Lecture24

Before 24th lecture we learn about:
what is Cryptography?
we
had learned that cryptography is a technique to make data in
non-understand able form, in this way we can save our data from
unauthorized persons/factors.
How we can do Cryptography?
we
had done a practical for learning this thing. We had Encrypted our mail
then decrypt our mail. hopefully You people still remember.
How many types of Cryptography?
we had learned that there are two types of cryptography
1. symmetric
2. asymmetric

in symmetric same keys are used for encryption and decryption (we also had seen hows it happened. )
in asymmetric pair of private and public keys is used for encryption and decryption.

hopefully, you all people remember these all things.

after that we had learned what is digital signatures and I also made digital signature for explaining this concept.
with this we had learned about digital certificates and CA (certification authority),

we also know what is the process of sending messages using public key cryptography
and hows keys works in encryption and decryption.

In 24th lecture:

1st you had seen about symmetric key algorithms, here nothing to
explain so we just have to read this topic and same you people would
read.

2nd topic is here in notes: Attacks on symmetric key algorithm

here in our notes only 3 types of attacks are mentioned, I try my best to explain a little bit each of them.

Key Search Attacks:
May
be most of you people listen about Brute force/Brutus. well some people
may be not know about this, so i think I explain it too.
Once there
was a software which had known as Brutus via that software people may
crack others email accounts/windows passwords and other types of
securities. But now this software is banned in whole world. this
software was negative use of brute force. Brute force you may say a
technique or a method or u also may say a program. which search very
fast. if you have a 6 character password then may be it takes less then
6 seconds to expose your password.

well Key search attacks are
also harmful for us. because in this way unauthorized factors may
search our key and decrypt our message or data.

Cryptanalysis:
Cryptanalysis (from the Greek kryptós, "hidden", and analýein,
"to loosen" or "to untie") is the study of methods for obtaining the
meaning of encrypted information, without access to the secret
information which is normally required to do so. Typically, this
involves knowing how the system works and finding a secret key. In
non-technical language, this is the practice of password beaking or
cracking.

System-Based Attacks:
In this
attack, actually it will not be attacked on algorithm but it is made on
cryptographic system that uses the cryptographic algorithm that is
harmful for cryptography.

next topic is about Public Key Algorithms, it is just for reading, here nothing to explain.

well our next topic was Electronic Payment Systems, I think it would be revised with lecture 25th.



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JIN