Wednesday, July 28, 2021

Symmetric Key Distribution using Asymmetric Encryption

 

There are two approaches:

1.    Simple Secret Key Distribution

If A wishes to communicate with B, the following procedure is employed: A generates a public/private key pair {PUa, PRa} and transmits a message to B consisting of PUa and an identifier of A, IDA. B generates a secret key, Ks, and transmits it to A, which is encrypted with A’s public key.

A decrypt message using, D(PRa, E(PUa, Ks)) to recover the secret key. Because only A can decrypt the message, only A and B will know the identity of Ks. A discards PUa and PRa and B discards PUa. A and B can now securely communicate using conventional encryption and the session key Ks. At the completion of the exchange, both A and B discard Ks.

Figure : Simple Secret Key Distribution


2.    Secret Key Distribution with Confidentiality and Authentication

A uses B’s public key to encrypt a message to B containing an identifier of A(IDA)and a nonce (N1), which is used to identify this transaction uniquely. B sends a message to A encrypted with PUa and containing A’s nonce as (N1) well as a new nonce generated by B(N2). Because only B could have decrypted message (1), the presence of N1 in message (2) assures A that the correspondent is B. A returns N2, encrypted using B’s public key, to assure B that its correspondent is A. A selects a secret key and sends M = E(PUb, E(PRa, Ks)) to B. Encryption of this message with B’s public key ensures that only B can read it; encryption with A’s private key ensures that only A could have sent it. B decrypt the message and get secret key Ks. The result is that this scheme ensures both confidentiality and authentication in the exchange of a secret key.

Figure : Secret Key Distribution with confidentiality and authentication



    To learn more about Symmetric Key Distribution using Asymmetric

     Encryption,watch below video


Video : Symmetric Key Distribution using Symmetric Encryption

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