Passcode Decoding Walkthrough #011.1 Verum Inveniri Solutions

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(Re)Introduction to passcode solving

A few weeks ago, Verum Inveniri made a post on Google+:

We encourage all new Agents to learn cryptographic principles, some of which we have published in a series of posts:

Steganography
https://plus.google.com/109846653838501599116/posts/1HAZCCCrhcf

Substitution
https://plus.google.com/109846653838501599116/posts/ifNptGN7igo

Transposition
https://plus.google.com/109846653838501599116/posts/Mf2mzNxCtQ1
https://plus.google.com/109846653838501599116/posts/bcVJoDJ8bTH
https://plus.google.com/109846653838501599116/posts/4GqqJemK9au

If you’re actually interested in solving them, click the links and give them a try without the solutions.

The following codes are now Fully Redeemed:

6zh6codep8t4z
8xc2substitutionz4t7p
8ye3transpositionu2p9y
6qd7cryptoz4u8s
4zh4cipherz4s8v

The passcodes are in the following format:

[2-9][p-z][a-h][2-9]keyword[p-z][2-9][p-z][2-9][p-z]

Steganography

The post suggests to increase the contrast and decrease the brightness of the image to reveal the code:

contrast

Looking at the bottom, we see something very faint:

6zh6codep8t4z

Substitution

Looking at the bottom of the image we see the substitution key. The long row of black symbols are the letters a to z, the row of black symbols just above that are the numbers 0 to 9, matching them up to the first two rows:

this/is/a/secret/message:
8xc2substitutionz4t7p

Transposition

The first link describes the Railfence cipher and presents a code that has been encoded with it:

8tsin9y3rnpstoupyeaoi2

Using the Rumkin website to aid us with railfence, Decrypting the cipher text with 3 rails:

8ye3transpositionu2p9y

The second link describes some other types of transposition and presents us with a 16 character block on the left:

4u8s
zotp
7cry
dqiv

The transposition used for this one is boustrophedon (snaking) from the top-right corner and reversal:

s8u4zotpyrc7dqiv

viqd7cryptoz4u8s

But that doesn’t produce a valid passcode yet! The passcode format is almost correct except the first part, which needs to start with a number. vi is the roman numeral representation of 6.

6qd7cryptoz4u8s

The last link has an image with a child’s writing of the cipher text:

4ceszir8hpzv4h4

The hint is subtlely inserted as 4 but the method to use is not railfence. After going through all the methods introduced in the second link, the proper method is skip (4):

4zh4cipherz4s8v

What’s next?

For the next post, we’ll be looking at the post that Verum Inveniri made after assembling the nominus dead drops and we’ll be revealing 3 more passcodes.

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Passcode Decoding Walkthrough #011.1 Verum Inveniri Solutions

by Jack Truong (SQL) time to read: 2 min
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