I started our second week of Bletchley Juniors Codebreaking Club with some pinprick codes. I had prepared by cutting out some newspaper articles and finding some jokes and punchlines that I thought the children would like. (“Why did the chicken cross the playground?” “To get to the other slide”. Admit it, that one is not that bad). The intention was to give one child the joke and another child the punchline. I used a pin to prick a hole above letters in the newspaper article which corresponded to letters in the joke.

I gave one article to the children and asked them to see how the message was hidden. None of them could: when you hold the article and look down you cannot see the tiny pinpricks. I asked the children to hold it up to the light. One child said they could see ‘sparkles’: when light is behind the newspaper each pinprick is revealed. However, things did not work quite as well as I had planned. When I tested this at home using my ceiling light fitting, it worked perfectly. But the light is very different in the school hall: the ceiling is much higher, the light fittings are different, and it was tricky for the children to see all the pinpricks. We went over to the doors, and were able to get just enough light through the windows (it is January) to read the messages, giving the children a bit of help. The lesson I learnt was to test things like this in the school environment first, as I cannot assume that something that works at home can be replicated in the school hall. On the other hand, the fact that the messages were hard to read does prove that the pinprick code is a useful way to hide a message from someone who does not know where to look for it.

The second part of the session used a book cipher. I had borrowed several copies of the same novel from Year 6. I had written a message for each child, then encoded the message as a book cipher. Each letter was encoded as a set of numbers e.g. 17, 3, 4, where 17 is the page number, 3 is the row, and 4 means count four letters along starting on the left. I wrote out the ciphers in a long list, one per row. After prompting them to write each letter out again along one row, each child was able to decode their message. I think they enjoyed having a message that was personal to them, based on their interests. We ended the session by reading out the jokes from earlier. I am pleased to report the chicken joke got the biggest laugh.

We introduced two new games at our Adult Board Games Club. The first was Foxy (MB, 1977). There is a 6 x 6 board, with 32 shallow holes (the corners do not have holes). There are 11 purple wooden discs, which are randomly distributed across the board. Each player has a tube which they fill with 11 wooden discs (one player has blue, the other yellow) and position on opposite corners. Players take it in turns to move their tube in any direction, over any number of spaces, but they cannot turn direction mid-move. As the tube moves over an empty hole a disc drops down. The first player to empty their tube is the winner. A good strategy is to try and block the other player’s tube with your own tube, limiting their options on their next turn. Our members enjoyed the mechanism of moving the tube across the board: this was quite different to any other game they had played.

The other new game was Push (Spears, 1977). This is another game about trying to work out the effect of moving a row. One player has the yellow balls, and the other player has the black balls. The winner is the first to make a 3×3 square of their colour. Players push the balls a row at a time, and they keep pushing rows as long as the ball that comes out is their colour; if not, the other player takes a turn. The same player won both the games we played, with their 3×3 square in the same position both times: what are the odds of that happening?

 

 

Bletchley Juniors Codebreaking Club opened its doors today for its first intake of codebreakers. I started with some steganography, explaining that it is an Ancient Greek word meaning “covered writing”. I asked for a volunteer. Every child put their hand up. I said it was lovely that they were all so keen, but they did not know what they were volunteering for! I then chose one child and asked them to come to the front. I explained that they had to act the part of a slave in Ancient Greece. They looked a bit doubtful, but gamefully carried on. I played the part of Histiaeus, and Anna played the part of Aristogoras, his son in law, who lived in different parts of Greece. We role-played me shaving the slave’s head and tattooing a message on their head. We then waited several weeks for the hair to grow back. I then gave the slave their instructions (they had to memorise a line) and sent them on their way to Aristogoras. When they arrived they said “shave my head and look thereon”. Aristogoras did this and read the message. The slave then had to wait for their hair to grow back again before they could travel home. I wanted to start with something quite light-hearted but which would also get the children thinking about the different stages to sending a message.

I then showed the children a scytale, a tool used by the Ancient Greeks to communicate during military campaigns.

I showed them one I made earlier. I unwound the paper to show that when you try to read down, the message makes no sense. I demonstrated that the person receiving the message must have a scytale of the same diameter, or the message cannot be read.

The children then had a go at making their own scytale using cardboard tubes and long strips of paper. They first had to plan and write their message on separate paper, to make sure it was the correct length. The wound their strip of paper around the tube, attached it with tape and wrote their message on it, putting one letter on each strip. They unwound their message and swapped it with another child, then tried to read and write down the new message. The children seemed to really enjoy the opportunity to use their hands and make something. We gave them spare strips of paper to take home if they wanted to, along with the tubes.

We ended by giving out log books I had made (and hand-stitched!). I asked the children to write in steganography and scytale as our two topics from the session.