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This is part of The Twenty Doors series.
The previous one is The Twenty Doors (ROOM 9)

There is some paper taped to the door in Room 10:

Well done! You are now halfway! To mark this event, this cipher is EXTRA hard!

- ???

You then look at the main paper

PART ONE

To decrypt the first cipher, I've given you a mathematical equation:
$d(x) = a-1(x - b) \mod\ m$
a is 11, b is 25, and d is the decrypted text.

Izea ahx lprp z cjrqg hjay mx rdrp, kla ja pazeap hjay nexmp.

mmking solves it without dying, so you get to Part 2:

PART TWO

Everyone loves a mime. MDEwMDEwMDAwMTAwMDAxMDEwMTAwMDAxMDAwMTExMDAxMDE= The other key is key. Wmb wmmuh, drh imqfo tdvw ubonbv lcfkmod rr d vdqirp vrzugb isu bbd jbqbvdwmsr, fqh nv kmvwxfooc xrgudgbdgoc. Jr wr qc kbgwnwb, kmwmx pc rdpb. Wmbub, csx empo imqi wlb frwkbv.

PART TWO - HINT ONE

'My name' refers to something recent in The Twenty Doors series, but not this part. Go back through each one, see if you can find something useful...

As requested, here is the contents of the site page.

My name again. J2I. Pga torooapr fpi Rlis Mcrcl ym otmplx tv Gsic 10. Iepzve aud hb, cap pbqi hb dnui ub. Befud. I hate vowles, exept for i.

PART THREE

CodeNewbie is still working on getting at the password, but here is the ciphertext:

Irrt sthcgma

Also, like magic, a keyboard appears, with the letters A to Z on it!

PART 3 - HINT 1

! Spinny! @HHF G L\NFHP301 3@WDXECT R1T0||0T GTFDHPSRX5R 3ARHCU/ £A NT S0! If you can be bothered to decode that, you've then got to work out my L3etspeak. :) It's Markdown O'clock!

PART 3 - HINT 2

L3etspeak is usually written with two three's (L33tspeak). So, what could that three mean???

There are going to be three separate parts to Room 10, thus it is a semi-interactive puzzle. The next part will be added when this door is solved!

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  • $\begingroup$ Maybe you could give a hint for the second part... I've tried going to your site /Kslkgh /george /gibson /my_name /georgegibson with a few different extensions (php, html, htm) and also without extensions and came up with nothing... Also couldn't find suspicious looking links in it's html source code... $\endgroup$
    – Davide
    Aug 5, 2015 at 8:47
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    $\begingroup$ @Davide This name has only been coming up recently, and only on puzzling. Look back through The Twenty Doors. $\endgroup$
    – user9377
    Aug 5, 2015 at 8:55
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    $\begingroup$ @Kslkgh so why does it say we are halfway now? :P $\endgroup$
    – Andrew Smith
    Aug 5, 2015 at 19:24
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    $\begingroup$ So... Where was that page? $\endgroup$
    – LeppyR64
    Aug 7, 2015 at 15:54
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    $\begingroup$ Where did that Part 3 cipher text come from? $\endgroup$
    – Davide
    Aug 11, 2015 at 8:42

5 Answers 5

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The OP added the following sentence in this comment:

Here's a hint, because I'm getting bored of waiting:
ahhltomot eiXect fcu eutnsr ee lnfhqso SPUN THREE TIMES!

This is a 3 column transposition cipher. After some manual adjustment, this decodes to:
Search the left column of the question

Part 3, Hints 1&2 - This is also a 3 column transposition cipher. After some manual adjustment and translation from Leetspeak, this decodes to:
Search the far right left column of the page to find the password

Part 3 - Based on the hints: "all up, not down", "left column", "(markdown) format read", "except for lines that are >Quoted or >!Spoilers", "eleven characters (not a word)", and "forget the stars", the password is:

pTCPAPmYTTT

Final Answer - By subtracting this password from the ciphertext (irrt sthcgma), the final answer is:

type seventh

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  • $\begingroup$ Reach should be read. Sorry. $\endgroup$
    – user9377
    Aug 16, 2015 at 6:22
  • $\begingroup$ This hint is for a different question, isn't it? $\endgroup$
    – Davide
    Aug 18, 2015 at 11:06
  • $\begingroup$ @Davide Nope, the hint is for this question. $\endgroup$
    – user9377
    Aug 19, 2015 at 6:41
  • $\begingroup$ @Len Your getting warmer. Try broadening your search along that column. $\endgroup$
    – user9377
    Aug 19, 2015 at 6:50
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    $\begingroup$ Maybe you could TRY typing in PACNTRT $\endgroup$
    – Davide
    Aug 20, 2015 at 16:35
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Part Two:

Using the plaintext provided from the site,

My name again. J2I. Pga torooapr fpi Rlis Mcrcl ym otmplx tv Gsic 10. Iepzve aud hb, cap pbqi hb dnui ub. Befud. I hate vowles, exept for i.

We need to break up this text to arrive at a solution:

My name again.

This points to the name 'Dr. X' that the OP used for himself in Room 8.

J2I. Befud.

This tells us that the encrypted text in between uses a Bifid cipher with J converted to I. So decrypting the encrypted text with the translation 'I to J' and 'DRX' as the key gives us

The password for Part Three js hjdden jn Room 10. Search all up, not down to fjnd jt.

I hate vowles, exept for i.

Using this clue, we get the line

The password for Part Three is hidden in Room 10. Search all up, not down to find it.

Still working on the riddle...

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  • $\begingroup$ Isn't there usually a keypad with some characters where we have to key in the answer? I don't see anything in this room. $\endgroup$
    – CodeNewbie
    Aug 7, 2015 at 7:29
  • $\begingroup$ Um... Yeah. Fixed. $\endgroup$
    – user9377
    Aug 10, 2015 at 12:31
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Part one

Using an

affine cipher with a = 11 and b = 25,

the text decodes to

Part two uses a field with no eyes, but it starts with grons.

So part two will use a

grons + field - i = gronsfeld cipher

Part two

Converting MDEwMDEwMDAwMTAwMDAxMDEwMTAwMDAxMDAwMTExMDAxMDE=

from base 64 to ascii

gives you

01001000010000101010000100011100101

Using this as the cipher key and "key" as the alphabet key, you get

The third, and final part relies heavily on a random source for key generation, and is virtually uncrackable. Go to my website, visit my name. There, you will find the answer.

CodeNewbie got the next piece. Looking at the website and decoding the string of text found there, you get

The password for Part Three is hidden in Room 10. Search all up, not down to find it.

Looking up at the question and searching in the markdown, there's a line commented out that says

ignore this line

Not sure of its significance however...

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  • 1
    $\begingroup$ Correct! Part two will be here soon! $\endgroup$
    – user9377
    Jul 31, 2015 at 19:08
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    $\begingroup$ Finished part two. $\endgroup$
    – mmking
    Jul 31, 2015 at 19:19
  • $\begingroup$ No, you haven't quite yet. Have you not taken the advice from your decryption? $\endgroup$
    – user9377
    Aug 1, 2015 at 6:51
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    $\begingroup$ @Kslkgh I believe mmking has gone as far as required. Requesting a user from StackExchange to visit a third party website to solve a puzzle seems like it would be out of the scope of puzzling.SE. (For both computer safety reasons and site policy) $\endgroup$
    – Mark N
    Aug 6, 2015 at 17:04
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    $\begingroup$ Is the latest revision important in any way? $\endgroup$
    – mmking
    Aug 15, 2015 at 14:17
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Part 2:

Decoding the first message (MDEwMDEwMDAwMTAwMDAxMDEwMTAwMDAxMDAwMTExMDAxMDE=)

with base 64

We get:

01001000010000101010000100011100101

Which is the cipher key for the Gronsfeld cipher (see mmking answer). The other key is "key"

So the second message decoded is:

The third, and final part relies heavily on a random source for key generation, and is virtually uncrackable. Go to my website, visit my name. There, you will find the answer.

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  • $\begingroup$ Did you finish this before mmking? $\endgroup$
    – user9377
    Aug 1, 2015 at 6:52
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    $\begingroup$ I think so. Like one minute before (max) $\endgroup$
    – TroyAndAbed
    Aug 1, 2015 at 10:31
  • $\begingroup$ So, you did this in at most 30 minutes, and mmking in 31 minutes. Noice. $\endgroup$
    – Klyzx
    Aug 4, 2015 at 17:10
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Searching this room for all up and not down, as the last riddle suggested, I'd say the password is

EXTRA which is in all uppercase letters in the original piece of paper

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1
  • $\begingroup$ Sorry, but it's not that. $\endgroup$
    – user9377
    Aug 9, 2015 at 7:34

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