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Lec-83: Asymmetric key Cryptography with example | Network Security - YouTube
Channel: Gate Smashers
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Hello friends, welcome to Gate Smashers
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the topic is
asymmetric key cryptography
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or which we can also call public key cryptography
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there is actually a difference between symmetric and asymmetric
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keys
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symmetric means same key
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means same key we encrypt
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with same key We decrypt
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and this is the
biggest challenge in that
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if the same key is being encrypted and decrypted
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then how will the sender send it to the receiver
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because they will also have to share the key among themselves
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but here in asymmetric
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we use two keys
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one public key
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and other private key
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public and private means
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that
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if we talk about a network
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then all the people in a network
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will make two kisses one public and one private
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means if I talk let's say
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A and B Are two People
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are A makes his public key private key
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B will make his public and private key
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so if I talk about A
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then A made his public key
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A made his
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private key
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similarly B
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made his public key
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and B made his own
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private key
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then all the people in the network,
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What will the first thing do is
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will generate public and private keys
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and what is the funda of public and private,
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how are they
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related to each other,
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if I encrypt a message with public-key,
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then it can be decrypted with the same private key.
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And if I encrypt a message
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with a private key,
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with the same public key,
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then it will be decrypted
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from the same person's
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If i with the same key
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encrypt with the same public-key,
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it open's with the same private key.
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And if I encrypt with the same private
key
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and apply the lock,
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with the same public-key,
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it will open
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these two keys are in such a way
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are related to each other
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what happens next
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public, now republic means
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General public
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means that this key known to everyone,
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either I will broadcast,
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this is my public key
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in the network,
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Or any third party
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We give keys to an authorized certified person
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whoever wants to communicates with me
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will take my public key from that person,
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then public key and private key
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private key means that private
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means do not share to anyone
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now, Let us see how the communication goes,
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how the encryption is done,
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if A and B want to communicate with each other,
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then we will have 4 cases
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because we have
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Four methods
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then these 4 cases use this from
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let to any message A have to send
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To B
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here A
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I write here...
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A....
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encrypted the message
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with its public key.
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A encrypted the message with his public-key
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SO what happened.
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Think about it
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A....
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encrypted the message with his public-key
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And send it..
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now how will it be decrypted
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I have already said
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that if A is encrypted with public key
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then it decrypted with the same private key
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with its public-key Sent to B after putting a lock on it,
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even if it reached B,
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how will it be opened,
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no one can open it not even B?
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Or nobody can open
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if there is an unauthorized person on the way,
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he can do it or even b can't
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because it needs A's private key
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is A's private key then A has it
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so that means we can't use this case
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second...
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if the message
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with B's
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private key
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encrypted and send
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whose, B's private key,
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This is case One..
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this is case two
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i encrypt with B's private key
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how can i encrypt
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private key of B then B has it
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I don't have it
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i.e. this case is also
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invalid,
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we can't use it,
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what can be the third case,
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what can we have with the third case,
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lat's say that if I want to send the message
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and I have here used my Public key
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let say, I use my private
key
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I send it with private key..
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When B get this message.
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Than how will B open it..
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With my Public key.
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But be careful.
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Not only B have my public key.
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C, D, E, all have it.
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so that means B can open that message.
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Before that, maybe someone else can open that message,
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then there is no encryption
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and if the encryption is not done,
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then the confidence will not be achieved,
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so these three cases are invalid,
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which is the fourth and last case,
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If A
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want to send a message to B,
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that message,
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encrypt
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the fourth case,
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B's
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which is the public key of B,
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means the public key of the receiver,
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the person to whom you are sending the message,
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take the public key of the person
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And that The public key either broadcast to me
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or any certified fellow
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I will tell the third party that I want to communicate
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then give his public key
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and public key then shareable
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then I took his public key
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Encrypted
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and sent
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now how will B open it.
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his private key
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and that b private key is with
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whom b is with
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even if you C, D, E, try it on the way.
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then They can't open it, why...
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because B's private If only B is there
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then there is only one case which is most
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important used here for encrypt
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so the from the point of view of encryption
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important factor is
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always use the receivers public key
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always use the receivers public key
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to encrypt the message
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and how will the receiver open that message
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with his private key.
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open the message.
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this is the concept of asymmetric key cryptography.
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now in this which we use in real life
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RSA, this is one of the very important algorithm
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Rivest-Shamir-Adleman
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these three scientists together made the algorithm
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it's very secure algorithm
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which is used as asymmetric Algorithm
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So this has already come in GATE and UGC NET.
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also and let me tell you a small point
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we also discussed in
symmetric-key
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that if four devices
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re connected to each other,
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so, how many keys will be required
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in the case of symmetric,
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I said nC2 is the formula
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but what is the formula here.
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2N
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N is the number of nodes or device.
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let say A, B, C, and D.
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How can they maximum connected.
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From the way of the graph,
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because in the complete graph,
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there cannot be more edges
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then if we talk here A will make how many keys
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Two...
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B...
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Two...
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C..
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Two...
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D is Two..
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all it's private public private public
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then how much will be
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Eight...
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if here 2 into N
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how many numbers of nodes or device
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i.e. 8 keys
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where needed
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then basically
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this is whatever point you have to remember
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because It has already appeared in UGC NET
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and there are chances of appearing in upcoming exams
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so this is all About Basic of Asymmetric Key
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Cryptography
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If you like this video please like it
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THANK YOU...
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