Peterhead Codes and Ciphers Club: Weekly Challenge II

Question

This is another cipher-based challenge I created for my club. The story you uncover is generated from Crusader Kings II. The events of this challenge precede those of the Reverse Engineering challenge.

Members of the club have to search the library for a book on Scottish architecture, but since you can't do that, I am showing you a scan of the relevant page.

This is the journal of Chief Broichan of Buchan.

AD 769

January 12

The day of my marriage to Eadburh, the daughter of the petty king of Kent.

January 29

A madman accosted me today. Called me "The Inventor". Claimed to be from both the future and the past. Said something about a book on Scottish architecture. Gave me a note with peculiar scrawls on it, and a map of a country I don't recognise.

February 15

My spymaster, a lowborn named Rudri, has provided me with an ingenious technique for obscuring messages. He recommends that I use it for the more sensitive entries of my journal.

March 24

A skilled diplomat by name of Fothad has approached me with his services in return for one day pressing his claim on a piece of a large island to the west. isvn ikts sawa itse aoha aerp tnod eess ngre atnh hteh yltn ttbo wsww omeh outd. He will replace my Chancellor, Bishop Bili of St Machar, who has all tcoua gulle rmede hofnk sdura.

March 27

I heard Bishop Bili cursing me aloud today. Hopefully this doesn't develop into anything serious. I will name him Master of the Horse to placate him.

May 8

isrwrgo nmoraym nbdaate vahkfii aclaiia aeddeot catfhth.

June 13

During this evening's council meeting, Marshal Caruorst told us of a local rumour of an artifact hidden not far away from here. I have ordered Caruorst to arrange a search.

Page 425 of The Castellated and Domestic Architecture of Scotland, Vol V

The note that the madman passed to Broichan

The other side has the following messages:

The key is E1E2L3I4.

The key opens two locks in two different ways.

SEIO PUNZ IRRV DBQS XSCU

NGVV PLKU JGJR SGTG CKRH SOGQ ENGY FUTH MGHH MOTF PSSR O
LEAF LEAF LEAF LEAF LEAF LEAF LEAF LEAF LEAF LEAF LEAF L

Answer 1

I have not solved this part of the puzzle, nor have I made sense of the flowers in the madman's note:

The key is E1E2L3I4.

The key opens two locks in two different ways.

SEIO PUNZ IRRV DBQS XSCU

To solve the ciphertexts within the journal entries:

1. isvn ikts sawa itse aoha aerp tnod eess ngre atnh hteh yltn ttbo wsww omeh outd
2. tcoua gulle rmede hofnk sdura
3. isrwrgo nmoraym nbdaate vahkfii aclaiia aeddeot catfhth

These are all written in equally-sized groups, and in fact the length of each one is a square. Try writing the first one into an 8x8 square by rows.

isvnikts
sawaitse
aohaaerp
tnodeess
ngreatnh
htehyltn
ttbowsww
omehoutd

Note the awaits on the second line, great on the fifth line, and a reversed dont on the fourth line. This is characteristic of unkeyed route transpositions which leave fragments of plaintext intact. After a few short trials, the route is found: The plaintext was written into the grid by rows, and read out by a counterclockwise spiral starting from the top-left. To decipher, write the ciphertext in by a counterclockwise spiral:

i    ...
s      .
v      a
n      h
i      o
k      a
t      e
ssawaits

idontpre
sentlyha
vethemea
nstodoth
isbutwho
knowswha
tgreatne
ssawaits

The plaintext is evident on the rows. The other two ciphers are found to use the same method, and all three of them read:
1. (pressing his claim...) I don't presently have the means to do this, but who knows what greatness awaits.
2. (who has all) the decorum of a drunk seagull
3. (May 8) I have tasked dear Fothad with fabricating a claim on Moray.

To solve this line:

NGVV PLKU JGJR SGTG CKRH SOGQ ENGY FUTH MGHH MOTF PSSR O

It is effectively a Vigenere cipher with a four-letter key. Boxentriq's autosolver deciphers the text and recovers the key BGGD:
Maps of Eriador and Beleriand have one label in common
Working backwards, the key BGGD represents the Caesar shifts 1, 6, 6, 3, which is represented by the year 1663 in the upper emblem on Page 425. This emblem resembles the LEAF emblem on the madman's note, so the intended solution was to map the letters LEAF to 1663 using the note and the page and then decipher the text by undoing those Caesar shifts.