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Background

NOC +10 intro

Since March 6th, 2015, a YouTube channel called Noc +10 has been uploading puzzle videos about once a week. Each video begins with the same introduction, followed by some form of clues which can be decoded to point to a hidden video's YouTube ID.

The hidden videos have had a nautical theme, possibly related to Naval Operation Concept 2010, but haven't presented any clear puzzles, aside from whatever meta puzzle or story is being told.

This question provides a writeup of the first five videos, and it's primary answer solves the fifth to reveal the sixth.

After that, three very strange videos that broke the pattern were posted, but they contained no apparent puzzles. I choose to ignore them for the time being.

7. Fourth contact - March 30, 2015

0101 0101 0000 0111

ISL 4 9 xEFTvZ

The seventh video, which is numbered sequentially in binary with all the others, begins with the NOC +10 logo and the same music playing in the background. At the halfway point, it switches to displaying the text ISL 4 9 xEFTvZ while playing a new song, identified as "Air On the G string", August Wilhelmj's arrangement of a piece by J. S. Bach.

As before, we can expect the text displayed to decode to a eleven-alphanumeric-character YouTube video ID.

According to Wikipedia, the song is most notable for Wilhelmj's arrangement, which allowed him to play the entire piece on just the G string of his violin. I suspect that that means that the letter G is a major factor in the decoding, although I'm not sure how.

I've tried shifting the letters by 'G' (like with the Caesar cipher in the first video), as well as several operations on the ASCII values involving G, but nothing has led to an active video ID.

Can you crack the last video's code and find the ID of the next one?

Other links:

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Bobson
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    As I already commented in Youtube, "AIR ON G STRING" can be interpreted as "AIR 1 6 STRING" or something similar. – leoll2 Apr 08 '15 at 12:25
  • Could it be a Vigenere cipher, using "AIRONGSTRING" (or something similar) as a key? – GentlePurpleRain Apr 08 '15 at 14:58
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    Well written question, I was frightened by the chance of someone posting a sequel in some crappy format which wuouldn't have fit my previous question. Good job :) the story goes on... – Marco Bonelli Apr 09 '15 at 11:12
  • Why is the text arranged in this particular way "ISL 4 9 xEFTvZ"? Shouldn't it mean something? – Rav Apr 10 '15 at 02:45
  • This may be a music related code. i.e. the difference in the two songs. – the4seasons Apr 11 '15 at 13:16
  • Also, are there supposed to be 4 extra letters/numbers? – the4seasons Apr 11 '15 at 13:26
  • @Rav - My guess is that spacing is significant, since there's such a big gap between the 4 and the 9. But it could be a red herring. – Bobson Apr 12 '15 at 01:27
  • @the4seasons - 4 extra where? Or are you saying that there's four missing? I think the gap is wide enough to fit four, but they're definitely not apparent in the video. – Bobson Apr 12 '15 at 01:27
  • There are 16 characters in the code but there should be lesser characters. The hidden video requires some characters to be taken out. – the4seasons Apr 13 '15 at 13:01
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    Is it of any significance that the binary 0101 0101 = U and 0000 0111 = BEL, http://en.wikipedia.org/wiki/Bell_character

    BEL can be referred to as control-**G** or ^**G** in caret notation. So yes G is very important. but for what...

     – Vincent Apr 14 '15 at 09:07
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    @VincentAdvocaat - Ooooh. It's certainly possible. The videos have been numbered sequentially (in binary), so I didn't pay any attention to that. But that is an interesting (and possibly relevant) coincidence. – Bobson Apr 14 '15 at 12:40
  • Next video !

    I hope this can help us a little more.

    https://www.youtube.com/watch?v=ow25RhBEips - Massi

     – Mark N May 29 '15 at 14:57
  • A new video has been posted! – justhalf Oct 10 '16 at 05:23
  • @justhalf - If it's got a puzzle in it, I encourage you to post a "Part 3" post, recapping everything to this point. I stopped following this particular puzzle a while ago since it didn't seem to be going anywhere, so I don't have any context for this newest one... if it's even got a puzzle in it (since it only has a 2-byte name instead of a 4-byte one). – Bobson Oct 10 '16 at 05:32

2 Answers2

9

The mystery has finally been solved!
The answer is:

hOH49oVWKmQ

Explanation:
The encrypted text is actually "lSL 4 9 xEFTvZ" and not "ISL 4 9 xEFTvZ" (the difference is in the first letter, which is lower-case L instead of upper-case i).
The code is then easily decrypted shifting back the first block of letters by 4, the second block by 9 and keeping intact the two numbers.
The result is:

hOH49oVWKmQ

As you can see, the main difficulty was in the interpretation of the first character (absolutely impossible to tell from the video). The cipher itself wasn't too hard (just two Gronsfeld ciphers).

leoll2
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This is not the definitive answer!

This is just a summary of the information we got about his last video, a list of failed attempts and potentially relevant elements for new approaches.

Elements contained in the video:

  • The name of the video: 0101 0101 0000 0111
  • Usual intro music
  • Suite No. 3 in D major by Johann Sebastian Bach, also known as "Air on the G string"
  • The string "ISL 4 $ $ $ $ 3 xEFTvZ"

Analysis of these elements:
The name of the video is, as usually, a binary number. Title numbers are always consecutive, in this case 0101 0101 0000 0111, which means 5507 in decimal. There seems to be no hint in the title.
As well, we have the typical intro music, basically NOC's signature. No info here!
Then we listen "Suite No. 3 in D major". What may be useful in it? Well, we have the number 3 and the capital letter D, but those information appear to be pretty irrelevant.
The real information is likely to be in the second name of that music, which is "Air on the G string". The words "Air" and "string" have the same length of "ISL" and "xEFTvZ", suggesting a direct correspondence between them.
Also, the word "On" could be interpreted as "1" (ON=1, OFF=0), so both strings can be perfectly aligned now. What about the "G"? When written in lower-case, "g" tends to be visually similar to the number "9", even though this appears captious.
Well, know we have the nucleus of the puzzle, the string ISL 4 $ $ $ $ 3 xEFTvZ.
The most notably features of this string are the presence of exactly 11 alpha-numeric characters, as in all Youtube videos ID (a video ID is what we actually expect to find), the sentence "IS LEFT Z" formed by the capital letters, an insolit separation between "4" and "3" (my ruler shows that it's made of 3 blank-spaces). As suggested before, these words align pretty well with the title of the music. Someone also pointed out that exactly 11 notes are played in the music. This might be a great hint, if confirmed!

Possible strategies:
It's almost obvious that we have to deal with a cipher, as we already did earlier. A Caesar's cipher would be too trivial, we've already solved that kind of cipher in a previous video.
Vigenere cipher is the top candidate to solve this mystery, since we are dealing with two strings of similar length.
Do we have to add or subtract the strings? We don't really know, try both!

Encrypted text:
"ISL 4 $ $ $ $ 3 xEFTvZ"

Potentially useful keys:
AIR 1 G STRING
AIR 1 9 STRING
AIR ? ? STRING where ? means any number/letter between 0-9/A-Z. This generalizes the AIR STRING approach.
AIRAIRAIRAIRAIRAIRAIRAIRAIR

Also, the 11 notes in the video could be a key, if only we could find their names.

What if nothing of this works?
Well, we would definitely need a new idea! We also might need to dig into his 3 previous public videos, looking for additional hints.

What can I do to help? First, you have to officially verify that Caesar's cipher doesn't work at all. It requires only 26 attempts, if you do it please confirm its non-validity in the comments. Then, hoping that you have a discrete experience with programming and coding (especially PHP) you could brute-force all the Vigenere keys suggested above and check if that video exists. Please be accurate, a minor mistake in your code is likely to miss the ID we're looking for! Also, if you have time to waste (or your pc has), apply Caesar to all the ID you got and verify them as well! If you're experienced with music, please verify that the played notes are 11. If you are able, identify them!

Sources and credits:
My reason, comments below the video, this discussion. Thanks to Ian MacDonald for noticing the 11 notes.

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leoll2
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    No. 3 in D major by Johann Sebastian Bach is actually simply known as Air. Air on the G string is an arrangement of this piece done by August Wilhelmj. – Ian MacDonald Apr 16 '15 at 17:35
  • Thanks for the clarification. Anyway, that's the most used name for that music by common people – leoll2 Apr 16 '15 at 17:37
  • No i think Ian might be right, people might confuse it and such a confusion is not something noc+10 seems to use. ian is indeed right august wilhelm TRANSPOSED Johan Sebastian Bach's "Air" to C Major and this allowed him to play the entire piece on his G string (something like that at least, i'm parafrasing from wikipedia) so Air on G string is a transposed song, so if someone knows a way to apply a transposition cipher to this, be my guest :) – Vincent Apr 16 '15 at 17:44
  • Are you sure the cypher key isn't the names of the 11 notes played in the clip? – Ian MacDonald Apr 16 '15 at 17:54
  • The notes are 11? Very interesting? Do you know them? – leoll2 Apr 16 '15 at 18:01
  • @IanMacDonald - You're right! It's hard to tell, because of the distortion breaking some notes in half, but there are only 11 notes played. I can't read sheet music, unfortunately, but I suspect those 11 notes might be part of our key – Bobson Apr 16 '15 at 18:58
  • CCFDBAGAGFE could be the notes, but it really depends on the key that the violin is using. – Ian MacDonald Apr 16 '15 at 21:33
  • @IanMacDonald If the played version is exactly the version arranged by August Wilhelmj the key would be C major. – ProGlockner Apr 20 '15 at 06:57
  • @VincentAdvocaat i tried Rail Fence cipher with 4 height, and Route cipher with 4x4 block, but both doesn't work – wuiyang Apr 20 '15 at 10:12
  • your encryption key is wrong, should be 9, not 3 – wuiyang Apr 23 '15 at 07:02
  • I'm not sure that the notes played are indeed 11, compare the video with the sheet music and you'll notice that the notes played are 14. – Narmer Apr 23 '15 at 08:08
  • https://www.youtube.com/watch?v=0bN5tOhFbBw links to the most recent upload from the channel - while I'm basically useless at crypto-stuff, I've been following along eagerly. Is this the fifth video in the same sequence, and if so, did someone discover the answer to the fourth video and I just missed it? – Bailey M May 06 '15 at 14:48
  • @BaileyM - No, that's another out-of-sequence one. I can't tell if it actually has a puzzle in it, or if it's just meta-plot related (like the other 0101 0101 puzzles). – Bobson May 21 '15 at 23:15
  • @BaileyM - On the other hand, the just-posted 0101 0101 0000 1000 video does appear to be a new puzzle video. – Bobson May 26 '15 at 04:10