At start you are are looking for a Mifare ultralight NFC.
Both newer Iphone and Android should be able to read it.
UID: 0449337A744C81 (not to be used, just to confirm you get the right NFC).
Text/number: A????????????1 (use this as the key, including A and 1).
Encrypted and base64 encoded hint and final coordinate:
BSkoMjQ8NVhKSxgWX142ZiUqNSYxQxhWUVdBETEvNiBpaBoEDRgABR0EdX9mAHd5ZhELDBoOBgk=
The coordinate and hint are encrypted using a xor_encrypt function defined as:
message: a string representing the plaintext message to be encrypted.
key: a string representing the encryption key of arbitrary length.
The function implement a basic XOR encryption algorithm. The function perform the following steps:
Initialize an empty string encrypted_message to store the result of the encryption process.
Obtain the length of the key.
Iterate over each character in the input message.
For each character, obtain the corresponding character from the key by cycling through it using the modulo operation with the length of the key.
Perform an XOR operation between the ASCII value of the message character and the ASCII value of the corresponding key character.
Convert the result of the XOR operation back to a character.
Append the encrypted character to the encrypted_message string.
After iterating over all characters in the input message, return the resulting encrypted_message string as base64.
Example:
key = "ABC123"
Base64 encrypted "Tirsdagsklubben": FSsxQlZSJjEoXUdRIyct