Elfcryption

gpg is used to encrypt file
Symmetric encryption [ie, same key to encrypt and decrypt]
gpg -e filename  --> encrypt with a password
gpg -d filename.gpg ---> decrypt using same password

md5sum data.txt --> it will give you a hash value of that file.
Try updating the files content and running the command again on the file, it will be different.
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Let’s generate some public/private keys and encrypt/decrypt a message!

To generate a private key we use the following command (8912 creates the key 8912 bits long): openssl genrsa -aes256 -out private.key 8912

To generate a public key we use our previously generated private key: openssl rsa -in private.key -pubout -out public.key

Lets now encrypt a file (plaintext.txt) using our public key: openssl rsautl -encrypt -pubin -inkey public.key -in plaintext.txt -out encrypted.txt

Now, if we use our private key, we can decrypt the file and get the original message: openssl rsautl -decrypt -inkey private.key -in encrypted.txt -out plaintext.txt

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Task

• What is the md5 hashsum of the encrypted note1 file?

  24cf615e2a4f42718f2ff36b35614f8f
  

• Where was elf Bob told to meet Alice?

  Santa's Grotto      --via gpg -d note1.txt.gpg  [password: redacted]]
  

• Decrypt note2 and obtain the flag!

  [redacted challenge flag]