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12:24 PM
Lecture No. 2
Comparison
between Symmetric key and Asymmetric key Cryptography
Encryption can be considered as electronic locking while
decryption can be thought as electronic unlocking. The sender pass the message in
a box using a key and the receiver unlocks it with the key and takes out the
message.
So in symmetric key cryptography same key is used for
locking and unlocking while in asymmetric key cryptography two different keys
are used one key for locking and another key for unlocking.
Symmetric key cryptography (in detail)
Symmetric key Cryptography started thousands of years ago
when people needed to exchange secrets. We still mainly use this one in our
network security.
Today’s ciphers are much more complex. First we will discuss
about traditional ciphers or algorithems which are character oriented. After
this we will discuss the modern ones which are bit oriented.
Traditional ciphers
These are character oriented although these are now absolute;
the goal is how modern ciphers evolved from them. We can divide tradition
symmetric key ciphers into two brand categories
Categories of Traditional ciphers
11.
Substitution
ciphers which is further divided in Monoalphabatic and polyalphabetic
substitution ciphers.
22.
Transposition
ciphers
These are two main categories of
traditional ciphers will be discussed in detail in next lecture.
Continued ………
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