GryphonCTF_2016: Anomaly

Category: Programming Points: 25 Description:

I have made this file by using SHA-512 512 times on every number from 1 to 1000000. The first round uses the string format of the number while subsequent rounds uses the hex digest of previous rounds. However there are some anomalies in the file when Qiurong ran the same program. Can you find out the anomaly for me? Alternative (faster) download link WARNING: 123MB file Creator - Kelvin Neo (@deathline75)

Write-up

A WONDERFUL CHALLENGE BY @DEATHLINE75 /s.

We have a file, about 1000000 lines long and it's big and thus I won't be giving a download link. First up, we generate our own file to check back with the given file.

import hashlib

hashes = []
for i in range(1000000):
    hash = str(i)
    for iters in range(512):
        hash = hashlib.sha512(hash).hexdigest()

with open('hashes.txt', 'w') as file:
    for line in hashes:
        file.write(line + '\n')

Comparing the two files, we get,

===
51078
======
79e14f7e16192678e4f202aaac5d0ec8d90f28a4ebe467588f175abdc601678d6544f977c81eba9d1c4a95c34fda85752b19098b827f2bbc876db1553617ca96 !=  79e14f7e16192678e4f202aaac5d0ec8d90f28a4ebe467588f175abdc601678d6544f977c81eba9d1c4a95c34fda85752b19098b827f2bbc876db1553617ca4f
===
53477
======
cd86dd387a943bb25b2fd81ba88ec1f9cdbcbfc3ab3d9ecd1c762a55920bb3f3a3a783b86c20708d8cbc357968dc7f2680f3d9f6de140a86de22806d5848c7f4 != cd86dd387a943bb25b2fd81ba88ec1f9cdbcbfc3ab3d9ecd1c762a55920bb3f3a3a783b86c20708d8cbc357968dc7f2680f3d9f6de140a86de22806d5848c837
===
165716
======
82e98cd1d1f9a0e33b8a0442f6f33a32e15f18a716f81307c1dee6bc854f42dc0e83cfdd83be2ebcc5bca8b97d02762d04160948e030e259b545c0e11a66711a != 82e98cd1d1f9a0e33b8a0442f6f33a32e15f18a716f81307c1dee6bc854f42dc0e83cfdd83be2ebcc5bca8b97d02762d04160948e030e259b545c0e11a6670c6
===
244162
======
86f5a78aa20de48dabadb5868386e01fdd793292217e77fd8f8de2e3863b9d3f811fe8b6c5d85446355f187d3ef7774595a382ce163699826c0d2e8008ca9251 != 86f5a78aa20de48dabadb5868386e01fdd793292217e77fd8f8de2e3863b9d3f811fe8b6c5d85446355f187d3ef7774595a382ce163699826c0d2e8008ca920b
===
256030
======
7dab38088e97401ab1ee3d6389c49047eb23b10895f78299487d3fedbc54ca3cb127910c111c06082addb396f5957c0c9038d725a76999048a2d62620eb8ee4e != 7dab38088e97401ab1ee3d6389c49047eb23b10895f78299487d3fedbc54ca3cb127910c111c06082addb396f5957c0c9038d725a76999048a2d62620eb8edd3
===
259971
======
2d3d1644ac279cfe75a36cfb2ea53c16622fbec3716884df120f1bc9aafd47c48e3f9aee16e32512057bf656cf40d5a6392b9efa82a6fc21beb859c09a853a9a != 2d3d1644ac279cfe75a36cfb2ea53c16622fbec3716884df120f1bc9aafd47c48e3f9aee16e32512057bf656cf40d5a6392b9efa82a6fc21beb859c09a853acf
===
339025
======
dcd2acaa313c861acb7c4d3128df2b8035c3a3124d9f9554cb95d88686fa20dffa6379e7e04dcece28d0c21f0907af8cc4792f6b259d9cf5a6ab74792b8d9c7d != dcd2acaa313c861acb7c4d3128df2b8035c3a3124d9f9554cb95d88686fa20dffa6379e7e04dcece28d0c21f0907af8cc4792f6b259d9cf5a6ab74792b8d9ce5
===
423605
======
b15d73389d194feea6eb4a27e52f52cd7b86033746d0f0c27c2c8a50a593b94c101a49073e4fc6313f52298719ce2236f40739140d713eafb20eddfb42ba3dae != b15d73389d194feea6eb4a27e52f52cd7b86033746d0f0c27c2c8a50a593b94c101a49073e4fc6313f52298719ce2236f40739140d713eafb20eddfb42ba3de2
===
434116
======
79c827550005100f4604d48c4057cad429c47785f8725f444915a6fdf7b7ae15232ceee4ed08fc64714c7c3a9bf2409f3ed095d4f479e1458f16f00175f2379a != 79c827550005100f4604d48c4057cad429c47785f8725f444915a6fdf7b7ae15232ceee4ed08fc64714c7c3a9bf2409f3ed095d4f479e1458f16f00175f2376d
===
442288
======
8fa90152c8419a4b8953e9140731f0218b53968d5475926a0ff319e6a0c2dd65a6ea57713a765434d87fbec32d8373856fa85fb716dd02f6262f6ad8e64277ce != 8fa90152c8419a4b8953e9140731f0218b53968d5475926a0ff319e6a0c2dd65a6ea57713a765434d87fbec32d8373856fa85fb716dd02f6262f6ad8e642775c
===
480014
======
698c4f43443a84d575c45417afc8c6834d42c61405e5f3d13e99f387519b807630401677284cc90b4b89779f244adbc5c7d7d5670db7f14166c8b8ddc1bfe521 != 698c4f43443a84d575c45417afc8c6834d42c61405e5f3d13e99f387519b807630401677284cc90b4b89779f244adbc5c7d7d5670db7f14166c8b8ddc1bfe4af
===
518215
======
ea583b10dc85bbdd1b4a3d8c26da477edd974420dc6118585eab9f644ca6d259ce3f425fef486c884c6574b7b2478743e8aa092e1beebad8eb9e3e39453bbd19 != ea583b10dc85bbdd1b4a3d8c26da477edd974420dc6118585eab9f644ca6d259ce3f425fef486c884c6574b7b2478743e8aa092e1beebad8eb9e3e39453bbd92
===
523064
======
44416ef05be7876d3ae98a0d9d5e383a6e7b89a83cfb20f2ea976dd78f3309a6b53123b4b3013bc2157ca9ab4f593bd2cd65278c18aae3b588ede6296a3cfedc != 44416ef05be7876d3ae98a0d9d5e383a6e7b89a83cfb20f2ea976dd78f3309a6b53123b4b3013bc2157ca9ab4f593bd2cd65278c18aae3b588ede6296a3cfe7d
===
525137
======
356adb1a8aacfff6cc63eda8553d4714581501318f2e3400bbe3e07756e4ddf4083ace119e8fe12a7d4020d63a9ea17bb6d8394557b85c0c0b9b049b21f85cb8 != 356adb1a8aacfff6cc63eda8553d4714581501318f2e3400bbe3e07756e4ddf4083ace119e8fe12a7d4020d63a9ea17bb6d8394557b85c0c0b9b049b21f85ced
===
538035
======
0b625bfbaf9aabb35dc885f379cdc0e2e4d1aa80d33380789fa7097a75c7ae56aacd7cc6c770a1c674da33c1b02ddd644e4601297079c91301ae7fbc9bcb0f33 != 0b625bfbaf9aabb35dc885f379cdc0e2e4d1aa80d
 33380789fa7097a75c7ae56aacd7cc6c770a1c674da33c1b02ddd644e4601297079c91301ae7fbc9bcb0f9b
===
613916
======
dd92300d2b36b86cfbb6c7b3742063f487fa04fe8f49e4a329a3ae293bc912e8032b07d94668e845bc96e5c3d74cb6ee8dda629882add6191f231fb776e6e3d8 != dd92300d2b36b86cfbb6c7b3742063f487fa04fe8f49e4a329a3ae293bc912e8032b07d94668e845bc96e5c3d74cb6ee8dda629882add6191f231fb776e6e3a4
===
616679
======
875beba523c9361a38f1474cca161a11f8b429640c0e8bf330ea50f7894f1263bd6ddf9901689d71a6685f6ae3457379220e88026b2a39c4ea37dd6cd05c9ebe != 875beba523c9361a38f1474cca161a11f8b429640c0e8bf330ea50f7894f1263bd6ddf9901689d71a6685f6ae3457379220e88026b2a39c4ea37dd6cd05c9eeb
===
626301
======
9a109cec88210524e7e647505ecc1cf385c5632275b8591f189a5358bb570aaf5ad3e5906e2bdd39fc4214b58391c479d078101128237193831825c237739c92 != 9a109cec88210524e7e647505ecc1cf385c5632275b8591f189a5358bb570aaf5ad3e5906e2bdd39fc4214b58391c479d078101128237193831825c237739d04
===
641793
======
5d7775af25bf7c6ee7c5145de74fa35778fd228a8ad2ab39279db92244bcef7e1fe520aa4d165eb3dbd7bf535b219dd104fda8ad8473cba7a500fcfff9be8ac8 != 5d7775af25bf7c6ee7c5145de74fa35778fd228a8ad2ab39279db92244bcef7e1fe520aa4d165eb3dbd7bf535b219dd104fda8ad8473cba7a500fcfff9be8b3a
===
660095
======
fdba2c65e9dfebe2b1c1afc714ed9a3c33f4a872d9ffa09f67e07f02c11422ea5d381175c851a969e85f9b2451e80502e12d043abdc99f79be0cdbad31e0445b != fdba2c65e9dfebe2b1c1afc714ed9a3c33f4a872d9ffa09f67e07f02c11422ea5d381175c851a969e85f9b2451e80502e12d043abdc99f79be0cdbad31e044d4
===
704921
======
bef8c892187ae2c4c1bd6db6ea3102d57f21c053c2d92119e482459e71cf003d4a4186986671136aa66bd2f95fc1936df1980b884850a1340ce6bd5cfdb9879c != bef8c892187ae2c4c1bd6db6ea3102d57f21c053c2d92119e482459e71cf003d4a4186986671136aa66bd2f95fc1936df1980b884850a1340ce6bd5cfdb987fb
===
773589
======
c10b537a5d07331ba46ea8e6368c191c17160a6984bfee8db7d27f2f1db2bbed19f2dc03c72930e3b7b815196c5b53ee8fb728fb9f37ab8d6f5da6f630df228e != c10b537a5d07331ba46ea8e6368c191c17160a6984bfee8db7d27f2f1db2bbed19f2dc03c72930e3b7b815196c5b53ee8fb728fb9f37ab8d6f5da6f630df22fc
===
786375
======
b0e8232e6faee3b7827020ef0d07cf9068872035332d57d9bcba0ba505024c107dbceb0356217fb0f0026d4176a8b0a990ea8439269804f207babb108d2d90da != b0e8232e6faee3b7827020ef0d07cf9068872035332d57d9bcba0ba505024c107dbceb0356217fb0f0026d4176a8b0a990ea8439269804f207babb108d2d910b
===
812113
======
856b15b031a2c3b1221f35fd46f0263bdd32d884d3608712d98cae60d3771a9eda5d5dbf68ceb6428fa82c755b5dd0fcdc60803ca6e67997ca258daaad25df1b != 856b15b031a2c3b1221f35fd46f0263bdd32d884d3608712d98cae60d3771a9eda5d5dbf68ceb6428fa82c755b5dd0fcdc60803ca6e67997ca258daaad25df51
===
819872
======
731d52c08f8761e11ad2dd849df7ec25522b82af38d8facc9d8aac12275d20e419b5b427eece9c1776840d57ce2a6d8266a35bdb28407af4e4ad33d91170e6f6 != 731d52c08f8761e11ad2dd849df7ec25522b82af38d8facc9d8aac12275d20e419b5b427eece9c1776840d57ce2a6d8266a35bdb28407af4e4ad33d91170e68e
===
833648
======
48ed7448cfd5cfa027481694e0181015844f3901b68260ddad96814eb5a8bc4d2de65b938ed34ca2ca61e95ec43abdb925ca87351beed522eccf7228e01ed6fe != 48ed7448cfd5cfa027481694e0181015844f3901b68260ddad96814eb5a8bc4d2de65b938ed34ca2ca61e95ec43abdb925ca87351beed522eccf7228e01ed6c7
===
883221
======
fd69c00d3cd773062118dbfa0e2cb1d4157e10e11aba801bdbc38ef335bf11336a4efa9f87d05c305777a58f0019f99ac76cf2a6217465974518900e575cc678 != fd69c00d3cd773062118dbfa0e2cb1d4157e10e11aba801bdbc38ef335bf11336a4efa9f87d05c305777a58f0019f99ac76cf2a6217465974518900e575cc6f5

Hmm... what now? Removing similar characters, we get

96 != 4f
7f4 != 837
11a != 0c6
51 != 0b
e4e != dd3
9a != cf
c7d != ce5
ae != e2
9a != 6d
ce != 5c
521 != 4af
19 != 92
dc != 7d
b8 != ed
33 != 9b
d8 != a4
be != eb
c92 != d04
ac8 != b3a
5b != d4
9c != fb
8e != fc
0da != 10b
1b != 51
f6 != 8e
fe != c7
78 != f5

Hmm... Converting GCTF into hexadecimal, we get 47 43 54 46. Let's try a few things.

967f411a51e4e9ac7dae9ace52119dcb833d8bec92ac85b9c8e0da1bf6fe78 [all length]
96f41a514e9a7dae9ace2119dcb833d8be92c85b9c8eda1bf6fe78 [trunc 2 bit]

4f8370c60bdd3cfce5e26d5c4af927ded9ba4ebd04b3ad4fbfc10b518ec7f5 [all length]
4f37c60bd3cfe5e26d5caf927ded9ba4eb043ad4fbfc0b518ec7f5 [trunc 2 bit]

967f411a51e4e9ac7dae9ace52119dcb833d8bec92ac85b9c8e0da1bf6fe78 = AQäé¬}®ÎRË=ì¬¹ÈàÚöþx
4f8370c60bdd3cfce5e26d5c4af927ded9ba4ebd04b3ad4fbfc10b518ec7f5 = OpÆÝ<üåâm\Jù'ÞÙºN½³O¿ÁQÇõ

That's not right... Let's try hex-wise calculations...

96 - 4f = 47
837 - 7f4 = 43

Are we on to something? Hmm... I am lazy and thus made a script that would do all these for me!

./script.py
1000001 / 1000001 completed
FLAG: GCTF{5h4-rry_5h4-rry_n16h7}

CTF Writeups

GryphonCTF_2016: Anomaly

Write-up