The ancient Greeks in 500 BC used a famous encryption method. What's its name?

Scytale password

The earliest application record of cryptography in history is about the 5th century BC. At that time, Spartans in ancient Greece used a stick called scytale to transmit encrypted information. In scytale, Spartans would hover on a piece of parchment or leather. The sender wrote the relevant information horizontally on the wrapped parchment and then tore it off, so some meaningless alphabetical order appeared on the parchment. If you want to decode this message, the receiver only needs to wrap the parchment around a stick with the same diameter again, and then he can read the contents of the letter.

There is a story like this: In 404 BC, Lysander of Sparta met an emissary who came back from Persia. Only one of the five of them came back from this difficult journey. The messenger took off his belt, and Lysander rolled it on the sickle. After reading the letter, he knew that the Persians were going to attack him and made preparations in advance.

In a book I have read before, there is another version (mostly without any historical basis): there was a slave in ancient Greece who had to go through a barrier, and the Spartans checked it and found nothing wrong. Just as he was about to be released, a general suddenly found letters engraved on the slave's belt, so he took the belt and looked at it. He found that these letters were messy and had no clue. When he unwittingly rolled up the belt, he discovered the secret on the belt, and suddenly these letters were arranged in a regular way. In this way, the general discovered the enemy's plot and the slave was executed.

In fact, there is essentially no difference between scytale password and fence password.

You can try to write down the scytale password with a slender rectangular piece of paper and a hexagonal pencil. For example, I wrote a sentence, and after taking off the paper, I got the following ciphertext:

stte _ _ erh _ _ _ noe _ _ _ DOB _ _ _ MPR _ _ _ OSI _ _ _ RTD _ _ eog

Here _ is used to represent spaces, because a pencil has only six sides, so we know how many spaces there are. (You can usually omit spaces, or you don't know how many spaces there are. But we will find that unless the whole note is full, there will always be spaces, which also brings convenience to our segmentation when decoding. ) Because the key k=6 is known here, the following appearance is obtained by segmenting with six lines (including spaces):

stte_ _

erh_ _ _

Date: Year Month Day

mpr_ _

osi_ _ _

rrtd_ _

eog

Then, from top to bottom, column by column, we get the clear text: sendmoretroopstothebridge.

(Send more troops to the bridge)

There are two winding directions here, one left-handed and the other right-handed. If the note scrolls in the opposite direction, such as writing with the left hand and reading with the right hand, then the content of this message will be read from right to left. You can try. Xb 1r2YD HV:i

In addition, if it is written in another winding direction, it is the same as the above sentence. After taking off the note, you may get the following ciphertext: `vyf/l, ia f.

ETI _ _ _ RSR _ _ _ opb _ _ _ moe _ _ _ dohe _ _ nrtg _ _ etod _ _ sy5tkK！ ~gv

The key k=6, so we still use six lines (including spaces) to get the following appearance.

eti_ _ _

rsr_ _ _

opb_ _ _

moe _ _ _

nrtg_ _

etod_ _

How can we get clear text at this time? Haha, on the other hand, from bottom to top, one column after another, you get plain text:

sendmoretroopstothebridge

Give everyone an exercise.

Exercise 2. The following is a sentence I wrote with a piece of paper wrapped in a ham sausage. The ciphertext is as follows: