Stream Ciphers: Security and Key Length

<p>Stream cipher</p> Signup and view all the answers

<p>Known-plaintext attack</p> Signup and view all the answers

<p>A known-ciphertext attack has little information and tries to find corresponding plaintext, while a known-plaintext attack involves the attacker being given a list of plaintext/ciphertext pairs and then trying to find the key or at least the plaintext for a given ciphertext.</p> Signup and view all the answers

<p>A chosen-plaintext attack involves the attacker being given access to an encryption oracle (Blackbox) and the goal is to find the key or just to decrypt the message. This attack is stronger than a known-plaintext attack because in the former, the attacker is given plaintext/ciphertext pairs, but in the chosen-plaintext attack, the attacker can generate the plaintext/ciphertext pairs that they want.</p> Signup and view all the answers

<p>In the context of public key cryptography, an example of a chosen-plaintext attack is when an attacker can send queries to a Blackbox (any plaintext) and the box can give out the encryption of this message. This is stronger than a known-plaintext attack because in the former, the attacker is given plaintext/ciphertext pairs, but in this black box situation the attacker can generate the plaintext/ciphertext pairs that they want.</p> Signup and view all the answers

<p>A practical cipher should have a key length much smaller than the message length in order to provide security against known attack techniques.</p> Signup and view all the answers

<p>A chosen-plaintext attack is stronger than a known-plaintext attack because in the former, the attacker can generate the plaintext/ciphertext pairs that they want, whereas in the latter, the attacker is given plaintext/ciphertext pairs.</p> Signup and view all the answers