What?

Encryption where everyone that wants to read the message, has the same key.

What makes a secure encryption?

  • Ideally an enemy can’t make their own secret key.
  • Ideally an enemy can’t recover the entire plaintext m.
  • Ideally an enemy can’t recover any of the plaintext m.

The attacker may have access to:

  • Some plaintext
  • Some cipher text / plain text pairs
  • They may have access to the encryptor (encryption oracle) that can encrypt plain text.
  • They likely would only have a realistic amount of compute.

WTF do we do with Keys?

Good question lol.

What’s Malleability in Encryption:

If an attacker can change the ciphertext in such a way that it predictably changes the then decrypted plaintext, the encryption is malleable.