Challenge 6B foxed a few of you! It was indeed, as described in the forums early this morning by JohnatCCO:
"two monoalphabetic substitutions, mixed:
- upper-case letters with the keyword 'MONHIER';
- lower-case letters a special affine shift called 'Atbash', which effectively reverses the alphabet."
Some very ingenious ideas about how to crack it out there. I particularly liked this from hkbm:
"In the 19th and 20th 5-letter groups of 6B, you will find OzOyz. It occurred to me that if the capitals and lowercase were each each encrypted by a different cipher, then "OzOyz" might be "babba", i.e. the start of Babbage. I found this by realising that "Babbage" could be a crib, and searching for possible occurrences of it. Indeed, I was correct with my assumption that "OzOyz" was "babba", and that helped me to crack 6B by 16:48:02 on the day it came out."
Congratulations to the winners of the prizes for Challenge 6A:
Throat Nanny Who from Harrow Way
Nick, Jacob, Louis, Harry, Dobbo, Heather, Christine, Camel. Ciera, Elloise and Ivor from Bartholomew School
Laura, Holly and Sophie from Kingsway
Helen Wickins from Alcester Grammar School
Brittany Ulm from Cedars Upper School
Engimatic2 from Walton High
George Williams and Alice Williams from Redruth School
Tereasa Thomas from Christopher Whitehead Language College
I am frankly disappointed, you found Challenge 7 far too easy! Anyway maybe Challenge 8 will make up for it!
Congratulations to all of you, I am amazed at how many are still in the running for the top prizes and I wish you all luck in this year's final challenge. I hope you enjoy it. There will be news about the Prizegiving published soon - we have great speakers lined up and I look forward to meeting some of you there.
Congratulations to the winners of the prizes for Challenge 7A:
Toby Dirnhuber, Charlie Dowding, Manuel Fernandez de la Fuente, Nino Freuler, Dong-Jae Hoang and Paul Song from Clifton College
Amylalala from South Wilts Grammar School
The IQ Club from Cardinal Allen Catholic High
Joe Rigbey and Anwen Pembery from Whitecross School
Katie from South Wilts Grammar School
Michael Brennan, Louise Tarleton, Mary Phillips, Jennifer Wallin, Ruth Hodges, Alice van den Bosch and Hannah De Souza. from St. Peter's Catholic Comprehensive
The cipher king from holly-hall
Peter Nugent, Jayen Raghvani, Heena Chotai, Imen Zoubir and Jiten Bhatia from Preston Manor High School
Well done to everyone this week. Did you spot that Monhier's message to Lord Pennylaine was encrypted using a keyword substitution using the keyword FRANCE? He may be a treacherous enemy of the British Empire, but you have to admire his patriotism. A curiosity of the cipher this week was that the letters S, T, U, V, W, X, Y and Z were all substituted by themselves. Here is the substitution table Monhier used in part 3B:
| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
| F | R | A | N | C | E | B | D | G | H | I | J | K | L | M | O | P | Q | S | T | U | V | W | X | Y | Z |
And now the announcement you are all waiting for: here are the winners for this week's part A prizes:
| Keir Edwards, Tom Russell and Benjamin James from Queen Elizabeth's School Carl Martyres, Jonathan Hughes and Edward Rewse from The Kings School, Peterborough Example B from Our Lady's Catholic Primary School Meeting Place from Southend High Shcool (sic) for Boys Georgina Hughes from Harlington Upper School Matt, Ollie, Connor, Jack, Corey and Matt T from Bishop Milner Catholic School Claire Baily, Beth Hutchings and Beth Norris from Honiton Community College Jane, Tess, Abi, Hannah, Eilidh, Jack and Joe from Newminster Middle School
|
PS Harry might or might not be an alumnus of Westcliff High School for Boys, so he is delighted to see that the team from the old enemy, Southend High School for Boys can't spell School! This is a useful reminder to everyone to make sure their profile details are correct and complete.
Please do take a look at the points scheme for Challenge 3, you need to get your solution to 3B submitted by midnight tonight to get full marks! There is a link on the Challenge page which shows how they are to be awarded. All the best, Harry
Getting stuck on Challenge 2? I'm guessing the 5-letter blocks are confusing you in 2B. All that the sender has done is removed all the spaces and punctuation, and grouped the letters into blocks of five after encrypting it. It is a bit tougher because you can;t use word shapes to help you, but there are still things you can do.
1. Try to find the most common letter. It probably stands for E (or possibly T, they are the two most common letters in English)
2. Once you have found E see if you can find the word THE by looking for a common triple ending in the decrypted letter E
3. Try to guess what type of cipher has been used, Caesar shift? Affine shift? Keyword subsitution? If you guess right it is a LOT easier to crack. And given how early this is in the competition, it is more likely to be at the easy end of this list!
Do keep trying, you still have a couple of days to get your answer in.
All the best, Harry