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"Can You Find It?"

GCHQ ran another recruitment campaign/competition this year (2013), called “Can You Find It.”

I had a stab at it, and though I’d record the puzzles and solutions. I’ll hold off publishing until the competition closes on the 21st October.

Puzzle 1

AWVLI QIQVT QOSQO ELGCV IIQWD LCUQE EOENN WWOAO
LTDNU QTGAW TSMDO QTLAO QSDCH PQQIQ DQQTQ OOTUD
BNIQH BHHTD UTEET FDUEA UMORE SQEQE MLTME TIREC
LICAI QATUN QRALT ENEIN RKG

This is transposition cipher, with “Q”s substituted for blanks.

The big clue is in the frequency/histogram of the letters, which matches normal english, except for Q.

It’s 143 characters, which is 13×11. So try writing as a 13×11 grid:

A W V L I Q I Q V T Q O S
Q O E L G C V I I Q W D L
C U Q E E O E N N W W O A
O L T D N U Q T G A W T S
M D O Q T L A O Q S D C H
P Q Q I Q D Q Q T Q O O T
U D B N I Q H B H H T D U
T E E T F D U E A U M O R
E S Q E Q E M L T M E T I
R E C L I C A I Q A T U N
Q R A L T E N E I N R K G

Then read the columns
AQCOMPUTERQWOULDQDESERVEQTOQBEQCALLEDQINTELLIGENTQ
IFQITQCOULDQDECEIVEQAQHUMANQINTOQBELIEVINGQTHATQITQ
WASQHUMANQWWWDOTMETRODOTCODOTUKSLASHTURING

Which is pretty easy to translate into:
A computer would deserve to be called intelligent if it could deceive a human into believing that it was human www.metro.co.uk/turing

Puzzle 2

This links takes you to a download site, with a single file – “comp1.key”, the contents of which are:

-----BEGIN RSA PRIVATE KEY-----
MIIC2gIBAAKBgDfABK8+joDLdbFTDJ+y3PTTzkqCi1L2qEjgxdg1iyZshJTeKUck
SYVyKBeOBtB3FwwqXVa6iNEHJeLFewFE6ulEOIcatVp11Zg0ibMfnqTivbd6t8/z
3KzqrFksg9xQiicMactmTqFkm8ro5ODc2NTQzMjEwLy4tLCslBOCOVHxAgMBAAEC
gYATW12FB2BtQbecmSxh6rWjYENZRZhgdvoZS8oF9xlYfwdNtRF5/RR1/BwFia++
BAuBktgTu/KzORsjcNPzrd0uTCbTG6hW8YPK2ROVOOeAMHek8Nl3+SW5wdePKuWw
MdjDDjqxXDns+ZC1d2Cpz5V+x+2znOYL0bsEKei0sWl7LQKBgDfABK8+joDLdbFT
DJ+y3PTTzkqCi1L2qEjgxdg1iyZshJTeKUckSYVyKBeOBtB3FwwqXVa6iNEHJeLF
ewFE6uhVSior5HGPArFhsOQ0v9ob1NCV7P8M99qN4XplmX/xs05HgQCVh9aMWtio
pKCcmJSQjIiEgHx4dHBsU9JB+TvkAkB3dy53aHRzaXNpbGd1b2VjdHNyZWhzcmku
ZW9jdS4va2xidGVoY2VsIHkgICAgICAgICAgICAgICAgICAgIAuPAkATpSSd/C5S
IEAbUPk+ZYAdt7OYVzay7ViAiaukhkt+/sJG+m8GmHnAKyLf9ohx3/aIcd/2iHHf
9ohx3/ayirJPAkAIefJYEpdAoRjJQCHPGUpOVjLiyQMyPcnsutG+ctAGGU8lZTDU
yUim9V7iwqTE4sKkxOLCpMTiwqTE4sKkxOFNAoGAFInzTsAOkauW3crd1XfxMhxi
tUkapdQqlwvFhZuouNIybfEOfW6WkjtghBDyqf50cEFWXMJ7Vk8mr6cwTosPvYKU
VXKUCblretLTeU95TlbkprizPky++5b7pQuSi3mpLMi+6VgvcjTthfXPYNg2JjJp
gmteC4felYL/2FTAmT8=
-----END RSA PRIVATE KEY-----

This looks like an RSA private key, so first thoughts naturally resolve around decrypting something.

However it isn’t a valid key. Using OpenSSL to examine it, we discover:

$ openssl rsa -check -in comp1.key"
RSA key error: p not prime
RSA key error: n does not equal p q
RSA key error: d e not congruent to 1
RSA key error: dmp1 not congruent to d

RSA keys fundamentally consist of two prime numbers, and the fact that one isn’t prime is very suspicous. Let’s look at them.

$ openssl rsa -in "comp1.key" -text
modulus:
    37:c0:04:af:3e:8e:80:cb:75:b1:53:0c:9f:b2:dc:
    f4:d3:ce:4a:82:8b:52:f6:a8:48:e0:c5:d8:35:8b:
    26:6c:84:94:de:29:47:24:49:85:72:28:17:8e:06:
    d0:77:17:0c:2a:5d:56:ba:88:d1:07:25:e2:c5:7b:
    01:44:ea:e9:44:38:87:1a:b5:5a:75:d5:98:34:89:
    b3:1f:9e:a4:e2:bd:b7:7a:b7:cf:f3:dc:ac:ea:ac:
    59:2c:83:dc:50:8a:27:0c:69:cb:66:4e:a1:64:9b:
    ca:e8:e4:e0:dc:d8:d4:d0:cc:c8:c4:c0:bc:b8:b4:
    b0:ac:94:13:82:39:51:f1
publicExponent: 65537 (0x10001)
privateExponent:
    13:5b:5d:85:07:60:6d:41:b7:9c:99:2c:61:ea:b5:
    a3:60:43:59:45:98:60:76:fa:19:4b:ca:05:f7:19:
    58:7f:07:4d:b5:11:79:fd:14:75:fc:1c:05:89:af:
    be:04:0b:81:92:d8:13:bb:f2:b3:39:1b:23:70:d3:
    f3:ad:dd:2e:4c:26:d3:1b:a8:56:f1:83:ca:d9:13:
    95:38:e7:80:30:77:a4:f0:d9:77:f9:25:b9:c1:d7:
    8f:2a:e5:b0:31:d8:c3:0e:3a:b1:5c:39:ec:f9:90:
    b5:77:60:a9:cf:95:7e:c7:ed:b3:9c:e6:0b:d1:bb:
    04:29:e8:b4:b1:69:7b:2d
prime1:
    37:c0:04:af:3e:8e:80:cb:75:b1:53:0c:9f:b2:dc:
    f4:d3:ce:4a:82:8b:52:f6:a8:48:e0:c5:d8:35:8b:
    26:6c:84:94:de:29:47:24:49:85:72:28:17:8e:06:
    d0:77:17:0c:2a:5d:56:ba:88:d1:07:25:e2:c5:7b:
    01:44:ea:e8:55:4a:2a:2b:e4:71:8f:02:b1:61:b0:
    e4:34:bf:da:1b:d4:d0:95:ec:ff:0c:f7:da:8d:e1:
    7a:65:99:7f:f1:b3:4e:47:81:00:95:87:d6:8c:5a:
    d8:a8:a4:a0:9c:98:94:90:8c:88:84:80:7c:78:74:
    70:6c:53:d2:41:f9:3b:e4
prime2:
    77:77:2e:77:68:74:73:69:73:69:6c:67:75:6f:65:
    63:74:73:72:65:68:73:72:69:2e:65:6f:63:75:2e:
    2f:6b:6c:62:74:65:68:63:65:6c:20:79:20:20:20:
    20:20:20:20:20:20:20:20:20:20:20:20:20:20:20:
    20:20:0b:8f
exponent1:
    13:a5:24:9d:fc:2e:52:20:40:1b:50:f9:3e:65:80:
    1d:b7:b3:98:57:36:b2:ed:58:80:89:ab:a4:86:4b:
    7e:fe:c2:46:fa:6f:06:98:79:c0:2b:22:df:f6:88:
    71:df:f6:88:71:df:f6:88:71:df:f6:88:71:df:f6:
    b2:8a:b2:4f
exponent2:
    08:79:f2:58:12:97:40:a1:18:c9:40:21:cf:19:4a:
    4e:56:32:e2:c9:03:32:3d:c9:ec:ba:d1:be:72:d0:
    06:19:4f:25:65:30:d4:c9:48:a6:f5:5e:e2:c2:a4:
    c4:e2:c2:a4:c4:e2:c2:a4:c4:e2:c2:a4:c4:e2:c2:
    a4:c4:e1:4d
coefficient:
    14:89:f3:4e:c0:0e:91:ab:96:dd:ca:dd:d5:77:f1:
    32:1c:62:b5:49:1a:a5:d4:2a:97:0b:c5:85:9b:a8:
    b8:d2:32:6d:f1:0e:7d:6e:96:92:3b:60:84:10:f2:
    a9:fe:74:70:41:56:5c:c2:7b:56:4f:26:af:a7:30:
    4e:8b:0f:bd:82:94:55:72:94:09:b9:6b:7a:d2:d3:
    79:4f:79:4e:56:e4:a6:b8:b3:3e:4c:be:fb:96:fb:
    a5:0b:92:8b:79:a9:2c:c8:be:e9:58:2f:72:34:ed:
    85:f5:cf:60:d8:36:26:32:69:82:6b:5e:0b:87:de:
    95:82:ff:d8:54:c0:99:3f

Run each part through a hex decoder, and you get gibberish except for prime2 (notice all all the repeated 0x20s at the end of prime2, and 0x20 just happens to be the ASCII code for space.)

Let’s decode prime2 from hex into ASCII using http://www.dolcevie.com/js/converter.html

ww.whtsisilguoectsrehsri.eocu./klbtehcel y

This looks a lot like a web address to me, with a bit of endian stuff going on. Switch around each pair of bytes:
www.thisisgloucestershire.co.uk/bletchley

Puzzle 3

2910404C21CF8BF4CC93B7D4A518BABF34B42A8AB0047627998D633E653AF63A873C\
8FABBE8D095ED125D4539706932425E78C261E2AB9273D177578F20E38AFEF124E06\
8D230BA64AEB8FF80256EA015AA3BFF102FE652A4CBD33B4036F519E5899316A6250\
840D141B8535AB560BDCBDE8A67A09B7C97CB2FA308DFFBAD9F9

Very clearly a hex stream, but full of non-ascii characters. Convert it anyway and you get nonsense.

At this point I needed a little nudge. Because I knew the RSA key from puzzle 2 was broken, it didn’t even occur to me to use it to decrypt this, although in retrospect in seems very obvious. I’d tried using the key with openssl trying to solver puzzle 2, and it was no go.

The nudge pointed me to the site below, where it transpires you don’t actually need the 2 primes, just the public modulus, public exponent, and private exponent.
http://nmichaels.org/rsa.py

Stick these values in from the key, together with the hex string, and what happens:

0x20 0x20 0x20 0x20 0x20 0x20 0x20 0x20 0x77 0x77 0x2e 0x77 0x68 0x74 0x72 0x65 0x67 0x65 0x73 0x69 0x65 0x74 0x2e 0x72 0x6f 0x63 0x75 0x2e 0x2f 0x6b 0x6e 0x65 0x67 0x69 0x61 0x6d 0x30 0x32 0x33 0x31 0x20 0x20 0x20 0x20 0x20 0x20 0x20 0x20

Oo, now I recognise the 0x20 (space), and the 0x77 0x77 0x2e 0x77 sequence (“ww.w”) from puzzle two – lets go back to ascii:

ww.whtregesiet.rocu./knegiam0231 

Switch the pairs again:
www.theregister.co.uk/enigma2013

Puzzle 4

This one’s a picture!

comp3

Obvious guess is that there’s something encoded in it.
Standard first step is to check the HTML page source and URL, no clues there. No mouseover magic or anything like that (there hasn’t been so far) – it’s just an image.
I’m also assuming that the picture itself isn’t the answer.

Let’s look at the EXIF. Nothing there.

Two choices – one is there’s some visual data, two is there’s digital data encoded somehow.

No joy with fiddling with brightness, contrast, or shifting images around.

JSTEG may be promising – download, patch, compile, extract and we get:

9e34 fb8d 8f1e 4a00 e45f 2d63 057d 7dd8
37b9 cf09 68d5 8ff7 d788 6c3c 3d25 70ad
f078 1b6c 5753 b898 77f9

Nonsense in ASCII – maybe need to decode it using our RSA key? Nope – still nonsense.

Steghide looks good, but we need a passphrase. Nothing obvious works though (“turing”, “enigma”, “enigma2013”, “bletchley”, “GCHQ”, “lovelace”).

Because it’s a JPEG, the image hiding options are limited.

What about the image structure of a JPEG – it runs from a Start of Image (0xFF,0xD8) to an End of Image (0xff,0xD9), and in theory you can put stuff in the file after the End Of Image marker. This particular file has 2 SOIs and EOIs – so two images, running from 0x0 to 0xcbd3 (52180) and 0xcbd4 to 0xf404?

So, let’s skip the first 52180 bytes, and put the rest into a new jpeg:

%> dd bs=1 skip=52180 < comp3.jpg > comp3b.jpg

See if it’s promising:

%> identify comp3b.jpg
comp3b.jpg JPEG 451x97 451x97+0+0 PseudoClass 256c 8-bit 10.0469kb

Sure looks like an image – shall we view it?
comp3b

Yay – off to www.eveningstandard.co.uk/colossus

Puzzle 5

Strange.

Text is just

CanYouFindIt.co.uk/secured

With a bit of fancy wibbling.

Clicking it takes you back to the first puzzle page, and the answer is exactly as expected.

So that’s that!

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