nsuff1c13nt_3ntr0py_____}
Paul, Goutam
Routledge
2019-09-19
