Security and cryptography

Comment 1:

Security is a “system” concept.

Follow-up:
Yes it is very important for us (the users) to understand this so that we will not have a false sense of security when we are “educated” that our data are encrypted. Now you know that data encryption is just part of the whole process. Anything goes wrong in other parts of the system, security cannot be promised.

Comment 2:

HTTPS protocol?


Follow-up:
This is the so-called “secure” version of the HTTP protocol. Basically, this protocol transports
encrypted data instead of sending data in plaintext. The data is usually encrypted using a symmetric key system for which the shared key has to be agreed using a public key approach. Please refer to Problem 3 of Tutorial 5 for the design of such a key set-up protocol.

Comment 3:

Stealing bank account information from the Internet?


Follow-up:
Yes whether you like it or not, this kind of things are believed to be happening all the time! The thing is it is not very difficult to identify a “weakest” link in the system (e.g., a particular e-commerce Web site). It is widely believed that after such a system is broken, the hacker will not just use the bank account information (e.g., for buying things) but he/she will hold the bank and/or the e-commerce Web site for ransoms.

Comment 4:

What is symmetric key cryptography?


Follow-up:
Symmetric key system has always been the most important way for data confidentiality, despite that public key system is shown to be more versatile and “strong”. The reason is that symmetric key algorithms are usually much much faster than the public key algorithms. In a typical symmetric key system, a shared key has to be agreed upon through some means (see Comment 2 above). Then, the communicating parties will use the shared key for doing encryption/decryption.

Comment 5:

Are there any more sophisticated cryptography techniques?

Follow-up:
One of the most notable sophisticated cryptography techniques is the elliptic curve cryptography,
which is based on yet another branch of mathematics (also related to number theory) to perform
encryption and decryption.

Comment 6:

Public key cryptography. RSA algorithm?

Follow-up:
We have already worked extensively on this in Tutorial 5.


Comment 7:

Difference between public key and symmetric key cryptography.


Follow-up:
The most important difference is, NOT the strength, but the way keys are distributed/shared.