Cryptography 101

🛰️ Check it Live!

Decode

curl --request POST \
  --url http://infinite-bayou-68203.herokuapp.com/decode \
  --header 'content-type: application/json' \
  --data '{
	"msg": "UHCD KNOAOA PA MLG UYJX TOWBGR RF JWIIMSOBW VRFRII MA WHV WUQOITLY. ZJ UHG LYTV GVV APXMT LFZQZ CNKAF RN ZV, RQLW VAY RVRUKVPVDNJ IVWWFAX!"
}'

Encode

curl --request POST \
  --url http://infinite-bayou-68203.herokuapp.com/encode \
  --header 'content-type: application/json' \
  --data '{
	"msg": "Look Ma, im online!"
}'

Intro

We at Backend Architecture just discovered an alien civilization, and are orchestrating with them a world domination masterplan.

To avoid being caught by the authorities, we developed a cypher that will encrypt / decrypt the communications with them.

How does the cypher work

The cypher has a key, which we shared with the alien civilization. They key is used to encode the different characters of the message we want to send.

This is a version of the CAESAR cypher, with the difference that each character is encoded using a different value in the cypher key.

For the first character of the message, the cypher will use the first character of the key. Then the second, and so on.

The Problem

Given the cypher key (BACKENDARCHITECTURE) and an encrypted message, please provide the unencrypted version of the message (ie: build a function to decrypt messages)

Encrypted Message: HO KC EJHSFOL, IGH TXUCPZ FWX XB SLRA DQML

Bonus

Now that you know how to decrypt lets build an encrypt function that does the opposite thing.

Now send us an encrypted message!

Notes

Everything is in uppercase (A to Z).
Take a look at what a rune is, this could simplify your life for this exercise (or not 🧌)

imarune := 'A'
imarunetoo := "string"[0]
iamstillarune := uint8(66) // Before it said int32(66) and this could be missleading