Question

1. Which of these is necessary before two parties can use a symmetric cryptographic algorithm?
   1. A key they both know.
   2. A one-time pad.
   3. A communication Channel
   4. None of the above.
2. How can two people realistically get a common key to use in a cipher?
   1. The algorithm automatically provides it
   2. Ciphers do not require a common key
   3. You can use quantum entangled elections.
   4. It can be done either meeting in person, or by a secure key exchange
3. What is the fundamental idea behind key exchange?
   1. Encryption and decryption can be done using different keys.
   2. One-time pads should never be re-used
   3. Quantum relationships can be used to create keys.
   4. Two parties can securely and privately create a shared key without having to physically and securely meet
4. What is a man in the middle attack?
   1. One where an adversary can intercept and modify messages in the system
   2. One where one of two parties is acting maliciously
   3. One where the protocol designer left a back door open
   4. None of the above.

Answer 1

1.a key they both know

Symmetric-key algorithms require both the sender and the recipient of a message to have the same secret key. All early cryptographic systems required one of those people to somehow receive a copy of that secret key over a physically secure channel

2.You can use quantum entangled elections.

Many important aspects of IT security rely on encryption and public key cryptography, which are essential for e-commerce and protecting secret electronic information.

These techniques are based in turn on mathematical algorithms that are very difficult to “break”. Modern algorithms with suitable key lengths (e.g. AES-128, RSA-2048, ECDSA-256, etc.) are not susceptible to brute force attack – even with massive amounts of computing power, they would take centuries or, in some cases, even longer than the lifetime of the universe to break.

However, it is possible to create unique algorithms for quantum computers (e.g. “Shor’s algorithm”) that dramatically reduce the time it takes to break these algorithms.

Symmetric algorithms used for encryption, like AES, are still thought to be safe (with sufficient key length – e.g. AES-256 or larger); however, current asymmetric algorithms like RSA and ECDSA will be rendered essentially useless once quantum computers reach a certain scale.

This will break nearly every practical application of cryptography in use today, making e-commerce and many other digital applications that we rely on in our daily lives totally insecure.

3.Two parties can securely and privately create a shared key without having to physically and securely meet

For two parties to communicate confidentially, they must first exchange the secret key so that each party is able to encrypt messages before sending, and decrypt received ones. This process is known as the key exchange.

4.One where an adversary can intercept and modify messages in the system

A man-in-the-middle (MitM) attack is when an attacker intercepts communications between two parties either to secretly eavesdrop or modify traffic traveling between the two. Attackers might use MitM attacks to steal login credentials or personal information, spy on the victim, or sabotage communications or corrupt data.