It is nice to see Shakini smilingly happy as she helps out, wearing the same dress she's worn so far that matches the other maids in colour and style, but now it's hers and not borrowed, and she will have gotten another so that one can be cleaned and such. Shakini has been fairly robot-like, so it is extra nice to see her show some feelings, be a little happy and want something. Ironically, there are more maid-servants at the B-mansion in Borgarsandr than here in this mansion, but we don't need more maid-servants here, so even if they ask, we won't accept more. Frida seems to be working well as caretaker for the B-mansion, and can continue as such, but she might want to get radio training, which can be very useful if she is going to manage a property or mansion for us.

I take Asbjörn and Myrun aside, and bring them into the meeting room, and put Alith as a guard outside so we don't get disturbed. I've realised that if they start using more communications in the future, it's best that they use crypto, a crypto which I don't know the code to, so they trust what's being sent, who it's from and I shouldn't be suspected-blamed for reading it. Of course I hope they make some crypto mistakes that make it easier for me to crack their codes and read it, and it will be an interesting challenge to do so, but I want to help them avoid the easiest mistakes, and better they have a system I can't read, than a weakened one just so I can read it. If I can get the king to start using letters and mail etc, more people will adopt it and spread it. It is good both for binding the kingdom together and for increased communication, and showing how important literacy is.

Of course they already know the problem with sending messages, not least to verify that the message is from the sender it is said to be, and no one read it on the way or changed it. A wax or clay seal is not safe if someone copies the seal, which they worry about. So I start to explain the value of a crypto and being able to send secret messages where you don't have to rely on the transportation method. A big problem here is that the runes doesn't have a truly fixed order or alphabet, and areas even has different amount of runes, and then add dialects. Some use two runes for a sound, or have a special rune for that sound, and runes can be slightly different. How do you make a working easy-to-use crypto without a secret table or document when everyone use different rune alphabets? We have solved it amongst my group because we use the same rune line and system, since many couldn't read, or very badly. For others, I have come up with a less than ideal solution with a crypto disc as an aid where the disc has the most common 30 runes. The disc has 30 fields, which is one field every 12th degree, and it has a simpler moving arrow markers on the edge. A similar disc centered on the same axis can rotate and has the same order and runes as on the first. The crypto key is a simple runic code line where the code is a string of runes and you move backwards from the letter when you encode, and forward when you decode, and the key repeats until the message ends.

I have made a simple crypto disc prototype out of wood and written runes in ink so wheel can be shown and they can try using it. The disc is not really secret, although of course it complicates decoding if the enemy does not know the order of the runes, but the rune key is secret and can be memorised. This crypto is not 'good', partly because the runes is in a fixed order, but a longer rune key makes it difficult to decode, and will probably be good enough for the time being because it avoids a lot of the simplest mistakes in the simplest cryptos. Once they learn the order of the runes and get used to it, they don't even need to use the disk, everything can be done by hand, and they can get a better crypto in the future. Then there is the issue of dialects and getting them to spell words in the same way.

Both Asbjörn and Myrun like it, and it's not hard to get them both to practice it with short messages, and to make it easier as they learn, they use a four-rune word as the code key. They like that as long as both sender and receiver know the rune alphabet and keep the key in their heads, it becomes very difficult to decode and looks like nonsense. As a valuable bonus they also know that the message comes from the other person who knew the key - the senders name can be in plaintext at the beginning, where the code verifies that it is actually correct. I give them some tips like having different rune keys in correspondence to different people, so that someone who knows the system has no idea which key two other people are using. I also advise them to exchange new keys when they meet depending on how much the previous key was used, and that messages that are short are more secure. I tell them there are more secure crypto systems, with more steps in the decoding or with much more complex mathematics or require you to have, for example, a secret book filled with codes. But then, if you don't have that book available or if someone secretly copy the book... I don't need to say more than that.

They are crypto newbies, without even a proper common alphabet and with a crazy number system, in a world where most people can't read, including some Jarls and Storman. They have to start somewhere, and as expected, they really like that the real secret which is the key, can be kept in their heads and easily replaced. As long as nothing is written down about the system, not even how it works, it helps the secret, and they can do the work of encryption and plaintext conversion themselves without help from servants or others. I can get Digraldi to make brass copies of the discs divided into pieces, and camouflage its purpose as something else. Digraldi does so many strange things to me that he probably won't even ask what it is or for, and that goes for most craftsmen I hire. Asbjörn and Myrun have only seen a small part of everything I've had manufactured, and a lot is 'strange'. If the crypto discs are finished next time we meet, I will give them to Asbjörn, so he can pass them on to those he thinks should have them and teach them the system and invent a code key. Asbjörn really wants me to try to get it done for the Northmen Ting at the end of February because many people will gather there from far away, especially his allies, and he can then easily spread the system to those he wants.

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Myrun asks how safe I think it is, so after I explain how difficult it is to answer that question with 'how round is blue?', I just say I can give them a rough example of the amount of combinations and the time to test them all, and use a slate board to figure it out. Basically the brute force way. I say that each extra rune in the code key increases the time it takes to try it out by 30 times, and I give examples if you need 18 plain text runes to be able to see that you have found the right code, for the code to have repeated itself at least 3 times.

If an operation takes two heartbeats, i.e. 2 seconds, and the code key is a single rune, it takes about 2 x 30 x 18, i.e. 1080 heartbeats to decode the message in the worst case and 540 on average, because the first rune you try can be right, just as well as the last, so around 7 minutes, an eighth of an hour, but the code is so simple that you will discover it in less time. They get it and don't think it's particularly impressive. So I continue that if the code key is two runes, it will be about three hours. Three runes 5 days. Four runes 4 months. Five runes 10 years. Six runes 300 years. Where a person never sleeps and just tries by hand, combination after combination. Even if 100 people sit and try combinations at the same high pace half the day, week after week, month after month, an 18-rune message coded with 6 random symbols takes an average of 6 years to crack, even if any message with that code can then be read. If you then change the code key after a year, they just have to start over, for all hundred people, if they don't want to read what was written a few years ago. From just looking at the messages, they will not know that the code key has been changed, and the code key is only valid between two people if everyone uses their own code key. If messages from several people or with changed code keys are mixed, the correct code key A may be tried on a message that used code key B, C or D, and with that the code is never cracked even after they have tried all the combinations, because they 'tried' every code, not knowing there were several. And those keys might have different length. If they try a code key that is, for example, five long against a code key that is six runes long, there will be a mismatch, and only when it overlaps will the plaintext appear, and that might be tricky to notice and understand. It's basically a waste of time because message encoded with six characters only the first five match, and then only after thirty characters there are five more that are correct. Those who try to crack the code may not even understand why it failed.

Asbjörn and Myrun's expressions are quite amusing.

What I've said is not entirely true, especially in long messages where regularity analysis can start to be done and with other cryptographic weaknesses like bigrams and user mistakes and maybe a weak key. I also have a damn fast computer, but explaining what a computer is and can be programmed to do is a whole other shock. It will be an interesting challenge to make a brute force code-breaking program in the future, with a database based on words, but with a fairly simple crypto system with relocations and other things, the tablet computer hardly helps. And the tablet will not survive forever. Good manual code breaking will be important.

To get Asbjörn to test how difficult and frustrating it can be to crack a code when you have to try all the combinations, I ask Myrun to write a short secret message of about 20 runes, a few words, and use a code key of only four characters. Then Asbjörn can use all the time he wants until Northmen's Ting to try to crack the message by trying, and I give him the prototype disc. But there is a chance he will succeed, because the key may be near where he starts and he knows it's only four characters. Regardless, he will feel a little safer sending messages with the crypto system, and especially when the code gets longer because just a six character code has 900 times more combinations than the one he will try to crack. Myrun is so happy to do her part, and Asbjörn looks unhappy and grumpy, because he guesses it will mostly be terribly frustrating and a complete waste of time, but he wants to try and gain experience by trying to crack it. I'm right that it will feel better. But he wants Myrun to try and crack a message too, so Asbjörn will code a message for her to try. It's not hard to make another crypto disc, as just knowing the runic alphabet is enough.

It's the last night before guests leave and it's cold and damp outside, so safe to light flying paper lanterns, and in the cold clear winter night we watch as they slowly ascend. Just nine simple lanterns, but it's effective, beautiful and so appreciated. Good suggestion by Jane, and she came up with it when she started thinking about Disney movies and her favourite which is 'Tangled'.

Even the Elves know that heat collects at the roof and it is cold at the floor of a house, so this is an interesting lesson and proof that warm air is lighter than cold air and rises. I whisper to Iselin that among the first the ways humans flew were with very large hot air balloons. Which was dumb to say, because now I probably have to try and build a damn big balloon...

This evening Iselin brings Kari into my bedroom, as she once previously this week brought Ciara. It feels like Iselin is concerned, that just because she is now my wife, everything hasn't changed between all of us. Frankly, it's rarely been the three of us in a bed during sex and they're basically tag teaming me, but that is nice and Kari clearly likes being included. Iselin wants to try a bit of simple bondage with cloth tied around her wrists and a blind fold which is special for her, while for Kari it is simple and more sensual than what she usually wants to do. It feels quite absurd to have them both tied up beside each other on my bed.