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asked in Computer Networks by Loyal (6.2k points) | 78 views

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Digital signatures can be seen as actual signature with an added feature of immutability.
In other words, if you sign a document and get laminated, it assures a reader that you have authenticated it but it also means that anybody can read it but cannot change what you have written.
Hence confidentiality deals with encryption and decryption. Authentication deals with assurance that a message is generated by the undersigned authority.
answered by Active (3.3k points)
How do we know that this signature belongs to an authenticated user only , means where do we maintain the record that which signature belongs to which user ?
If that's how it worked then it would need every user to get his signature registered with the database company and would involve a lot of other drama.
A better way out is,
The sender encrypts the msg with his PRIVATE key and since anyone can find the public key of any other person anytime, they can unlock the msg with the PUBLIC key of the sender.
Not to be confused with confidentiality because in case of confidentiality the sender encrypts the msg with the PUBLIC key of the RECEIVER so that only the receiver can unlock and read the msg with receiver's PRIVATE key.

Ok got this point , can you please explain the last statement in this paragraph , how the public key changes with time ?


It doesn't happen automatically.
If in case my private key is compromised, I would want to change it, and if you see the RSA algorithm, to change one's private key means changing one's public key as well.
And as explained in the book, this method isn't safe for disputable communications it is advised to have a trusted party which would solve the possible disputes.

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